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TVÄRMINNE
STUDIES
TVÄRMINNE STUDIES is published at irregular intervals by Tvärminne Zoological
Station, a field station belonging to the University of Helsinki. It will contain short
research reports in the form of abstracts. In order to receive it in exchange, please
contact the station.
Address: Tvärminne Zoological Station, FIN-10900 Hanko, Finland.
Telephone: +358 19 28011
Telefax: +358 19 280122
E-mail: [email protected]
Internet: http://www.helsinki.fi/ml/tvea
Editor: Jouko Pokki
Contents:
1. Introduction ......................................................................................................
2. Marine biology .................................................................................................
2.1. Littoral studies.........................................................................................
2.2. Pelagial studies........................................................................................
2.3. Benthic studies ........................................................................................
2.4. Physical environment..............................................................................
3. Population biology ...........................................................................................
4. Evolutionary biology........................................................................................
4.1. Aquatic studies ........................................................................................
4.2. Terrestrial studies ....................................................................................
5. Ecophysiology and ecotoxicology ...................................................................
6. Miscellaneous...................................................................................................
7. Scientific publications in the years 1997-99 ....................................................
8. Index of contributors and their e-mail addresses .............................................
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Cover: Viking Nyström
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1. INTRODUCTION
When the previous issue of Tvärminne Studies was published in 1997 we were just
finishing the planning of a thorough reorganisation of the laboratory building and two
new houses (50 m2 each) for summer time experimental work. Now, after two years of
intense use we can proudly tell that it all went well and we can offer better research
facilities than ever before. The doubling of laboratory space also means much better
working conditions for courses. However, merely keeping of an advanced field station
with modern laboratory facilities demands a lot of money year after year not to speak
about larger updating efforts. Is it worth all the expenditure used for it?
The quality of the research done at the University of Helsinki was assessed by international peer review panels in 1999. The panel for biological sciences was asked to
asses the significance of the three biological stations of the Faculty of Science in the
research environment of the University. In the final report the panel pointed out, that
(abbreviated citation) “areas of high-quality habitat for field work are necessary for
ecologists and other environmental scientists. But there are advantages in the maintenance of the Stations beyond this basic service. Large amount of good and high quality
research are produced at them”. After reminding of the large number of publications
the Population Biology Division of the Department of Ecology and Systematics, one of
the top-rated units in the assessment, aroused from the data collected at the Stations,
the panel also points at one of the most important advantage of the Stations: “The
facilities available attract valuable research contracts and overseas scientists, enhancing
the intellectual environment for all”. Likewise, the great importance of the Stations in
teaching of biology was explicitly stated in the report.
The panel also considered a scenario in which the Stations were discontinued. The
conclusion was clear-cut: “Much of the research could still be carried out elsewhere but
at much greater cost: in the construction of replicate facilities; in time spent in organisation of logistics and travel; in ensuring experiments were secure; in collecting
background data which is necessary and available for the areas around the stations
because of their permanency; and in prospecting suitable alternative sites.”
“Similarly the organisation of field courses in other locations is certainly possible, but
at much greater cost, for both accommodation and laboratory hire, and especially in
time costs for those organising them. ... And, of course, the cross-fertilisation of ideas
that occurs when large numbers of talented people are brought together for extended
periods would be lost.”
With the modernised laboratories and other facilities on one hand and the overwhelmingly positive assessment report on the other we feel confident in starting the new
millennium. As before, we welcome scientists – domestic as well as foreign, terrestrial
as well as marine – to take advantage of the facilities we have. And if you are planning
an international field course or workshop, please, don’t hesitate to contact the station to
get more information.
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2. MARINE BIOLOGY
2.1. LITTORAL STUDIES
GEORGE RUSSELL
School of Biological Sciences, University of Liverpool, U.K.
Winter hardiness in Enteromorpha intestinalis (L.) Nees
U.K. populations of E. intestinalis are reported to respond to the reproductive region of
the tallus. These cells evidently remain viable when adjoining tissues are killed and, by
developing into new plants, provide means of vegetative propagation as well as
survival. The aim of this study was to see if Baltic populations react to winter conditions in this way. The work was carried out at Tvärminne between 15 April and 5 May
1998. Six samples were investigated. The first of these was obtained from the shore
outside the Zoological Station and this material had been emergent for several weeks as
a result of a drop in water level in late March. The 5 remaining samples were collected
from rock pools at various levels in the geolittoral belt at Brännskär. The plants in these
had been permanently submerged or icebound throughout the winter.
The viability of the samples was determined by culturing excised 10mm lengths of
tissue cut from tallus bases. 25 replicate tissue portions were cultured separately from
each sample. After 5 days in culture they were inspected for the presence of rhizoids on
the proximal cut edges. The viability of the emergent population (i.e. able to form
rhizoids) was 36 % while that of the rock-pool samples was 76 %, 88 %, 92 %, 100 %
and 100 %. Mortality in the emergent population was significantly greater than in any
pool sample (p<0.01).
Areas of dead bleached tissue were common in the emergent sample and in two from
rock pools. Staining with basic fuchsin confirmed that most bleached cells had retained
their contents and had not simply become empty following spore release. Some green
cells were invariably present in otherwise dead tissue but these surviving cells proved
not to be larger than their killed neighbours. On the contrary, they were significantly
smaller (p<0.001) This is not really surprising as large cells are likely to be more
vacuolate and hence more liable to damage from ice crystal formation. 150 distal portions of thallus, bleached and otherwise, were cultured for 11–15 days and germination
of isolated green was occasionally observed. On the rather generous assumption that
10 % of the latter may develop into new thalli, their contribution to the overall
reproductive potential of the population was in every case less than 0.01 %. Winter
hardiness of Baltic E. intestinalis is therefore a property of the thallus as a whole and
no special reproductive mechanism is involved in, or necessary for, the survival of
geolittoral rockpool population in winter. Emergent population are evidently more
vulnerable but factors additional to low temperature may well be involved in the
observed tissue damage.
ARI RUUSKANEN1 AND MIKKO KIIRIKKI2
1
2
Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki,
Finnish Environment Institute
Experimental evidence that Pilayella littoralis controls the settlement success of
Fucus vesiculosus in the northern Baltic Sea
During the reproduction period of Fucus vesiculosus, hard substrates suitable for
zygote settlement are often covered by a thick carpet of a brown filamentous algae,
mainly Pilayella littoralis. The effect of P. littoralis -cover on the settlement success of
F. vesiculosus was tested by using a sequence of artificial substrates. The first
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substrates were set up to the study site during the reproduction period of P. littoralis in
October–December, and the last during the reproduction peak of F. vesiculosus in
May–June. The substrates exposed in October–December became covered by Pilayella
littoralis canopy which lasted over the settlement period of F. vesiculosus. The substrates exposed in January–June were practically bare during the F. vesiculosus settlement. Recruits of F. vesiculosus were later observed only on those substrates free from
Pilayella littoralis.
Eutrophication of the Baltic Sea has increased the biomass of P. littoralis during the
last decades. Simultaneously the area covered by the perennial Fucus vesiculosus
dominated vegetation has declined. Increase of Pilayella littoralis is not necessarily the
primary explanation for the decline, but it can explain the very low recolonisation rate
of Fucus vesiculosus after the decline. The recolonisation can be locally speeded-up by
providing the F. vesiculosus zygotes competition-free substrates. This can be done e.g.
by turning around subsurface stones or by deposing surface stones to the optimal
growing depth of F. vesiculosus during the spring months.
Does fluctuating salinity induce branching of Fucus vesiculosus?
During the field surveys in the Bothnian Sea, i.e. towards low salinity areas (approx.
4 ‰), we observed that the frequency of irregularly branched Fucus vesiculosus plants
increased. Salinity is known to decrease gradually towards the northern parts of the
Baltic Sea. However, salinity is not steady but may fluctuate greatly on an annual and
even a daily scale, and salinity can drop to zero for short periods.
In order to demonstrate whether fluctuating salinity induces irregular branching of F.
vesiculosus, an experiment was carried out in the Tvärminne archipelago, on the south
coast of Finland in May–September 1997. First, plants were collected and then put into
two containers both of which had a fresh water and a sea water flow through. After 48
hours of treatment the plants were removed to the same place where they had been
originally collected. After the growing season, the plants were collected again, and the
number of irregularly and normally branched tips were measured.
The results shows that plants with the fresh water treatment, has branched irregularly.
In contrast, the control plants had only a few irregularly branched tips. This experiment
allows us to conclude that low salinity during the critical growing season induces
irregular branching.
Publication: 1210.
ARI RUUSKANEN1, SAARA BÄCK2 AND TRIIN REITALU3
1
2
Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki,
Finnish Environment Institute, 3Institute of Botany and Ecology, University of Tartu, Estonia
A comparison of two cartographic exposure methods using Fucus vesiculosus as
an indicator of wave action on small and large geomorphological scales
Morphological variation and vertical distribution of Fucus vesiculosus has been
quantified at several sites in the archipelago. Fucus samples were obtained from
skerries at geographical distances of 1 km or more (large scale) and at intervals of ca.
100 m around a single island (small scale). The results have been examined in relation
to wave exposure calculated by Baardseth and Effective fetch cartographic methods.
Despite the fact that the exposure indices were calculated differently they correlated
strongly.
Vegetative morphological characteristics of F. vesiculosus illustrate the morphological
differences both within and between the exposure gradient. The tallest and widest
Fucus plants were found at the sheltered end of the large-scale exposure gradient.
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Those from equally sheltered sites of the island were smaller in all respects. Thus, the
trend from small narrow plants to large wide sheltered plants was expressed differently
over the different geographical scale. Consequently, localities with similar exposure
indices may have morphologically different Fucus populations.
Shores with similar cartographic exposure indices can be different in nature. Underwater microtopography and shore locations, either close to the mainland or in the
outermost archipelago affect the exposure. Although a sheltered shore is indicated, the
sublittoral zone may be quite exposed to the movements of water. In contrast, in an
open shore underwater rocks, boulders and shallow water areas can provide sheltered
microhabitats.
The depth range of F. vesiculosus exhibited two distinctive patterns. In sheltered sites,
around islands in the outermost archipelago F. vesiculosus can grow at a maximum
depth up to 5 m. In exposed habitats the belt gets narrower at maximum depth of 3 m.
In the archipelago F. vesiculosus is found in exposed sites at a maximum depth of 5 m.
The depth range is narrow in sheltered sites, F. vesiculosus reaching only depths of 2 m
or less.
In summary, plant morphology and vertical belt distribution are similar to each other at
the exposed ends of the both gradients, whereas, in contrast, the sheltered ends are
different.
Publication:
1. Ruuskanen, A., Bäck, S. & Reitalu, T. 1999: A comparison of two cartographic
exposure methods using Fucus vesiculosus as an indicator. – Marine Biology 134:
139–145.
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EVA SANDBERG-KILPI, 1RIGGERT MUNSTERHJELM, 1,2PETRI OJALA AND 1, 2CATHERINE HENRICSON
1
Tvärminne Zoological Station and 2Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki
Environmental conditions in shallow coastal lagoons – a methodological study
A two year joint EU Interreg II project on shallow coastal lagoons (flads) around the
northern Baltic Sea was carried out in 1998–99 in collaboration with Husö Biological
Station (Åbo Akademi University), Upplandsstiftelsen and Uppsala University Sweden.
The main aim of the project was to develop suitable methods for sampling macrophytes
and macrofauna in shallow coastal lagoons to be used in evaluating the state of the
environment. In the Tvärminne area sampling was done in six shallow lagoons representing three different successional stages. From each of the successional stages one
lagoon in natural state was compared with another affected by human activities (e.g.
dredging, agriculture). Macrophytes were sampled using both long and short transects
and a grid-transect method. For zoobenthos a core sampler, net sampler and the
Tvärminne sampler were tested. A comparison of the results obtained from all the
studied areas showed that the most suitable method for macrophytes was to use the
combination of long and short transects. A suitable method for benthos is yet to be
found.
The project also aimed at defining possible indicator species among macrophytes and
macrofauna (based on their distribution and abundance) to be used as criteria for the
assessment of the environmental quality of shallow coastal lagoons. However, more
data are needed for this purpose.
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RIGGERT MUNSTERHJELM
Tvärminne Zoological Station and Department of Ecology Systematics, Botanical Laboratory,
University of Helsinki
The aquatic macrovegetation of soft bottoms in the archipelago
Since 1978 I have investigated the macrophyte vegetation of more than 100 shallow
soft bottom localities on the SE side of Hanko peninsula including parts of Tvärminne
and Ekenäs archipelagos and the inlet Pojo Bay. These water plant habitats can be
grouped into different types of (1) bodies of open water bordered by the mainland
and/or islands, (2) shore sections, (3) coves, and (4) flads and gloes (coastal lagoons).
A description of the isolation process of flads and gloes from the sea and a
classification of the morphological stages of this succession (from juvenile flads over
flads and glo flads to gloes) has been provided recently1. I have also described 10
botanical flad or glo types which represent stages in the succession of plant communities.
The general environmental gradients from the more open to the inner parts of the
archipelago along with the isolation process of the flad makes it possible to study the
relation of waterplants to various combinations of environmental factors. The distributional patterns and successional processes along these gradients are mainly ruled by
decreasing salinity, increasing shelter, accumulation of gyttja (organic mud), rising
summer temperatures and, in the flad development, of natural oxygen shortage beneath
the ice in winter.
I have investigated most of the localities several times during the past two decades and
was thus able to observe some changes in the vegetation. However, my data (and other
contemporary studies, e.g. T. Heinonen) can be compared with the data collected by E.
Häyrén and H. Luther reaching from 1890s up to the end of 1940s. This gives an
extraordinary long time perspective to detect changes in the water plant occurrences.
Perhaps the most drastic case is Chara tomentosa which has totally disappeared from
or decreased in 30 of 37 localities. In at least half of the cases this could be connected
with dredging or other mechanical activities of man.
Publication:
1. Munsterhjelm, R. 1997: The aquatic macrovegetation of flads and gloes, S coast of
Finland. – Acta Bot. Fennica 157:1-68.
CATHERINE HENRICSON
Department of Ecology and Systematics, Division of Hydrobiology, and Tvärminne Zoological
Station, University of Helsinki
The impact of sedimentation and waterflow on Chara tomentosa and Chara aspera
and associated macrofauna
Charophytes are often the first waterplants to disappear from shallow bays disturbed by
eutrophication or dredging. Whether increased sedimentation or waterflow could be the
ultimate reason for this was investigated by field-sampling and aquaria experiments.
The associated fauna was also examined to get more knowledge of the ecological role
of the charophytes.
Samples were taken from Chara tomentosa and Chara aspera stands in bays which
represented four different developmental stages from exposed to almost closed. Within
each of the stages one disturbed bay and one relatively undisturbed bay were chosen. In
all of the bays five 30x30 cm areas were harvested, and five benthic core samples were
taken in the Chara-stands and five core samples were taken on bare sediment bottom.
The species of waterplants and associated macrofauna were determined and weighted.
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The biomasses of Charophytes appeared to be greater in undisturbed environments.
The Chara-stands were inhabited by a diverse macrofauna community.
The impact of sedimentation and waterflow were tested by aquaria experiments. Ten
shoots of Chara tomentosa were planted in each of ten aquaria. In three of them the
shoots were exposed to different degrees of waterflow, in three to different amounts of
sediment suspended in the water and in three to different amounts of sediment strewed
on the plants. One aquarium with no treatment served as a control. Plants in the sedimentation treatments became tall, weak and green with long branches. Those exposed
to streaming water became short, robust, red and bowed with short inward-bent
branches. Some of them broke. The algae would probably not stand both streaming and
muddy water at the same time. Further investigation will still be carried out.
The Chara-communities have a great ecological importance serving as food and shelter
for many animal species. Because of their sensitivity to sedimentation and waterflow
their environments should be protected from mechanical interferences.
SAMULI KORPINEN
Department of Ecology and Systematics, Division of Hydrobiology and Tvärminne Zoological
Station
The complex structures of Gammarus-communities
Gammarids (Crustacea: Amphipoda) are a very abundant group of Baltic macroalgal
belt fauna. Their importance to the littoral food-web as prey, and also as omni-herbivores, can not be overestimated. However, little is known of their species-level interactions in The Baltic Sea.
The object of this study was to find out the microhabitats of five Gammarus-species
within three belts of macroalgae. The basic assumption was that gammarid communities are structured by depth, exposure of shore and macroalgal vegetation. The microhabitats of species G. duebeni, G. locusta, G. oceanicus, G. salinus and G. zaddachi
probably differ in the above-mentioned factors and life-cycles. Different life-cycles of
the species can be a way of coping with over-lapping niches.
The study was carried out in the Tvärminne archipelago on two sheltered and two
exposed shores. Gammarid samples were retrieved using two sieves, the diameter of
which depended on the belt of macroalgae. Species and life-stages were determined
and the length of each animal was measured.
The results show a complicated community. G. zaddachi exists most abundantly in
depth of 0–2 m and in the belts of filamentous and red algae. G. oceanicus is abundant
on exposed shores in the depth of 1–3,5 m in the Fucus belt. G. salinus prefers the
depth of 2,5–8 m in the belts of filamentous and red algae. The species is most
abundant on moderately sheltered shores. However, these three species were all found
within each of the three algal belts in the depths of 0–8 m. G. locusta is a rare species
living on exposed shores and G. duebeni is very seldom found outside rock-pools. The
different life-cycles of the species may be a crucial part of the microhabitat segregation.
Gammarus-species exist heterogeneously on the shores of Tvärminne. Depending on
the stages of their life-cycles, species occur in different depths and algal belts and their
abundance fluctuates. These factors should be taken into account in further studies.
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MATS WESTERBOM, MIKAEL KILPI, OLLI MUSTONEN AND JUKKA T. LEHTONEN
Tvärminne Zoological Station and Department of Ecology and Systematics, Zoological Laboratory,
University of Helsinki
Monitoring the occurrence of Mytilus edulis in the central and western parts of the
Gulf of Finland
Blue mussels in the northern Baltic Sea are among the dominant occupiers of space at
rocky bottoms. The Baltic blue mussel populations have traditionally been considered
as very stable, living near the carrying capacity of the area with regard to food and
space. Observations from the Gulf of Finland during the early 1990s however suggested a decline in average mussel size. In order to unravel the causes behind the
decline we started a follow-up study in 1996.
The study was done at exposed to semi-exposed rocky shores at three study areas
(Tvärminne, Rönnskär and Söderskär) along the southern coast of Finland. Sampling
(SCUBA) in the outer archipelago, was done at four stations/study area. Standard areas
of 0.044 m2 were randomly scraped from mussel beds at four depths (3, 5, 8 and 12 m).
From each depth three subsampels were taken (i.e. 48 samples/study area).
At the beginning of the research period an almost complete lack of larger mussels,
especially in the central parts of the Gulf of Finland, was documented. During 1997
and 1998 a slow recovery process occurred. Biomasses increased steadily at the study
areas. Also, size distributions showed recovery with a more diversificated population
structure. In 1998 a heavy recolonisation occurred in the whole Gulf of Finland which
during 1999 led to a considerable recovery in biomasses. The recovery has been fastest
at Tvärminne which today maintains blue mussel fields represented by dense,
moderately sized, blue mussels. Although the recovery-process has been fastest at
Tvärminne, also the other study areas show a steady recovery. We believe that changes
in salinity are the ultimate reason for both decrease and recovery among the blue
mussel populations.
MATS WESTERBOM, MIKAEL KILPI AND OLLI MUSTONEN
Tvärminne Zoological Station and Department of Ecology and Systematics, Zoological Laboratory,
University of Helsinki
Change in population structure of blue mussels along a salinity gradient in the
northern Baltic Sea
Populations of blue mussels in the northern Baltic are subject to complex regulations
posed by both physical and chemical parameters and biotic interactions. The low
salinity, that characterise the Baltic Sea, constrains the distribution of the mussel and a
salinity of 0.45 % has traditionally been seen as the ultimate limit of the mussel.
Although the effects of reduced salinity on Mytilus edulis populations clearly influence
both the distributional pattern and the population structure the responses of populations
along a large-scale salinity gradient are poorly known.
The change in size-structure of blue mussel populations was (1998) studied along
salinity gradients in the Archipelago Sea (Utö, Hitis, Hangö västra) and the Gulf of
Finland (Tvärminne, Rönnskär, Söderskär and Pellinge). We documented a steep
gradient in mussel structure over the entire study area. Moving from the west towards
the east, mean mussel size decreased, being highly skewed towards very small mussels
at the eastern rim of the study area. The difference between the Gulf of Finland and the
Archipelago Sea was remarkable. An illustrative example is the difference in sizestructure between Tvärminne and Hangö västra (a distance of 20 km). While blue
mussels that exceed 10 mm only constituted 1 % of the total population in Tvärminne
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the corresponding value was 25 % in Hangö västra. Also, 6 % of the mussels at Hangö
västra were longer than 19 mm, while only 0.03 % exceeded this value in Tvärminne.
We believe that the ultimate reason for the change is to be found from changes in
salinity, but we also believe that predation, mainly from the eider duck, has contributed
to the skewed population structure in the Gulf of Finland.
HEIDI SILLANPÄÄ, CHRISTOFFER BOSTRÖM AND JOHANNA MATTILA
Department of Environmental and Marine Biology and Husö Biological Station, Åbo Akademi
University
The importance of Zostera marina (L.) meadows for fish – a test of active and
passive sampling methods
Seagrass beds are generally considered as important habitats for fish, but this has never
been tested in Finnish coastal areas – the limit of distribution for eelgrass Zostera
marina in the Baltic Sea. The aim of the study was to quantify the importance of
seagrass meadows for littoral fish using active and passive sampling methods. To test
for possible spatial differences within localities, sampling was carried out in both
seagrass and adjacent unvegetated sand. The study was carried out at two localities:
Ryssholm (Tvärminne, SW Finland) and Hinderbengtsviken (Eckerö, western Åland).
Both localities were visited monthly during the period June–August (three sampling
efforts per locality). Sampling gears used were gillnets (mesh size: 12, 15, 20, 45 mm),
non-baited traps, push net, drop trap, haul seine and Ockelman sledge. In addition,
visual observations by SCUBA-diving along transects were made.
Preliminary results indicate that the sampling methods used produce different but
complementary results in both seagrass and sand. Total abundance and species number
were similar at both localities studied. Generally species richness was higher in
vegetation, but differences in abundance between seagrass and unvegetated sand varied
both temporally and with sampling gear. The seagrass beds in the areas studied seem to
support only few seagrass specific fish species, while several fish species common in
other shallow habitats seem to be able to utilize the food and shelter provided by the
vegetation.
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2.2. PELAGIAL STUDIES
RISTO LIGNELL1,2, ANNA-STIINA HEISKANEN1, PIRJO KUUPPO1, JUKKA SEPPÄLÄ1, OUTI SETÄLÄ1,
SANNA SOPANEN1, TIMO TAMMINEN1, PIRJO TUOMI1, AND TOM ANDERSEN3
1
Finnish Environment Institute, Impacts Research Division, 2Department of Limnology, University
of Helsinki, 3Norwegian Institute for Water Research
Persistence and stability of plankton food web structure and function following
short-term nutrient perturbations
In summers 1996 and 1998, two mesocosm experiments were carried out at Tvärminne
Zoological Station as our contribution to EU project COMWEB (PL950422). In the
July–August 1996 experiment (MESOBAL96), the design followed a linear increase in
mineral N and P additions in Redfield ratios, ranging from no additions (Control unit)
to 1 µM daily N addition (altogether 8 mesocosms, à 51 m3). By Day 5, spectacular
bifurcations with up to 100 % daily chla increase and biomass specific gross primary
productivity of 2–3 d-1 showed in units with high nutrient doses. Nevertheless, the
mean algal biomass responses over the 21-d studies were linearly related to N dose
with approximately 15 µg chla yield for 1 µM daily N dose. This suggests that despite
the early abrupt biomass changes the larger nutrient additions did not evoke any
‘systemic’ changes in the MESOBAL96 plankton communities. Microscopy examinations supported this view.
Respiration was by far the most important loss factor and showed a gradual overall
increase in proportion to nutrient dose. The areal P/R ratio (gross primary productivity
vs. total community respiration over the whole water column) showed a conspicuous
peak in all units on Days 5–7, ranging from ca. 2 (Control unit) to 6 (N dose 1 µM d-1).
After that, the P/R ratio declined to ca. 0.5 in all units, resulting in mean areal P/R
ratios close to unity in all units. The predominant alga in MESOBAL96 was the mixotrophic dinoflagellate Heterocapsa triquetra. One possible explanation for the dramatic
change in the time course of P/R ratio could hence be a switch from autotrophy to
phagotrophy by H. triquetra.
Sedimentation losses were small (5–10 % of respiration in all units). The sedimentation
measurements were supported by the high cumulative yields of added nutrients in
suspended particulate fractions (with P close to unity). Low sedimentation is typical for
the summer situation in our study area. The reason is that new nutrient inputs are not
channelled into diatoms (with high sedimentation rates) off the SW coast of Finland, as
is usually the case in upwelling areas, but into flagellated nanoalgae.
In MESOBAL96, the microbial food web (A1, H1 and H2) was not affected by the
nutrient additions (this concerned their biomasses, growth rates and grazing losses),
suggesting that the original microbial community was growing close to maximal rates.
Consequently, the nutrient load was transferred to higher trophic levels via enhanced
A2 and A3 productivity. Accordingly, their feeders H3 and H4 showed a clear positive
biomass response in proportion to N dose. The A2 biomass showed no net change over
the 21-d study period due to tight feeding control by H3 and H4. In contrast, feeding by
H4 was too weak to prevent a strong A3 biomass increase (this was both due to the low
initial biomass of H4 and their long generation times).
A flow network model based on four autotrophic (pico-microalgae) and four heterotrophic (bacteria-crustaceans) compartments was used to estimate the unknown flows
within the plankton community by the inverse method (IM). Introduction of viral lysis
of bacteria was necessary for finding an IM solution that was consistent with the
observations in MESOBAL96. Alternatively, the recorded ‘excess’ bacterial net
productivity could have been accounted for by algal mixotrophy (see above).
10
To study the effect of mineral N:P input ratios in the June–July 1998 experiment
(MESOBAL98), we choose two addition levels, one of which (0.3 µM N dose d-1)
evoked a linear (“toda controllada”) algal biomass response in MESOBAL96, while the
other (0.7 µM N dose d-1) resulted in an abrupt algal biomass increase (‘bifurcation’) in
the early phase followed by a virtually linear slow increase. Similar phytoplankton
responses were found in the corresponding units in MESOBAL98 despite the different
time periods and phases of plankton succession, suggesting that the community-level
responses were robust.
Like in MESOBAL96, bifurcations with sharp increases in chla and biomass specific
gross primary productivity were recorded in MESOBAL98 in units with high nutrient
doses. In MESOBAL98, the different N:P ratios in nutrient supply (ranging from 3 to
18, w/w) did not seem to evoke any major changes in the species composition of the
plankton community. Judging from the chla response surfaces, the phytoplankton
community was N limited during the first 15 days. Evidently, algae were relying on the
initially abundant ambient mineral P. After Day 15, the mineral P was exhausted from
the water column, and addition of both N and P was necessary to evoke a clear chla
response. Similarly with the 1996 results the mean algal biomass responses over the
21-d studies were linearly related to N dose with approximately 15 µg chla yield for 1
µM daily N dose. Surprisingly, a trichal cyanobacterial bloom doubled chla in all units,
including the Control unit, within 3 days after Day 18. The blue-greens probably
exploited stored P and satisfied their N needs via direct fixing of N2.
In 1998 like in 1996, respiration was by far the most important loss factor and showed
a similar pattern in both experiments with a gradual overall increase in proportion to
nutrient dose. However, contrary to the 1996 results, the areal P/R ratio (gross primary
productivity vs. total community respiration over the whole water column) fluctuated
around unity with no clear treatment effects in MESOBAL98.
In MESOBAL98 like in MESOBAL96, the nutrient load was transferred to higher
trophic levels via enhanced A2 and A3 primary productivity, their feeders H3 and H4
showing a clear positive biomass response as well. However, contrary to the
MESOBAL96 results also the microbial food web (A1, H1 and H2) showed predatorprey fluctuations in MESOBAL98. From the beginning, H2 biomass started to decline,
resulting in H1 and A1 increase. Relaxed feeding control allowed a clear positive
nutrient response of A1 biomass to evoke by the end of the experiment, whereas no
nutrient response was recorded with H1 and H2. The initial H2 biomass was ca. 4-fold
and H1 biomass ca. 40 % in 1998 compared to 1996. Possibly, in 1996 the initial
microbial food web was closer to steady state determined by input and output fluxes,
than after the upwelling event preceding the 1998 experiment.
11
RISTO LIGNELL1,2, JUKKA SEPPÄLÄ1, PIRJO KUUPPO1, TIMO TAMMINEN1, TOM ANDERSEN3 AND
INGRID GISMERVIK4
1
Finnish Environment Institute, Impacts Research Division, 2Department of Limnology, University
of Helsinki, 3Norwegian Institute for Water Research, 4University of Oslo, Department of Biology
Nutrient and grazing regulation of coastal summer plankton communities in the
northern Baltic Sea
In 1997, a field campaign carried out at Tvärminne Zoological Station was a part of our
contribution to EU project BASYS (MAS3-CT96-0058). Responses of main auto- and
heterotrophic pico- to microsized plankton compartments to removal of top predators
(<100 µm pre-screening) and nutrient treatments (all combinations of pulsed NH4 and
PO4 additions on Day 0) were followed for 3 d in 250-l transparent enclosures during
early summer ‘minimum’ (low mineral N) period, late summer blue-green algal bloom,
and early autumn nutrient upwelling event. Moreover, in vitro dilution experiments
were done to estimate phytoplankton growth rates and feeding pressure, as well as the
main nutrient sources for algal growth (external pools, intracellular stores, remineralisation) in the enclosures. The trichal blue-green alga Aphanizomenon flos-aquae
predominated in the early summer experiments and was important also in the others. A
significant chlorophyll a (chla) increase in all (pico-nano) size fractions was evoked by
single N addition in early summer and autumn while chla responded only to combined
N and P treatment in mineral N and P deplete late summer. Bacteria and heterotrophic
nanoflagellates seemed to be unaffected by the treatments, whereas ciliates showed a
clear increase in units with positive algal response. Accordingly, the protozoans exerted
a substantial feeding pressure on algae with minimum estimates of 0.05–0.3 d-1.
Internal stores were the most important P source for algae in mineral P replete conditions in early summer and in P units, while both internal stores and remineralization
were important N sources. Independent measurements (chla increase in enclosures,
dilution experiments, pigment labelling) all gave similar nutrient replete algal growth
rates of 0.2–0.6 d-1. In all experiments indicators like the particulate organic C:N ratios
and algal assimilation numbers suggested no serious physiological N limitation,
whereas signs of P deficiency were found during the blue-green algal bloom. These
results support our earlier findings of N limitation of phytoplankton biomass during
most of summer–autumn in our study area, and even during blue-green algal blooms
inputs of ‘new’ PO4 or high alkaline phosphatase activities seem necessary to enable
appreciable atmospheric N2 fixation to compensate for low N availability.
PIRJO TUOMI
Finnish Environment Institute
Virus dynamics in nutrient (N+P+Si) manipulated brackish water enclosures
Several factors affect the growth and death of bacteria, which can strongly affect the
fate of carbon and nutrients in planktonic ecosystem. The aim of this study was to
investigate virus dynamics in different nutritional conditions and the virus-induced
mortality of bacteria in two mesocosm experiments.
In the coastal area of the Northern Baltic Sea, 50 m3 seawater enclosures were manipulated with increasing concentrations of a nutrient mixture (PO4-P, NH4-N, SiO4-Si)
in summer 1996 and varying N:P ratios (2.9 to 18.0) in the experimental units in
summer 1998. Bacterial production was measured using thymidine incorporation rate.
Bacterial cell numbers were counted using epifluorescence microscopy. Bacterial cell
volumes, virus numbers and the fraction of bacteria infected with viruses were determined using electron microscopy.
12
Nutrient manipulation increased chl a concentration (from 2-3 up to 32 µg l-1) and
bacterial production (from 1 up to 5x108 cells l-1h-1 in 1996 and from 1 up to 20x108
cells l-1h-1 in 1998). Bacterial cell numbers ranged from 3 to 5x109 l-1 in 1996 and from
1 to 11x109 l-1 in 1998. Total virus counts ranged from 3 to 9x1010 l-1 in 1996 and from
3 to 18x1010 l-1 in 1998. Of bacteria, in 1996<0.05 to 0.8 % and in 1998 0.2 to 5.5 %
contained virus particles.
In 1996 experiment, increased algal density and bacterial growth rate did not stimulate
virus particle production. Any increase in virus numbers or in the fraction of bacteria
infected was observed only in the control unit receiving no manipulation. In the 1998
experiment, virus numbers increased with increasing chl a concentration, bacterial
production and bacterial cell numbers (r=0.655-0.675, p=0.001). During the 1998
experiment, the fraction of different morphological types among the infected bacteria
varied between the samplings. The magnitude of virus infection in the mesocosm
experiments may have depended on the bacterial community composition rather than
nutritional conditions or increased productivity of plankton ecosystem.
Bacterial and viral dynamics in microbial food webs of planktonic ecosystems
The effect of increased nutrient loading on bacterial and viral dynamics in planktonic
ecosystems was studied in 1993 using a large-scale (50 m3) experiment with nutrient
(N, P) and sucrose enrichments. Furthermore, bacterio- and virioplankton dynamics
was followed in the Gulf of Finland in 1994.
During the study in the Gulf of Finland, two methods to estimate bacterial production,
tritiated thymidine incorporation rate (TTI) and frequency of dividing cells (FDC),
were compared. TTI was transformed to cell production rate using empirical conversion factors derived from batch cultures of marine bacterial assemblages. Using data
from the same cultures, FDC was related to observed bacterial growth rates. Conversion factors for TTI varied largely, which was partly due to the different methods used
to calculate the factor. FDC was not found to correlate with bacterial growth rates in
batch cultures, and when applied to a field study in the Gulf of Finland this method
resulted in higher bacterial production estimates than TTI method.
In the mesocosm experiment in 1993, bacterial mortality due to viral infection was
estimated using the decay rate of virus particles as the virus production rate, and the
fraction of bacteria that contained mature virus particles. During the experiment, virusinduced mortality ranged from 8 to 808 % (average 239 %) or from <0.2 to 13 %
(average 7.5 %) of total bacterial loss when using the decay rates or fraction of infected
cells, respectively. Due to these large differences between the methods it was not
possible to conclude how a large fraction of bacteria was lysed by viruses in this
experiment.
In the mesocosm experiment in 1993, as well as in the Gulf of Finland in spring 1994,
the carbon fixed by blooming phytoplankton was channelled mostly elsewhere than to
bacteria. In 1994, a relatively greater material flux through the bacteria took place in
summer and late summer when compared to spring. During the growth season of 1994
in the productive water layer, bacterial carbon production was estimated to be 40 % of
net primary production. Thus, annually pelagic bacteria may process most of the
carbon fixed by phytoplankton. High bacterial production when compared to primary
production could be explained also by significant input of allochtonous carbon or
recycling of carbon several times through bacteria.
Publications: Nos. 1153 and 1216.
13
PIRJO KUUPPO1, KRISTINA SAMUELSSON2, JUKKA SEPPÄLÄ1, RISTO LIGNELL1, TIMO TAMMINEN1
2
AND AGNETA ANDERSSON
1
Finnish Environment Institute, 2University of Umeå, Departmenpt of Microbiology, Sweden
Limitation and control of the microbial food web at the Gotland Basin
Three experiments were run on two cruises in order to examine nutrient and carbon
limitation of picoplankton, channelling of the increased production of picoplankton, in
the microbial food web. In the 1997 cruise, predators were removed by filtration 0.8
µm from half of the experimental units while half of the units contained a natural water
sample. Nitrogen NH4-N, phosphate PO4-P and carbon glucose were added in 22
factorial design. In 1998, the water was prefiltered through 40 µm plankton sieve in
order to remove large zooplankton and larger aggregates. In the second experiment, the
water sample was first prefiltered with 90 µm plankton sieve, and then an inoculum of
ca. 40-fold concentrated >90µm plankton fraction was added to the experimental water.
The experiments were run in a deck incubator, where temperature was adjusted to in
situ by a continuous seawater flow, and the excess light was screened with a plastic
cover, allowing ca. 10–12 % per cent of the irradiance to pass to the experimental
flasks. Bacterial production, primary production and microbial biomasses were
followed during the 3-d experiments.
Picoalgal production was limited by both nitrogen and phosphorus, while bacterial
production was stimulated only with the combined CNP addition in all experiments
regardless of the year or blooming situation. Picoplankton biomass was controlled by
grazing. Increasing the production at the bottom of the microbial food web led only to
weak effects in the biomasses on the higher trophic levels, because of the cascading
grazing control in the microbial food web. Increase in the bacterial production by the
carbon addition, however, had a more visible effect in the higher trophic levels,
indicating a more direct link on the heterotrophic side, compared to the autotrophic part
of the food web.
ANNA UITTO1, HARRI KUOSA2, KAI KIVI1, RIITTA AUTIO1
1
2
Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki,
Finnish Institute of Marine Research
Dynamics of pelagic food web during algal and cyanobacterial blooms in the
Baltic Sea
During the summer, cyanobacteria and dinoflagellates can form occasional blooms in
the Baltic Sea. Toxic cyanobacteria are not directly grazed by metazooplankton, but
dissolved and particulate organic matter originating from degrading blooms may be
available for protists and metazooplankton through the microbial food web (MFW).
Vertically migrating dinoflagellates can form subsurface chlorophyll maximum (SCM)
below the thermocline, thus providing an additional food source for vertically migrating metazooplankton. The aim of this project is to I) develop tracer methods in
studying short-term feeding by proto- and metazooplankton on its naturally occurring
food, II) study the role MFW in metazooplankton nutrition during cyanobacterial
blooms and III) study metazooplankton grazing within the SCM maximum.
The studies were conducted at Tvärminne Zoological Station and during the cruises of
R/V Aranda in the Gulf of Finland in 1998 and 1999. In the experiments community
feeding by different size groups of metazooplankton and microprotists on stepwise
smaller natural autotrophic and heterotrophic food categories including algae, protists
and bacteria, were measured. The effects of fractionation procedure on food and feeder
categories were under special consideration. To study vertical variation in the com-
14
munity grazing rates, samples from the euphotic layer and the SCM layer below the
thermocline were used in the experiments.
In August 1998 the dinoflagellate (Heterocapsa triquetra) dominated phytoplankton
biomass in the Gulf of Finland. The experiments indicate that both the surface metazooplankton community dominated by podonid cladocerans and the SCM community
composing of calanoid copepods could feed on H. triquetra, but the bloom was not
regulated by metazooplankton grazing. Metazooplankton fed effectively on protists in
the surface layer. In August 1999 there was a clear cyanobacterial bloom in the Gulf of
Finland. Also in this case protists were important food for metazooplankton.
Publication:
1. Uitto, A., Kivi, K. & Kuosa, H. 2000: Vertical grazing of zooplankton during the
bloom of the dinoflagellate Heterocapsa triquetra in the northern Baltic Sea. –
American Society of Limnology and Oceanography (ASLO) 2000 Summer Meeting,
Copenhagen, Denmark, 5–9 June 2000 (abstract).
JUKKA SEPPÄLÄ
Finnish Environment Institute and Tvärminne Zoological Station
Bio-optical properties of Baltic Sea phytoplankton
During several experiments and field surveys I have focused on the variability of biooptical parameters. These include spectral chl a specific absorption of photosynthetic
and photoprotective pigments, fluorescence yield, variable fluorescence, the contributions of pigments and nonalgal fractions to the total light absorption, and what are their
relations to the algal taxonomy and physiology. The main aim is to provide basic information relevant for various field applications of bio-optical algal detection.
Spectral fluorescence signatures and variability of chl a specific fluorescence for
several algal species isolated from the Baltic Sea have been recorded. Obtained results
indicate potential of spectral fluorescence methods in the detection of chemotaxonomic
changes in the phytoplankton assemblages. As an example, basin-scale variation of
phycoeryhtrin fluorescence recorded from the Gulf of Riga in July 1994 was closely
related to the cyanobacterial abundance. This technique is further developed and utilised e.g. in 1997 and 1998 in the Gotland Deep during cyanobacterial blooms.
As noted in unialgal experiments, nutrient stress has not much effect on the shape of
spectral fluorescence, i.e. on the pigmentation of photosystem II or on the relative
electron transfer efficiencies. Low light increases the contribution of photosynthetic
accessory pigments from the total excitation spectra, when compared to direct excitation through chl a. Partitioning the spectral light absorption into components of dissolved matter, non-algal particulate matter, photosynthetic (estimated from scaled farred fluorescence) and photoprotective algal pigments has been carried out during some
field surveys and mesocosm experiments. Such measures provide information of the
actual amount of light available for algal photochemistry.
The future research will include (1) methodological improvements of bio-optical measurements, (2) studies of the effect of light adaptation and nutrient stress on the biooptical properties of bloom forming phytoplankton species, and (3) monitoring the
variability of bio-optical properties in natural phytoplankton assemblages. The detection and quantification of cyanobacterial blooms utilising phycobilin fluorescence
methods will be emphasised.
Publications: No. 1177 and
1. Seppälä, J. & Balode, M. 1998: The use of spectral fluorescence methods to detect
changes in the phytoplankton community. In: Tamminen, T. and Kuosa, H. (eds.),
15
Eutrophication in planktonic ecosystems: Food web dynamics and elemental
cycling. – Hydrobiologia. 363: 207–217.
2. Babichenko, S., Leeben, A., Poryvkina, L., Shalapyonok, A., & Seppälä, J. 2000:
Variability of Chlorella sp. fluorescence in response to different nitrogen conditions.
– Int. Journal of Remote Sensing (accepted for publication).
MIKA RAATEOJA1 AND JUKKA SEPPÄLÄ 2, 3
1
Finnish Institute of Marine Research, 2Finnish Environment Institute, 3Tvärminne Zoological
Station
Measuring the photosynthetic parameters of algae by variable fluorescence
technique
In the variable chlorophyll fluorescence methods the photosynthetic parameters of the
phytoplankton are estimated from changes in the fluorescence yield. The Fast Repetition Rate (FRR) technique utilizes a rapid series of excitation flashes and offers an
efficient way to study the photosynthetic activity of phytoplankton. We have studied
the FRR, 14C, and O2 approaches to the algal light utilization and primary productivity,
and completed them with spectral measurements to derive the rate of light absorption
by PSII. Furthermore, we have supplemented bio-optical measurements with growth
and nutrient uptake rates that give an insight into the changing physiological status of
the algae.
The photosynthetic performance of Nannochloris sp. (Chlorophyceae) batch cultures,
acclimated to 314 (HL) and 39 (LL) µmol quanta m-2 s-1, was evaluated in the course of
one light period. The growth rates in both cultures were mainly regulated by the
internal cell cycle, rather than by light and nutrients. Photosynthetic efficiency
measured with P-I curves, and FRR were correlated with r2=0.88 (n=5) in HL. The
fluorescence-based in situ primary production rate (Pf') was 15–45 % of the 14C-based
primary production rate (Pc) in HL. Low Pf'-values, compared to Pc-values, were partly
a consequence of the inadequate excitation delivery in the FRRF saturation protocol.
The different patterns of Pf' and Pc in the course of the study were mainly caused by the
inability of the variable fluorescence method to take into account a partial loss of ATP,
NADPH and ferredoxin pools caused by the active NO3- uptake and reduction. A
perspective was taken towards existing models in the variable fluorescence technique.
As the effect of active NO3- uptake was observed to lessen the ability of the fluorescence-based technique to measure primary production rates, we will study the relationships of various primary production methods more profoundly in different N-stress
levels. These studies will include species forming harmful blooms, as well as the
natural phytoplankton assemblages.
Publication:
1. Raateoja, M., & Seppälä, J.: Light utilization and photosynthetic efficiency of
Nannochloris sp. (Chlorophyceae) – approached by spectral absorption characteristics and fast repetition rate fluorometry (FRRF). – Submitted.
16
SANNA PEKURI
Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki
Effects of nutrient additions and zooplankton excreta on heterotrophic bacteria
and picocyanobacteria
A series of experiments was conducted at Tvärminne and onboard R/V Aranda to find
out (1) which nutrients limit the growth of heterotrophic bacteria and picocyanobacteria
in the pelagial waters of SW Finland from late spring to early autumn, and (2) the
effect of nutrients recycled by zooplankton. All experimental units contained seawater
filtered through 1,0 µm filter to remove larger plankton including grazers. In the
nutrient enrichment experiments the treatments were nitrogen, phosphorus and sucrose
addition. In the excretion experiments zooplankton (Mysidaceae) excreta were added.
During the two-day experiments the production of heterotrophic bacteria was measured
from tritiated thymidine incorporation rate sampled at 0, 24 and 48 hours.
Picocyanobacteria were enumerated with epifluorescence microscope.
Carbon enhanced the production of bacteria in each experiment except one, but in the
early autumn only with simultaneous addition of nitrogen. Picocyanobacteria were
nitrogen-limited in the early autumn. The groups did not have the same limiting nutrient at the same time and there was apparently no competition between them.
Zooplankton excretes increased the production of heterotrophic bacteria considerably
and the growth of picocyanobacteria in a lesser degree. There is no information about
the total effect of compounds released by zooplankton on the growth of pelagial
bacteria and picocyanobacteria, but it may be important when water is stratified and the
regeneration of nutrients is essential.
Publication:
1. Pekuri, S. 1999: Bakteerien ja pikosinilevien ravinnerajoittuneisuus sekä eläinplanktonin erityksen vaikutus kasvuun [Nutrient limitedness of bacteria and pico
cyanobacteria and the effects of zooplankton excreta on their growth]. – M. Sci.
Thesis. Department of Ecology and Systematics, Division of Hydrobiology,
University of Helsinki. 51 pp.
ANKE KREMP1 AND DONALD ANDERSON2
1
Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki, 2Woods
Hole Oceanographic Institution
The role of resting cysts in bloom initiation of the vernal dinoflagellate Scrippsiella
hangoei from the northern Baltic Sea
The role of cyst germination as a factor in bloom initiation was investigated for the
dinoflagellate Scrippsiella hangoei (Schiller) Larsen from the northern Baltic Sea. This
species blooms in very cold, often ice-covered waters, and is responsible for a
significant fraction of the production in that region. Dormancy, temperature, oxygen
and light were studied as factors potentially controlling the germination of S. hangoei
resting cysts.
Mandatory dormancy was the primary factor regulating the timing of germination in S.
hangoei. Cysts began to germinate in mid winter when temperatures in the natural
environment were within the favourable “window” (0–9 °C). Anoxia and darkness
maintained a state of quiescence in the cysts. Temporary exposure to high sulphide
concentrations reduced the germination potential, indicating that S. hangoei cysts have
a low resistance to oxygen deficiency. The results of a field study on the seasonal
dynamics of viable, empty and fluorescing cysts in coastal surface sediments showed,
that only a small fraction of the very abundant benthic cysts contribute to the initiation
17
of the new vegetative population. Chlorophyll fluorescence during the germination
period was observed in 5 to 25 % of the cysts from surface sediments corresponding to
the minor but significant increase of the fraction of empty cysts during winter. It is
assumed, that in the natural environment factors such as bioturbation and advection
further reduce the seeding potential of the species.
Publications:
1. Kremp, A. 1999: Life cycle and bloom dynamics in the vernal dinoflagellate
Scrippsiella hangoei from the northern Baltic Sea. – Lic. Phil. Thesis, Department of
Ecology and Systematics, Division of Hydrobiology, University of Helsinki. 16 pp.
+ app.
2. Kremp, A. & Anderson, D.M.: Factors regulating germination of resting cysts of the
spring bloom dinoflagellate Scrippsiella hangoei from the northern Baltic Sea. –
Submitted to Journal of Plankton Research.
3. Kremp, A.: Cyst dynamics and benthic seeding potential of Scrippsiella hangoei in
surface sediments of the coastal northern Baltic Sea. – Manuscript.
ANKE KREMP
Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki
The resting cyst of the bloom forming cold water dinoflagellate Peridiniella
catenata
The resting cyst of the dinoflagellate Peridiniella catenata (Levander) Balech, found
from sediments from the SW coast of Finland, Baltic Sea, is described. Additionally,
the germination pattern as well as the seasonal dynamics of benthic resting cysts and
planktonic cells were investigated. The discoid, colourless and thin walled cysts
germinated after a dormancy period of 6 months, resulting in vegetative cells which
were identified as P. catenata individuals. Synchronized excystment occurred in mid
winter at 2 °C, providing the prerequisites for a release of new vegetative cells at
favourable growth conditions in the natural environment. The decrease of cyst
abundances in the surface sediments coincided with the appearance of vegetative cells
in the water column and, reversely, the decay of the vegetative population was
followed by a massive input of cysts to the sediments. The formation of resting cysts,
the dormancy interval and finally the timing of germination seem to regulate the
seasonal appearance of P. catenata in the water column.
Publication:
1. Kremp, A.: The resting cyst of the bloom forming cold water dinoflagellate
Peridiniella catenata. – Submitted to Phycologia.
HARRI KUOSA, JUHA FLINKMAN AND HERMANNI KAARTOKALLIO
Finnish Institute of Marine Research and Tvärminne Zoological Station
Ice-related primary productivity and nutrient dynamics in Baltic sea ice
The project consists of two subprojects. One subproject studies nutrient dynamics in
seasonal sea ice in the Baltic Sea. Specifically different forms of nitrogen and nitrogen
cycle processes carried out by bacteria are investigated. Baltic sea ice contains high
concentrations of nitrogen compounds, including ammonium and nitrite. Presence of
these reduced forms points to active nitrogen transformations in the sea ice environment. Particulate nitrogen may be trapped during the freezing and algae may produce
ice layers rich in organic particulate matter. As nutrient regeneration is associated with
organic carbon mineralisation, dissolved inorganic nitrogen is trapped into the brine
18
channels inside the ice. Atmospheric input of nitrogen is also important controlling
factor in sea ice nutrient dynamics since wintertime precipitation accumulates on the
upper surface of ice and is partly flushed into the ice column. In March 1998 ice cores
were taken outside Tvärminne. The results showed different quantitative and qualitative distribution of nitrogen compounds in the ice column. Inner parts of ice are the
most obvious places for heterotrophic processes and nutrient regeneration, while an
algal bloom develops near the ice-water interface.
The other subproject studies phytoplankton communities and succession under the ice.
Hydrographic, nutrient and plankton samples were taken in 1999 by the aid of a diver.
Ice provided a barrier preventing turbulence under the ice. A phytoplankton community
very well adapted to low light environment developed already in midwinter. Another
community consisting of larger algae adapted to somewhat higher light levels appeared
later in spring as light became more available. This community was dominated by an
important cold water dinoflagellate, Scrippsiella hangoei, which could attain optimal
depth by swimming actively. Adaptation to low light environment and growth near the
ice/water interface could benefit this species at competition later at the onset of the
spring bloom.
OUTI SETÄLÄ
Finnish Environment Institute and Tvärminne Zoological Station
Assessment of the biomass of planktonic ciliates
For the estimation of the amount of pelagic carbon, data on the biomass of planktonic
organisms is required. Until now, the biomass of planktonic ciliates in the Baltic has
been estimated mainly from fixed samples. That leads to biased estimation, because the
most commonly used fixative, acid Lugols´ solution, changes the shape and size of the
cells.
The effect of different concentrations of acid Lugols´ solution on the biomass and cell
numbers of pelagic ciliates was studied during the summers 1998 and 1999. Samples
were taken from several depths at three stations to catch as many different species as
possible. The final concentrations of Lugol in the samples were 0.2, 1, 3, and 5 %. The
concentrations previously used in studies made in Tvärminne, have been <1%, whereas
the concentrations recommended for ocean use are much higher (>5 %). Live samples
were studied immediately after sampling with inverted microscope that was connected
to video camera and computer. The dimensions of the living cells could be measured
from the still images appearing on the computer screen. Cell counts were made with
inverted microscope and an electronic particle counter. The data obtained are still under
analysis.
The occurrence of mixotrophic ciliates and dinoflagellates in Tvärminne area
Mixotrophy, the ability to use alternate nutritional modes, is a common phenomenon in
planktonic ecosystems. Many photosynthetic algae can capture other organisms or
dissolved matter to benefit their nutrition. Also several phagotrophic protists can be
photosynthetic due to symbiotic algae or enslaved, functional chloroplasts. As a result
of the studies on mixotrophy the historical barrier between phyto- and zooplankton
seems to be fading, which makes the understanding of the food web even more
demanding.
Data on mixotrophic ciliates and dinoflagellates were collected throughout the growth
season of 1999 from the open sea station Storfjärden between surface and 10 meters.
Samples were preserved with 20 % buffered formaldehyde (final conc. 2 % formaline),
and were allowed to settle for 12 h in dark. Samples were examined within a week after
sampling with an inverted epifluorescence microscope. In the beginning formaline was
19
used as fixative. Contrary to expectations, the autofluorescence inside fixed cells faded
fast, and several samples were lost. Later on in August the species-rich dinoflagellate
community was fixed with glutaraldehyde (final conc. 1–2 %), which was found to
preserve the cells well and keep the fluorescence vital for a much longer period.
During summer 1999 only few ciliate species were found to be possible candidates to
be mixotrophs. Most of them appeared during the spring bloom (e.g. Bursaria spp.).
Also one small (25-30 µm) unidentified species from the genera Strombidium was
frequently found to possess functional chloroplasts. It is evident that the topic needs
more careful examination, not only by monitoring, but also by experimental studies.
Grazing experiments with Eurytemora affinis adults and nauplii
The aim of this study was to study the grazing effects of adult E. affinis on microprotists, and also to compare the effects of adults and nauplii on the pre-filtered
plankton community. The effects produced by the added nauplii were thought to be
especially interesting, because it has been assumed that the first two naupliar stages do
not feed at all. Two experiments were performed at different phases of the annual
succession (June & July 1999) in order to evaluate the effects of copepod additions on
the microbial community. In the beginning six 2-liter transparent polycarbonate bottles
were filled with seawater filtered through 50 µm plankton net. Two of bottles were
controls; into two adult Eurytemora affinis females were added, and into two small
nauplii (phase I-II) of the same species. Bottles were incubated in situ at 2–3 meters
depth for 48 hours. Samples for nutrient analysis, chl-a and microscopy (bacterioplankton, HNF, phytoplankton, microprotists) were taken prior to the grazer additions
and after 24h and 48h. Preliminary results suggest that the grazing of adult female
copepods was able to decrease the number of ciliates by 30 % in 48 h.
SANNA SOPANEN
Finnish Environment Institute and Tvärminne Zoological Station
Cercopagis pengoi studies – its population dynamic and feeding in Tvärminne area
Cercopagis pengoi, a waterflea native to Ponto-Caspian area, has recently spread to the
Baltic Sea, probably in ballast water of cargo vessels. It was first discovered in 1992 in
the Pärnu Bay and in 1995 it was caught in herring trawls and gill nets in the eastern
parts of the Gulf of Finland. The seasonal cycle of C. pengoi was studied in the
Tvärminne area, SW coast of Finland, during the open water seasons 1998 and 1999.
Samples were taken biweekly from Storfjärden, Längden and Ajax in 1998 and from
Storfjärden and Längden in 1999. Net hauls (100 µm mesh size) from 20 metre to
surface were made at each station, and temperature and salinity were also measured.
Usually Cercopagis appears to the plankton community at the end of June or in the
beginning of July when the water temperature increases above 17 ºC. In 1998
Cercopagis was totally absent in Tvärminne area. This may have been caused by the
low water temperature (under 16 ºC trough the whole summer). In 1999 Cercopagis
appeared to the Tvärminne area at the beginning of July and some specimens were
found still at the beginning of October. However, it seems that Cercopagis is more
abundant at the Eastern part of the Gulf of Finland than in the Tvärminne area where
the water temperature is quite unstable because of repeated upwellings. In areas where
Cercopagis forms regularly mass occurrences, it may cause changes in the food web.
In the pelagic ecosystems, predation often plays a fundamental role in regulating the
diversity and functioning of the whole food web. It is hypothesized that Cercopagis
feeds mainly on smaller sized cladocerans and copepods. To test this hypothesis,
I made preliminary feeding experiments (running for 24 hours) in 1 litre units. Bosmina
longispina maritima or natural mesozooplankton communities were used as a food
20
source. However, no statistically significant changes could been observed. These
results may indicate that Cercopagis is too sensitive for experimental studies.
Hatching success of Cercopagis pengoi resting eggs
Influence of temperature on the hatching of the waterflea, Cercopagis pengoi resting
eggs was studied at Tvärminne Zoological Station in 1998. Five replicate sediment
samples were taken at Tvärminne Storfjärden in the beginning of July and August
using Limnos sediment-sampler. Also salinity and water temperature were measured. A
two centimetre thick slice was cut from the surface of each sediment core and stored at
+3 °C. Altogether 90 eggs were picked from the sediment and incubated at +3, +13 and
+18 °C (30 eggs in each temperature). In the second experiment which started in
August, slightly different incubation temperatures (+5, +10 and +13 °C) were used.
Both experiments lasted for five months.
The results of these experiments showed that the hatching success, as well as the time
of egg development, are strictly dependent on temperature. High temperatures (+18 °C)
seemed to be too high for hatching and even lethal to the eggs. Intermediate temperatures between +5 and +10 °C resulted to best hatching success 63 % and 52 %,
respectively. The time of egg development seemed to be straightly related to increasing
temperature. Predaceous cladoceran, Cercopagis pengoi, appears to be successful in
establishing permanent populations in the Baltic Sea. The production of viable resting
eggs enhances its ability to survive firstly, in the ballast water of cargo vessels and
secondly, in the new areas where environmental factors can be slightly different
compared to its original environment in the Ponto-Caspian area.
MARKKU VIITASALO1,2, RIITTA AUTIO1,2, JONNA ENGSTRÖM1,2, JUHA FLINKMAN1,3, SANDRA
GREEN1,2, TOMI HAKALA2, MIINA KARJALAINEN2, TARJA KATAJISTO1,3, MARJA KOSKI1,2, HARRI
KUOSA3, MIRJA ROSENBERG1,3, MAIJU VIHERLUOTO1,2 AND ILPPO VUORINEN4
1
Tvärminne Zoological Station, 2Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki, 3Finnish Institute of Marine Research and 4Archipelago Research
Institute, University of Turku
Experimental Zooplankton Ecology (The Research Group EZECO)
Crustacean zooplankton have an intermediary position in the pelagic food web. They
consume particulate material formed by phytoplankton, protozoans and metazoans
(diatoms, flagellates, ciliates, rotifers and copepod nauplii), and they serve as food for
higher trophic levels, especially Baltic herring, sprat and mysid shrimps. By combining
experimental work with intensive field studies we aim to determine the role of
crustacean zooplankton in consumption and regeneration of pelagic carbon and its
transfer to pelagic planktivores, and to identify situations where zooplankton fluctuations are regulated by bottom-up processes (food conditions), top-down forces
(predation), or abiotic factors (temperature, salinity and oxygen stress). We concentrate
on aspects that have not previously been studied in the Baltic Sea, such as influence of
food quality to secondary production, recycling of nutrients and organic matter,
interactions between zooplankton and cyanobacteria, as well as behavioural and life
cycle adaptations to predation and unfavourable environmental conditions.
The project is financed by Tvärminne Zoological Station, Walter and Andrée de
Nottbeck Foundation, the Academy of Finland, Maj and Tor Nessling Foundation and
the Finnish Institute of Marine Research. Active cooperation is currently underway
with several institutes and universities in Finland, Denmark, Sweden, Germany and the
Netherlands.
Ph. D. Theses: Nos. 1061, 1213 and 1230.
21
MARJA KOSKI1, 2, HARRI KUOSA3, SARI PERTOLA2 AND MARKKU VIITASALO1, 2
1
Tvärminne Zoological Station, 2Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki and 3Finnish Institute of Marine Research
Effects of water temperature, food concentration and food quality to copepod
growth and production (EZECO project 1)
We investigated the effects of environmental factors, such as temperature, food quantity and food quality on feeding and production of calanoid copepods, using both
laboratory experiments and field sampling. All these factors were found to affect
copepod production, either directly, or indirectly through their effects on body size or
feeding of copepods. For example, there was a direct positive relationship between
copepod egg production and water temperature, whereas the indirect effect through
diminishing body size was negative. In contrast, both copepod egg production and
body size increased with increasing chlorophyll-a concentration, which indicated that
food concentration (and not temperature) is the dominating factor affecting copepod
production. However, copepods responded differently to different food species. While
with some algae copepod growth was rapid (e.g. Rhodomonas sp., Thalassiosira
weissflogii, Gymnodinium simplex), with other species copepods did not develop or
reproduce at all, even at high food concentration (e.g. Amphidinium sp., Dunaliella sp.,
Chrysochromulina polylepis, N-limited T. weissflogii). The differences in food quality
of algae were probably either due to nitrogen limitation or lack of biochemical
compounds necessary for growth. Further, different development stages of copepods
responded differently; egg production demanded higher quality food than somatic
growth, which in turn demanded higher quality food than mere survival. In general,
Baltic Sea copepods seem to be limited by both food quantity and quality, especially
during the summer when the amount of phytoplankton is low and the phytoplankton
community is dominated by green algae and cyanobacteria.
Publications: Nos. 1108, 1212, 1220, 1231 and
1. Koski, M., Klein Breteler, W. & Schogt, N. 1998: Effect of food quality on rate of
growth and development of the pelagic copepod Pseudocalanus elongatus
(Copepoda, Calanoida). – Marine Ecology Progress Series 170: 169–187.
MARJA KOSKI1,2, JONNA ENGSTRÖM1,2, MARJAANA KOKKONEN2, SARI REPKA4, MARKO REINI1
1,3
5
4
1
KAINEN , MIRJA ROSENBERG , KATRIN SCHMIDT , KAARINA SIVONEN , ULLA SJÖLUND , AND
1,2
MARKKU VIITASALO
1
Tvärminne Zoological Station, 2Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki, 3Finnish Institute of Marine Research, 4Department of Applied
Chemistry and Microbiology, University of Helsinki and 5Institute of Baltic Sea Research,
Warnemünde, Germany
The interaction between harmful algae and zooplankton (EZECO project 2)
1. Do toxic algae have beneficial effects on copepod production? It has been
proposed that the effect of ‘harmful’ algae on zooplankton may be different when fed
alone and when fed in mixtures with other ‘good’ quality food. In 1997 we tested this
hypothesis by feeding the potentially toxic prymnesiophyte Prymnesium patelliferum to
the calanoid copepod Eurytemora affinis. Egg production and egestion were low and
mortality high in the presence of sole P. patelliferum. However, when P. patelliferum
was added to a diet of the green alga Brachiomonas submarina or the crysophycean
Pseudopedinella elastica, egg production was higher than with these algae alone. This
suggests that P. patelliferum contains some compounds that are absent from green
algae and chrysophyceans.
22
2. How do cyanobacteria affect survival, grazing and reproduction of Baltic
copepods? In 1998 we investigated the effects of the cyanobacteria Nodularia sp. and
Aphanizomenon flos-aquae to the feeding and reproduction of the copepods
Eurytemora affinis and Acartia bifilosa. E. affinis fed actively on a non-toxic strain of
Nodularia sp. and to some extent on a toxic strain, whereas A. bifilosa totally avoided
both strains. However, although E. affinis females could feed and survive on
cyanobacteria, their egg production and the hatching success of eggs were very low
(even deformed egg sacs were observed). The results suggest that, in contrast to
Prymnesium patelliferum (see above), Nodularia sp. lack biochemical compounds
necessary for copepod reproduction. Therefore, copepod species able to avoid feeding
on the toxic algae may be favoured during cyanobacteria mass-occurrences, at least if
alternative food is available amongst the bloom.
3. The effect of a decaying cyanobacteria bloom on the pelagic ecosystem. We
hypothesised that an ageing cyanobacteria bloom will be colonised with bacteria and
ciliates, which will provide food for mesozooplankton. In July 1999, we made a
mesocosm study where cultured Nodularia sp. were added into 150-l enclosures filled
with 100-µm-filtered seawater. A cyanobacteria bloom developed and, during the next
15 days, the enclosures were regularly sampled for nutrients, chlorophyll-a
concentration, phytoplankton and ciliate species composition and bacteria abundance,
as well as phytoplankton pigments, proteins, fatty acids and cyanobacteria toxins. To
determine the response of zooplankton to changes in the food quality of the bloom, we
made weekly experiments where mesocosm water was provided to Acartia bifilosa and
Eurytemora affinis. Despite a high concentration of toxins (7-14 µg nodularin l-1), E.
affinis, Synchaeta sp. and Bosmina longispina survived in the mesocosms. In the
feeding experiments, copepod mortality was low and egg production equal or higher
than in controls with ‘good food’ (Brachiomonas submarina). The results thus suggest
that mesozooplankton species are able to survive and reproduce within an ageing
cyanobacteria bloom. If this was based on feeding on the decaying cyanobacteria
filaments, or to utilisation of flagellates and ciliates that proliferated amongst the
bloom, will be revealed when all the data from feeding experiments and mesocosm
monitoring will be analysed.
Publications: No. 1232 and
1. Koski, M., Rosenberg, M., Viitasalo, M., Tanskanen, S. & Sjölund, U. 1999: Is
Prymnesium patelliferum toxic for copepods? Grazing, egg production and egestion
of the calanoid copepod Eurytemora affinis in mixtures of ‘good’ and ‘bad’ food. –
ICES Journal of Marine Science 56 (in press).
2. Engström, J., Koski, M., Viitasalo, M., Reinikainen, M., Repka, S. & Sivonen, K.:
Feeding interactions of Eurytemora affinis and Acartia bifilosa with toxic and nontoxic Nodularia sp. – Submitted manuscript.
RIITTA AUTIO1, 2, SANNA TANSKANEN1 AND MARKKU VIITASALO1, 2
1
Tvärminne Zoological Station and 2Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki
The interaction between zooplankton and bacteria (EZECO project 3)
1. Zooplankton activity providing dissolved organic carbon for bacterioplankton
growth. Batch culture experiments were run between May and August 1997 to study
the importance of zooplankton grazing in fuelling the microbial loop. Green algae
(Brachiomonas submarina) were fed to the copepod Eurytemora affinis in continuous
(0.8 µm filtered water) and preincubated (0.2 µm screening, 20 % addition of natural
brackish water bacteria) units for 3 days. Bacterial biomass and production and the
23
growth of heterotrophic nanoflagellates were assessed. In May, June and August
zooplankton grazing released enough carbon to double the bacterial growth. In July this
effect was only marginal, probably due to a heavy cyanobacteria bloom releasing
plenty of UDOC. The results thus indicate that zooplankton activity is able to fuel the
microbial loop, but only if the bacterial community is carbon limited.
2. The response of bacterioplankton to various sources of carbon. In 1999 the
response of free-living planktonic bacteria to various carbon sources was studied. The
experimental units covered the algal (Brachiomonas submarina, 35–50 µg chl-a l-1),
zooplanktonic (adult female Eurytemora affinis, 60-80 ind. l-1) and ‘sloppy feeding’
pathways of carbon release. Pure cyanobacterial bloom water was also used and the
potential of the bacteria to respond to an extracellular carbon source (sucrose) was
assessed. Thymidine incorporation rate and the increase of bacterial abundance were
determined. The preliminary results indicate that the bacterial community was carbon
limited and that the growth rates were highest in the units with zooplanktonic
influence. Also, algal presence significantly increased bacterial productivity, whereas
the effect of sloppy feeding was negligible.
MIRJA ROSENBERG1, 2, ANNA-STIINA HEISKANEN3, MARJA KOSKI1, 4 AND MARKKU VIITASALO1, 4
1
Tvärminne Zoological Station, 2Finnish Institute of Marine Research, 3Finnish Environmental
Institute and 4Department of Ecology and Systematics, Division of Hydrobiology
The fate of copepod fecal pellets in Tvärminne archipelago (EZECO project 4)
Sediment traps were used to investigate the sedimentation of copepod faecal pellets in
three areas in the Tvärminne and Ekenäs archipelagos, representing a sheltered bay
(Sällvik), an archipelago area (Storfjärden) and the open sea (Längden–Storgadden).
Faecal carbon sedimentation was always less than 0.05 % of the total sedimentation of
particulate organic carbon, whereas the faecal carbon production (estimated from copepod abundance) contributed to 4–17 % of particulate organic carbon sedimentation.
This indicates that >99 % of the faecal material was remineralised within the mixed
water layer. However, in the area and season dominated by the large sized calanoid
copepod Limnocalanus macrurus (Sällvik in spring), faecal carbon sedimentation was
an order of magnitude higher than at the other two stations. From June onwards, when
Sällvik was dominated by cyclopoids, the situation reversed: the faecal carbon sedimentation remained 30 % lower than in the archipelago. We suggest that the overall
contribution of copepod faeces to vertical carbon export in the northern Baltic Sea is
small, but that seasonal and spatial variations in hydrography and mesozooplankton
species composition significantly affect the faecal carbon sedimentation rates.
Publication: No. 1221.
JUHA FLINKMAN1,2, EERO ARO3, SANDRA GREEN1, 4, TOMI HAKALA4, MIINA KARJALAINEN4, MAIJU
VIHERLUOTO1, 4, MARKKU VIITASALO1, 4 AND ILPPO VUORINEN5
1
Tvärminne Zoological Station, 2Finnish Institute of Marine Research, 3Finnish Game and
Fisheries Research Institute, 4Department of Ecology and Systematics, Division of Hydrobiology,
University of Helsinki and 5Archipelago Research Institute, University of Turku
Interactions between zooplankton and their predators (EZECO project 5)
1. Copepod life cycle strategies in fish predation avoidance. Baltic herring prey
selectively on egg-carrying zooplankton. Recently, it has been shown that copepod
eggs may survive the passage through fish intestines. We provided egg-carrying
copepod females to adult herring in aquaria and determined the hatching rate of eggs
extracted from faeces. 82 % of the eggs hatched during 48 h, which indicates no
24
significant decline in hatching rate during gut passage. The membrane of the faecal
capsule was easily broken up, thus facilitating the release of eggs from the pellets.
Some nauplii hatched already within the faeces and will therefore be quickly released
into the water; others will inevitably sink onto the bottom, where the hatching of eggs
will be delayed. We suggest that the survival of E. affinis eggs in herring guts increases
the spatial and temporal dispersion of the reproductive output in this copepod species.
2. Copepod escape reactions: behavioural adaptations to predation. We video
filmed the copepods escaping from three-spined sticklebacks and mysid shrimps
(Neomysis integer). The copepods detected the mysids from a significantly longer
distance than they detected the smoothly swimming sticklebacks. Consequently, the
capture success of the sticklebacks was higher than that of mysids. A hydrodynamic
model accurately predicted the positive relationship between the stickleback approaching speed and copepod reaction distance. In contrast, the model did not conform with
observations on mysids, which suggests that the strength of the hydrodynamic signal
created by a mysid is not related to its swimming speed. Further, we assessed the
sensitivity of the 2 prey species to hydrodynamic disturbance against an artificially
created water flow. The water flow speed eliciting an escape response in Temora
longicornis was 4 times higher than that in E. affinis, which explains why T. longicornis was clearly easier prey to sticklebacks than E. affinis.
3. Comparison of prey selectivity in herring and mysids. We obtained prey
selectivity indices for 2 Baltic Sea predators, herring (Clupea harengus membras L.)
and Mysis mixta, from studies made either in the field or in the laboratory. The herring
behaved as size-selective predators, whereas prey selection in M. mixta was not based
on size. However, certain similarities were detected, especially in case of copepod prey.
This suggests that similar processes determine the vulnerability of copepods to
predation by both herring and mysids, whereas this is not the case for cladocerans.
Comparing these results with the prey escape capabilities assessed with the siphon flow
allowed us to identify cases where the predators showed ‘true’ positive selection (i.e.
preyed on difficult prey, such as Eurytemora affinis), and where the selection was
‘truly’ negative (i.e. ignored easy prey such as Pseudocalanus elongatus). The results
also suggest that Temora longicornis and E. affinis face a more intense predation
pressure than Acartia spp., P. elongatus and Bosmina longispina maritima.
4. Effects of environmental factors and cyanobacteria on the feeding and growth
of fish larvae and juveniles. For fish larvae, the prey detection distance is one of the
most important factors affecting their feeding success, because it directly affects the
volume of water the fish can scan for food. In 1999 we made preliminary experiments
(with video methods) to find out if cyanobacteria colonies interfere with prey detection
and feeding success of juvenile sticklebacks. We will proceed to analyse how the prey
detection distance varies with different prey species and in different environmental
conditions (e.g. light conditions, water transparency). These experimental results will
be used to calculate the realised encounter rates between fish larvae and different prey
types, and will help to interpret results from analysing an extensive field data on herring larval growth, obtained from the Finnish Game and Fisheries Research Institute.
Publications: Nos. 1186, 1204 and
1. Viitasalo, M., Flinkman, J. & Viherluoto, M.: Zooplanktivory in the Baltic Sea: a
comparison of prey selectivity by Clupea harengus and Mysis mixta. – Submitted
manuscript.
2. Flinkman, J. & Viitasalo, M.: Survival of Eurytemora affinis eggs through Baltic
herring digestive tract: a bet-hedging strategy increasing spatial and temporal
dispersion of nauplii? – Submitted manuscript.
25
MAIJU VIHERLUOTO1,2, JONNA ENGSTRÖM1,2, JUHA FLINKMAN1,3, HARRI KUOSA3, MILLA RAUTIO1,2
1,2
AND MARKKU VIITASALO
1
Tvärminne Zoological Station, 2Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki and 3Finnish Institute of Marine Research
Mysid feeding studies (EZECO project 6)
Mysid shrimps are important omnivores that feed on various food types from detritus
and phytoplankton to larger crustacean zooplankters. However, not much is known
about their prey selection or seasonal changes in their feeding habits. We studied the
growth, feeding and food selection of the most abundant pelagic mysid species, Mysis
mixta and M. relicta, at an open sea location off the Tvärminne archipelago.
According to a stomach analysis done in 1997, the small mysids (ca 5 mm long) fed on
sedimented phytoplankton in the early summer but shifted gradually to a more
carnivorous diet along with growth. The diets of the two mysid species were 75 %
overlapping, M. mixta being more carnivorous. An increase in the growth rates of M.
mixta was observed when the share of copepods in the diet increased. This suggests
that food quality and taxonomy influence the growth of pelagic mysids in the northern
Baltic.
In 1998 we studied the functional responses and prey selection of M. mixta with natural
prey assemblages in laboratory. Variation in prey preference was high, but generally
copepods were selected over cladocerans. The importance of the prey groups also
changed along with mysid growth. The food saturation level was reached at ~500
µgC l-1, which implies that in nature the feeding of M. mixta rarely saturates, and that
mysids have to feed on patches of zooplankton and phytoplankton to get enough food.
In another experimental study done in 1997, the littoral mysid Praunus flexuosus fed
intensively on cladocerans, and suppressed their predation on copepods when cladocerans were offered as alternative food. We suggest that P. flexuosus capture cladocerans by creating a suspension feeding current, whereas the evasive copepods need to
be perceived and attacked individually. Probably, for littoral mysids that remain in the
vicinity of macroalgae for most of the day, the stationary suspension feeding mode is
relatively more advantageous than the raptorial mode because they have less possibilities for searching for food than the ‘cruising’ open sea mysids.
Furthermore, in 1999 we investigated the effect of light level and cyanobacteria on the
feeding rate of both pelagic and littoral mysids. Preliminary results show that light
affects more pelagic species, and that feeding is more effective in total darkness than in
light. Further, mysids seem to be able to feed on cyanobacteria, but have a tendency to
avoid toxic Nodularia sp. filaments.
Publications: No. 1203 and
1. Viitasalo, M. & Rautio, M. 1998: Zooplanktivory by Praunus flexuosus (Crustacea:
Mysidacea): functional responses and prey selection in relation to prey escape
responses. – Marine Ecology Progress Series 174: 77–87.
2. Viherluoto, M., Kuosa, H., Flinkman, J. & Viitasalo, M.: Food utilisation of pelagic
mysids Mysis mixta and M. relicta in the northern Baltic Sea. – Submitted
manuscript.
3. Viherluoto, M., Viitasalo, M. & Kuosa, H.: Growth rate variation in the pelagic
mysid, Mysis mixta (Mysidacea): effect of food quality? – Submitted manuscript.
26
TARJA KATAJISTO1,2 AND MARKKU VIITASALO1,3
1
Tvärminne Zoological Station, 2Finnish Institute of Marine Research and 3Department of Ecology
and Systematics, Division of Hydrobiology, University of Helsinki
Zooplankton life cycles in the northern Baltic: effects of temperature and anoxia
on copepod resting eggs (EZECO project 7)
We have studied benthic resting eggs in the life cycles of the three dominant calanoid
copepods (Eurytemora affinis, Acartia bifilosa and A. tonsa) in the Tvärminne area. In
addition to determining hatching success of eggs extracted from the sediments, we have
studied the effect of temperature and oxygen conditions on the development of eggs
produced by females in the laboratory.
Eggs laid by E. affinis females in summer hatched in 2 days at 13 °C and in 15 days at
1–3 °C. In the autumn, eggs remained dormant for 2–5 months at 2–3 °C. Eggs that
were extracted from the sediment surface showed a similar development as the eggs
derived from females. In contrast, eggs from deeper sediment layers had probably
concluded their refractory period, as they hatched within 2 weeks. For E. affinis,
production of benthic eggs thus serves as an over wintering strategy as well as a means
for long-term survival.
A. bifilosa eggs developed in 2 to 16 days (in 18 and 1.5 °C, respectively) regardless of
season, and entered dormancy only if subjected to anoxic conditions. We suggest that,
in shallow coastal areas of the northern Baltic, A. bifilosa eggs often sink onto the
bottom before hatching and continue development if not buried under the sediment.
Thus, eggs are deposited onto the bottom throughout the productive period and hatching occurs to some extent around the year.
The warm water species A. tonsa has recently become abundant in the Tvärminne area.
In hatching experiments done in late summer and autumn, egg development varied
according to water temperature and incubation month, as well as between clutches. In
August, eggs entered dormancy at <3 °C, hatched gradually (during 4 months) at 6 °C,
and hatched ‘immediately’ (in 2 to 3 days) at 13–18 °C. The viability of eggs in the
sediments declined during the winter, being >80 % in November and <40 % in spring.
Since A. tonsa dwells in plankton only in late summer, eggs that retain their viability in
the sediment for several months are essential for the survival of this species in the
northern Baltic.
The potential of A. bifilosa and A. tonsa eggs to withstand anoxia was assessed by incubating eggs in anoxic water. The eggs stayed viable for several months, which confirms
the potential for recruitment into plankton in a seasonal scale. E. affinis eggs extracted
from old anoxic sediments, showed high hatching success (even 100 % in 5 year old
sediments). Thus, although anoxia is harmful for the recruitment of nauplii into the
plankton, it may also benefit the species by lengthening the time that eggs can stay
viable in the sediment.
Publications: Nos. 1063, 1115 and 1185.
27
2.3. BENTHIC STUDIES
JOUNI LEHTORANTA AND ANNA-STIINA HEISKANEN
Finnish Environment Institute, Impacts Research Division
Internal nutrient loading and sedimentation in the coastal Gulf of Finland, Baltic
Sea
The study aims to estimate the magnitude of internal nutrient loading from sediments in
relation to total downward flux at the coastal Gulf of Finland. We have measured seasonal nutrient fluxes from the sediments of an oxic and anoxic accumulation bottoms in
combination with sedimentation measurements using sediment traps. The annual net
sedimentation can be used to approximate the share of pelagic primary production
based on nutrients derived outside from the pelagic system (i.e. winter mineralised
nutrients, nutrients transported by vertical mixing and upwelling from deep waters,
terrestrial and atmospheric loading). Thus our aim is to estimate how much of the total
external nutrient supply to the pelagic system is potentially based on nutrient regeneration from the sediments during the annual cycle.
The sampling areas are located at the accumulation bottoms at the close vicinity of the
Tvärminne Zoological Station. The two sampling sites represent a well oxygenated
area in the archipelago (Tvärminne Storfjärden) and an area where periodical oxygen
deficiency in near-bottom water occurs (Storgadden sediment basin). The total amount
of net measured using automated sediment traps moored below the photic zone.
Particulate and total nutrients (C, N, P) of the settled material are also measured. The
sediment samples are taken 10 times during one seasonal cycle at each station. The
sediment cores (3–4 replicates) are incubated at in situ temperature in tubes equipped
with magnetic stirring and water circulation. The flux rates of dissolved reactive phosphorus (DRP), total phosphorus (TDP) nitrate (NO), nitrite (NO2-), ammonium (NH),
total nitrogen (TDN), total dissolved iron (TDFe) and silica (DSiO) are measured.
The peak sedimentation of spring bloom occurred early in 1999. The sedimentation of
organic matter was highest in early May at Storgadden and declined immediately
thereafter to the low summer levels (from 120 to 20 mg C m-2 d-1). The C:N ratios were
low (3 to 5 by weight) and N:P and C:P ratios high (60–95 and 200–270 by weight,
respectively) reflecting the bioorganic origin of settling material during spring, while in
summer the decrease in C:P and N:P ratios suggested dominance of resuspended
material in the trap catch. Pore water DRP, TDP, NH, TDN and DsiO were high in the
0–0.5 cm layer indicating diffusive flux of these dissolved substances to the overlying
water, especially at Storgadden. In deeper sediment layers (5 to 10 cm) pore water
concentrations of DRP, TDP, NH, TDN and DsiO were high (several milligrams per
liter). Benthic fluxes of DRP, TDP, NH, TDN and DsiO from sediment to water increased from spring to summer and the highest fluxes were measured in July. Benthic
fluxes were low in autumn and especially during winter.
Publications: Nos. 1183, 1190, 1233 and
1. Lehtoranta, J. Pitkänen, H. & Sandman, O. 1997: Sediment accumulation of
nutrients (N, P) in the eastern Gulf of Finland (Baltic Sea). – Water, Air and Soil
Pollution 99: 447–486.
2. Lehtoranta, J. 1998: Net sedimentation and sediment–water nutrient fluxes in the
eastern Gulf of Finland (Baltic Sea). – Vie Milieu 48(4): 341–352.
28
MAGNUS LINDSTRÖM
Tvärminne Zoological Station and Walter and Andrée de Nottbeck Foundation
Effect of macroinvertebrate bioturbation on sediment oxygenation
The bioturbation effects of the crustaceans Monoporeia affinis, Mysis relicta and the
clam Macoma balthica have bee investigated in aquaria using infrared video technique.
The amphipod M. affinis burrows into the sediment several times a night, thereby
redistributing sediment and exposing it to oxygen in the overlying water. M. balthica
burrows down into the sediment and more or less ceases to move around. During its
filter feeding it searches the sediment surface with its inhaling siphon and replaces
undigested materia by exhaling. It deposits its faeces in clearly identifiable patches.
The mysid M. relicta mixes the sediment with its swimming legs while walking on the
bottom. These three ways of behaviour affect the sediment surface in different ways.
The vertical transport of solutes and gases is enhanced by these activities, and when
burrows are present the surface area is also enlarged. An attempt has been made to
quantify the effects of animal behaviour on this process. I use infrared video recording
for recording the animals’ behaviour and for measuring the increase of the oxygenised
layer, which is manifested by the light brown colour of oxidized iron. In specially
designed experiments sediment is sliced vertically to reveal burrows for calculation of
their surface areas. The next step will include measuring the pH, redox potential and
oxygen profile in high resolution for estimation of the sediment’s chemical capacity.
An enlarged project including nutrient binding and release is being planned.
2.4. PHYSICAL ENVIRONMENT
TAPANI STIPA
Department of Geophysics, University of Helsinki
Studies of diapycnal mixing in the Baltic Sea
In an earlier study, it was discovered that diapycnal mixing in a coastal estuary
(Pohja/Pojo Bay) was difficult to parameterise as directly proportional to the Brunt–
Väisälä frequency. Moreover, the diapycnal eddy diffusivity was found to be different
for heat and salt. An enhanced understanding of these discrepancies is sought within
the DIAMIX-project, studying diapycnal mixing in the Baltic Proper. Measurements
with a towed undulating CTD from Tvärminne Zoological Station, but deployed on the
Gothenburg University Research vessel Skagerak in June, 1997, revealed the presence
of non-hydrostatic internal waves near the halocline, with an amplitude of several
meters. The finding was later confirmed by moored instruments (H. U. Lass, pers.
comm.). These waves are near the dissipation range and thus can be expected to take
part in the effective mixing. In a later expedition, in 1.–11.3. 1999, the profiling current
meter of Tvärminne, situated on a stationary R/V Aranda in the Gotland deep, revealed
a passing halocline eddy that had a large shear associated with it. While the data
analysis is still underway, it seems safe to say that the halocline is by no means a
stagnant layer, but rather a dynamic interface whose properties are determined by
processes that we may not entirely understand at the time of writing. Progress towards
a new consensus is possible by a co-operation between project participants from other
parts of the Baltic.
Publication: No.1110.
29
SEPPO KAITALA
Deartmenpt of Ecology and Systematics, Division of Environmental Biology, University of Helsinki
Modelling watershed area of the River Mustionjoki by GIS
The River Mustionjoki has a watershed area of ca. 2000 km2. It outlets to the fjord-like
Pojo Bay, which has for decades been intensively studied because of its very special
hydrographic and biological characters. This study aims to model the Watershed area
of the river using Geographic Resources Analysis and Support System (GRASS) and
Geographic Information System (GIS). The watershed area location was obtained as
ArcView shape files with subbasin delineation of the 1st, 2nd and 3rd orders. Also with
GRASS raster modelling command r.watershed several orders of sub-basins were
subtracted from the Global 30 Arc Second Elevation Data Set (Gtopo30) raster model
(data from US geological Survey). The bathymetrical point data of the bay, obtained by
Multi-mode Sonar System (MD DSS), was constructed as a 3-D model. The depth was
measured with the accuracy of 50 mm. Contours of every 500 mm were used to model
the bottom surface of the bay. The GIS model of the watershed area is intended to be
used in further work to evaluate inorganic nutrient pool and nutrient flow from
different parts of the watershed subbasins to Pojo Bay.
ANTTI LINDFORS
Department of Geophysics, University of Helsinki
Use of satellite images to study coastal dynamic features
Radar is an active instrument, which transmits electromagnetic radiation and measures
the reflected pulse from the surface. By radar the roughness of the surface can be
obtained along with some other parameter. Most of the dynamical features, even those
appearing in deeper layers of the sea, have some effects on the surface. This could be
for example algae or other surface active material floating on the sea surface. All of
these features have different backscattering coefficients, which makes them visible in
radar images. This information combined with sea truth data gives a powerful tool for
distinguishing and understanding different events and phenomena in the coastal region.
The aim for this work was to see if satellite imagery would provide more additional
information about coastal dynamic phenomena. During the summer 1998, we collected
CTD (Conductivity-Temperature-Depth) and ADCP (Acoustic-Doppler-CurrentProfiler) data from western Gulf of Finland. The results were plotted and compared
with ERS-2 (European Remote Sensing Satellite-2) SAR (synthetic Aperture Radar)
data.
The most typical coastal zone structures in our radar images were different natural
slicks and eddy-like patterns. Dimensions varied from 1.5 to 40 km for eddies, which
means that they affect very strongly the whole current field in the Gulf of Finland.
Algal blooms, rain cells and turbulence caused by ships are rather easy to recognize,
but especially more detailed information about algal blooms always needs in situ
measurements.
The biggest problem with using remote sensing tools is the fact that they see only a thin
layer of sea. This means that some of the deep sea phenomena become unreachable.
The other limiting factor is the surface wind; especially during stronger winds the
surface becomes too coarse for backscattering and all the details disappear.
30
NOBUYOSHI ISHIKAWA1, TOSHIYUKI KAWAMURA1, MATTI LEPPÄRANTA2, ANTTI LINDFORS2, KAI
RASMUS2, KUNIO SHIRASAWA3 AND ATSUSHI TAKIZAWA4
1
Institute of Low Temperature Science, Hokkaido University, Japan, 2Department of Geophysics,
University of Helsinki, 3Sea Ice Research Laboratory, Institute of Low Temperature Science, and
4
Graduate School of Environmental Earth Science, Hokkaido University, Japan
Sea Ice Experiment Hanko-99
Sea ice occurs annually in the Gulf of Finland for 4–5 months. In mild winters only the
eastern part freezes but normally the basin becomes fully ice covered. The maximum
annual thickness of coastal fast ice is 30–80 cm. The brackish water ice of the Gulf of
Finland has a fine scale structure similar to sea ice as normally is the case when the
water salinity is more than 1 ppt. The ice crystals have irregular boundaries and the
brine entrapment is significant the salinity of the ice being 0.5–2 ppt. Of the ice
formation mechanisms, the congelation ice growth appears to be dominant. Snow ice
amounts to 10–30 % of the whole ice sheet, and the frazil ice proportion is small.
Finnish-Japanese cooperative research programme "Ice climatology of Okhotsk and
Baltic Seas" was initiated in 1995. This programme examines (1) Long-term variability
of ice seasons, (2) Ice melting process, and (3) Sea ice remote sensing in these two
seas. The work first progressed through mutual visits in the research laboratories and
joint data analyses. In 1999 joint field programmes were commenced in both seas; in
the Baltic Sea, the research area was the Hanko peninsula region at the mouth of the
Gulf of Finland. The ice season of 1999 was close to normal.
The Baltic experiment, named as Hanko-99, was based in the Tvärminne Zoological
Station of the University of Helsinki. Tvärminne and Santala Bay were the main sites.
The investigations focused on the structure and properties of the Baltic brackish ice,
heat budget, and solar radiation. Ice sampling extended further inland to catch the
transition from sea ice to fresh water ice in the ice structure. The study region covers
the waters at the Hanko Peninsula from Tvärminne to Tammisaari town and further
into the Pojo Bay. This region is particularly interesting for brackish water ice studies
since the salinity of the water decreases there from 6 ppt down to nearly zero. The sea
area in the study region is mainly shallow and the fast ice boundary goes normally at its
outer southern shore.
The experiment Hanko-99 took place during the whole ice season 1999 for the seasonal
data collection, and an intensive study phase was performed during 10–21 March 1999.
The seasonal study was commenced on 20 January and lasted three and half months.
The data collection was successful. The data are used for the basic research of brackish
ice and for mathematical modelling of sea ice thermodynamics.
31
3. POPULATION BIOLOGY
V. ILMARI PAJUNEN1 AND IRMELI PAJUNEN2
1
Department of Ecology and Systematics, Division of Population Biology and, 2Department of
Animal Science, University of Helsinki
Dispersal in rock pool Corixids: the influence of population density and food
Field experiments in rock-pools from which corixid larvae were removed have been
continued. The details of experimental design were described in Tvärminne Studies 6.
The combined three-year material now allows more precise estimation of dispersal. In
experimental rock-pools the average daily elimination of adults was 0.183 + 0.017 for
Arctocorisa carinata and 0.271 + 0.020 for Callicorixa producta. In controls having
normal larval corixid populations the values were 0.150 + 0.017 and 0.181 + 0.015,
respectively. The difference is statistically highly significant for C. producta. A
regression analysis suggested that the difference between experimental and control
populations increased with increasing overall elimination. During dispersive flights
adults seem to sample successive rock-pools and continue flight when arriving a high
density patch.
MIKAEL KILPI1, TUULA HOLLMÉN2, MARTTI HARIO3, J. CHRISTIAN FRANSON4 AND MARKUS ÖST1
1
Tvärminne Zoological Station and Department of Ecology and Systematics, Zoological
Laboratory, University of Helsinki, 2Department of Basic Veterinary Medicine, University of
Helsinki, 3Finnish Game and Fisheries Research Institute, 4National Wildlife Health Center, U.S.
Geological Survey, Madison
Population dynamics of eider ducks (Somateria mollissima) in the Northern Baltic:
a broad approach
The common eider is the most common species of diving duck in the Baltic Sea. In the
Gulf of Finland, the species has declined substantially in some areas. Duckling
production in declining populations has been very low (1–5 % fledge), and duckling
production in other areas varies dramatically between years. Mass-death events have
also affected adult birds. We started a project to unravel the background for the decline
and the mass-deaths in 1996 covering both the Gulf of Finland and the Archipelago
Sea. We studied background contamination (lead, trace elements and PCBs), occurrence of infectious diseases (bacterial, viral and fungal) and the state of the staple food
resources (blue mussels, Mytilus edulis). Background levels of contaminants were
generally low, but some effects of lead can be found. Infectious diseases affect both
ducklings (a total die-off in the entire area in 1996) as well as adults (a massive death
event among males in 1998). So far we have found at least three viral agents involved
in mass-death. In the eastern part of the Gulf of Finland, blue mussel populations in
1996–98 were depressed to a level likely explaining the low production of fledglings.
Publication: No. 1200 and
1. Hario, M., Hollmén, T., Kilpi, M., Lehtonen, J.T., Mustonen, O., Westerbom, M. &
Öst, M. 1999: Riittääkö haahkalle ravintoa Suomenlahdella? (Summary: Are northern Baltic eiders food-limited?) – Suomen Riista 45: 34–43.
2. Franson, J. C., Hollmén, T., Poppenga, R. H., Hario, M., Kilpi, M. & Smith, M.
2000: Selected trace elements and organochlorines: some findings in blood and eggs
of nesting common eiders (Somateria mollissima) from Finland. – Env. Toxicology
and Chem. 19: 1340–1347.
3. Hollmén, T., Franson, J. C., Docherty, D. E., Kilpi, M., Hario, M., Creekmore, L. H.
& Peterson, M. P. 2000: Infectious bursal disease virus antibodies in eider ducks and
herring gulls. – Condor 102: 688–691.
32
MIKAEL KILPI
Tvärminne Zoological Station and Department of Ecology and Systematics, Zoological Laboratory,
University of Helsinki
Colonial breeding in herring gulls (Larus argentatus)
I started a study on colonial herring gulls in Tvärminne in 1990. The aim of the study
was to explore the pros and cons of colonial breeding in this large-bodied gull species.
The study involved monitoring of parental behaviour and chick survival in varying
conditions. The colony declined from 140 pairs (in 1990) to 75 pairs (in 2000). The
decline was likely due to changes in the feeding regime in the area, as it also involved a
substantial decrease in fledgling production. The density of the breeders consequently
dropped as the colony declined, as did the proportion of prospectors present in the
colony. The study in its present form will be terminated in 2000.
Publications: No. 1181 and
1. Hillström, L., Kilpi, M. & Lindström, K. 2000: Is asynchronous hatching adaptive in
herring gulls? – Behav. Ecol. Sociobiol. 47: 304–311.
OLLI HALKKA, LIISA HALKKA AND KAISA ROUKKA
Division of Genetics, Department of Biosciences, and Tvärminne Zoological Station, University of
Helsinki
Genotype-environment interaction in Philaenus spumarius populations
Genotype-environment interaction, or GEI, is difficult to demonstrate in natural populations. Whenever different genotypes favour dissimilar environments, each of the
genotypes has an unique fitness profile.
In the Tvärminne archipelago, the polyphagous meadow spittlebug (Philaenus
spumarius) can show dissimilar frequencies of alleles of a colour polymorphism gene
locus in populations living in adjacent meadows which have dissimilar food plant
coverages. This situation indicates that GEI may be present. One of the possible GEI
mechanisms could be dissimilar food plant preferences among the colour morphs.
Nymphs in cages on different food plants showed their colour phenotypes after emergence into adults. To ascertain that selection is operating, it was necessary to show that
migration is not a powerful factor in the life of the spittlebug populations (see
Tvärminne Studies, this issue).
Moreover, it was necessary to study food plant choice of colour morphs under
conditions in which many generations of large populations lived in mixed stands of
food plants within about 10 square metres. Follow-up over many generations removed
the possibility that historical founder effects or intermittent genetic drift were
influential.
Under such critical conditions, it was possible to show that the colour morph lateralis
(genotype pt/pL) favours significantly (at the P < 0.01 level) the food plant Filipendula
ulmaria. This food plant is a safe feeding site in normal years, but is very risky in dry
years. This means that pt/pL has a fitness profile which varies in a unique way.
33
OLLI HALKKA, LIISA HALKKA AND KAISA ROUKKA
Division of Genetics, Department of Biosciences, and Tvärminne Zoological Station, University of
Helsinki
Selection, migration and genetic drift in spittlebug populations
The Tvärminne island populations of the univoltine spittlebug Philaenus spumarius
(Homoptera) often experience great losses during the first two or three nymphal instars.
Mortality of the nymphs is variably dependent on the food plants in climatically
dissimilar years. The size of most of the investigated nymph populations is in most
years larger than 1000, and random processes can change gene frequencies of a colour
polymorphism significantly only during climatic catastrophes. In adult populations,
random drift operates in bottleneck generations. Caged nymphs and sweep net samples
of adult populations were studied.
Migration of adults between populations living in different meadows of an island is not
intensive enough to be able to change meadow-specific allele frequencies. This was
found in studies on changes of frequencies of colour polymorphism gene alleles in 24
generations. Selection at the nymph stage overcomes the effects of migration of adults.
The three evolutionary forces, selection, random processes and migration operate
differentially in the often quite large nymph populations and the occasionally very
small adult populations. In the literature, not much attention has been paid to the
possibility that different stages of the life cycle are dissimilarly affected by evolutionary forces.
TOMAS ROSLIN
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
Spatial ecology of dung beetles in the genus Aphodius
Related species utilising similar resources are often assumed to show similar spatial
population structures and dynamics, but empirical evidence is scarce. This project had
two objectives: (1) to compare spatial population structures among several closely
related species co-occurring on a common resource (cattle dung), and (2) to relate the
spatial population structures of these species to their dynamics at multiple spatial and
temporal scales.
Dung beetle movements within and between cattle pastures were studied using markrelease-recapture methods and trap-lines outside pastures. In one species, A. fossor,
migration rates were also inferred from large-scale patterns of genetic variation. The
local abundances and regional distributions of Aphodius species were estimated by a
hierarchical sampling design. Comparisons with older material then allowed me to
analyse temporal dynamics within Aphodius assemblages.
I found considerable ecological variation among Aphodius species. Interspecific differences in spatial population structures cause dissimilar spatial dynamics, as was evident
from interspecific variation in responses to contemporary landscape composition and to
habitat loss over time. During the 20th century, different dynamics among Aphodius
species have resulted in considerable changes in Finnish dung beetle assemblages, with
at least four species becoming increasingly rare, and one species expanding its
distribution. At the community level, interspecific differences in spatial population
structures make the local community composition a function of the structure of the
surrounding landscape.
Publication: No. 1222.
34
PEKKA VAKKARI
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
Monitoring population density of moths in Tvärminne
The population density of the local moth fauna has been monitored using light- and
sugar-bait-traps since 1976. The number of light traps has varied from 1 to 4; presently
2 traps are on the mainland and one in the archipelago. The bait traps (18) are operated
in 8 locations along a 6 km transect from mainland to the outer archipelago. One of the
light traps is included in the moth monitoring programme organized by the Finnish
Environment Institute and the diversity estimate of the site is quite high.
The study area has been colonized by 10–15 species during the monitoring period,
either as completely new to the area or after a long (over 10 years) absence. Among the
most remarkable records is the re-appearance of Rhyparia purpurata in 1998 and 1999,
regarded as (nearly) extinct in Finland. A few of the new species have been able to
reach significant population densities; these include Apamea scolopacina (most
abundant late-summer Apamea in some years!) and Campaea margaritata.
Melanism of moths in Southern Finland
The frequency of melanic forms in the populations of Oligia latruncula (most common
industrial melanic in Finland) has apparently started a slow decrease in the most
studied populations since 1995. The change is still very slow and far from the
spectacular case of Peppered Moth in Great Britain. Melanic forms in the local populations of the closely related Oligia strigilis are still increasing both in rural Tvärminne
and urban Helsinki area. Results from the analysis of temporal occurrence of the colour
forms support the hypothesis of selective predation as selection component in urban
areas, but time series from Tvärminne area gives variable results. It is suggested that
urban and rural melanisms in this species result from different selection pressures. The
frequency of melanic forms in 3 other species, Apatele psi, Apatele rumicis and Tethea
or, is not constant but the trend is still increasing.
Genetic structure of Oak populations in Finland
The genetic diversity and population differentiation in Pedunculate oak (Quercus
robur) populations in Finland has been studied for neutral (isozymes) and adaptive
characteristics in the field trials. The average heterozygosity for 14 isozyme loci was
estimated to be slightly lower (He=0,17) and population differentiation higher than
Central Europe (Fst=0,8). The results support the hypothesis that fragmentation affects
the genetic structure of Finnish oak populations. Characteristics of initial growth are
significantly differentiated among the studied 23 populations and the island populations
as a group are different from the mainland populations. The result may indicate the
existence of important local adaptations and has to be considered in the genetic conservation programs.
35
4. EVOLUTIONARY BIOLOGY
4.1. AQUATIC STUDIES
DIETER EBERT1, 2, CHRISTOPH HAAG1, 2, JÜRGEN W. HOTTINGER1, 2 AND V. ILMARI PAJUNEN2, 3
1
3
Zoologisches Institut, Universität Basel, Switzerland, 2Tvärminne Zoological Station and
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
The evolutionary dynamics of a Daphnia metapopulation
The rock pool inhabiting Daphnia species in the Tvärminne archipelago represent a
metapopulation with three spatial levels: the individual populations in the rock pools,
all rock pool populations on an island and the populations from all islands. We are
interested in understanding the factors, which determine the genetic population
structure on these three levels. In combination with a long-term data set on population
extinction and recolonisation (VIP) we used electrophoretic genetic markers to estimate
the number of migrants among pools and the number of founding clones for new
populations. This work revealed that most pools are colonized by single clones, an
observation consistent with the low genetic diversity within populations. Besides the
investigation on a spatial level, we are interested in the dynamics within single populations. Current projects address the role of founder effects and inbreeding and the impact
parasites have on the clonal structure of the population. We perform experiments in
natural and artificial rock pools (the latter are actually plastic pools) to elucidate which
factors determine extinction and micro-evolutionary changes in clone frequencies.
DIETER EBERT1, 2, JÜRGEN W. HOTTINGER1, 2 AND V. ILMARI PAJUNEN2, 3
1
3
Zoologisches Institut, Universität Basel, Switzerland, 2Tvärminne Zoological Station and
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
Temporal and spatial dynamics of parasites in a Daphnia metapopulation: which
factors explain parasite richness?
Several models have been suggested to explain variation in parasite richness across
host populations. Most of these models are based on epidemiological factors (population size, number of host species), biological factors (patch quality, inter-specific
competition) and spatial and temporal structure of the host metapopulation. We studied
the parasites of 137 rock pool populations of the planktonic crustacean Daphnia magna
to determine the factors which account for total parasite richness, richness of
endoparasites and epibionts and the presence/absence patterns of individual parasite
species. The rock pools of 86 of these populations have been studied since 1982 and it
is known since when these pools have been continuously inhabited by Daphnia. By far
the best predictor of total parasite richness was host population age. Sub-sampling the
data set for two functional groups of parasites (endoparasites and epibionts) and
individual parasite species revealed important details. While endoparasite richness
increased linearly with age over 16 years, epibiont richness saturated about three years
after pool colonisation, which may be explained by the higher dispersal rate of
epibionts. After correcting for the strong effect of host population age, endoparasite
richness – but not epibiont richness – correlated positively with the water volume of the
rock pool, which is an estimate for host population size. In contrast, epibiont richness –
but not endoparasite richness – correlated with water quality (conductivity). Pools with
lower water conductivity (less influenced by the brackish water of the Baltic Sea) had
more epibiont species. On a species level, it appears that inter-specific competition
among epibionts produced presence/absence patterns for certain species that are not
explained with general epidemiological and metapopulation models. The spatial
arrangement of the host populations (local pool density and number of pools per island)
36
did not influence parasite richness. In conclusion, our analysis shows that predictions
derived from general epidemiological, and temporal models (but not from spatial
models) can explain parasite richness patterns, despite apparent conflicting patterns
found for individual parasite species. Our analysis extends the scope of these models,
which have previously been mainly supported with macroparasites of vertebrates, to
microparasites in an invertebrate host.
KAI LINDSTRÖM
Department of Ecology and Systematics, Zoological Laboratory, University of Helsinki
Sexual selection, parental care and the evolution of breeding systems
This research project has two main objectives: to understand (1) the importance of
resource distribution and ecology in evolution of mating systems and (2) the evolution
of parental care and its integration within life history and sexual selection theory.
The first subunit focuses on the following more specific questions: (1) As distribution
of a resource needed for breeding changes how does this affect the distribution of
reproductive success among individuals? This is a population level approach and it
suggests that a population’s breeding system is determined by resource distribution. (2)
How does a change in resource distribution affect the costs and benefits of mate
sampling and how will this affect mate choice decisions? What traits should an
individual pay attention to in its mate choice? (3) Should parental investment depend
on resource distribution? Previous studies have suggested that breeding system evolution and parental care would be intimately connected. Parental care is a part of parental
investment and this will be one of the first studies to investigate the interaction between
resource distribution and parental investment.
The second subunit is based on the notion that males and females generally have
different means of maximizing their lifetime reproductive success. Females often invest
a lot of resource in each gamete and therefore their reproductive success is limited by
the availability of resources that can be invested into gamete production. Consequently
a female should be careful when selecting a mate in order to guarantee high survival of
her limited offspring. In species with male parental care the quality of care is a direct
benefit to the female. Therefore care quality may function as an important mate choice
criterion and thus paternal care and female mate choice may show a co-evolutionary
past. The purpose of this proposal is to construct a causal scenario for this co-evolution
both at the conceptual and empirical level. It will also investigate the heritable basis for
parental care behaviour in males and in the traits that this behaviour selects for in
females.
We use the sand goby, Pomatoschistus minutus, the common goby, P. microps, and the
short snouted pipefish, Nerophis ophidion, as model systems in studying the above
questions. Currently most work is done using laboratory experiments although some
part of the research is done in natural settings sometimes involving field experiments.
We use traditional behavioural methods as well as DNA methods to test hypotheses
generated by the above theoretical framework. Together with Dr. Marco Lugli,
University of Parma, Italy, we use underwater acoustics in order to investigating the
courtship sound of sand gobies as a potential honest signal of male quality. Preliminary
results suggest that the features of the sound produced by a male contain information
about his size and his energetic condition.
Publications: No. 1128 and
1. Lindström, K. 2000: Filial cannibalism and female mate choice strategies as resolutions to sexual conflict in fishes. – Evolution (accepted).
37
2. Lindström, K. & Lugli, M. 2000: A quantitative analysis of the courtship acoustic
behaviour and sound patterning in male sand goby, Pomatoschistus minutus. –
Environmental Biology of Fishes (accepted).
3. Lindström, K. 1998: Energetic constrains on mating performance in the sand goby. –
Behavioral Ecology 9: 297–300.
4. Lindström, K. 1998: Effects of brood care costs and benefits on filial cannibalism in
the sand goby. – Behavioral Ecology and Sociobiology 42: 101–106.
MARKKU LAHTINEN
Department of Ecology and Systematics, Division of Hydrobiology and Tvärminne Zoological
Station, University of Helsinki
Population dynamics and reproductive ecology in the sex role reversed pipefish
Nerophis ophidion
All pipefishes are sex role reversed in the sense that paternal care limits female reproductive success and females are the main competitor for mates. Of the two pipefish
species in the Baltic, the straight-nosed pipefish (Nerophis ophidion) has become by far
the more common. The reproductive biology of the species differs from most that of
other animals because the male carries the developing eggs and provides them with
nutrients and oxygen until they hatch. This increases the male parental investment to –
or over – that of the female. Females are the larger sex and only they possess sexual
ornaments. Straight-nosed pipefish are abundant around Tvärminne and they are easily
caught with a small wade net or hand trawl. All the above make it a good species for
studying parental care and sexual selection.
The work is carried out both in the field and in the laboratory. Aquaria studies focus
currently on the choice of mate(s) and whether females are capable of mating with
several males during one male pregnancy, thus affecting the operational sex ratio. The
possible conflict of interest between males and the developing young they carry is
another subject studied. Further laboratory work is done on “pregnant” males and large
females to establish the potential reproductive rates of both sexes via the amount of
eggs they carry or produce. Here digital photography is a helpful, literally lifesaving,
tool. We also observe natural mating behaviour and quantify the use of different
habitats by snorkelling and diving.
NUUTTI KANGAS AND MARKKU VIITASALO
Department of Ecology and Systematics, Division of Hydrobiology, University of Helsinki
The effect of visible predation threat on courtship of sand goby, Pomatoschistus
minutus
The idea of the study was to test the effect of predation on sexual activity of the sand
goby Pomatoschistus minutus. For testing male sexual activity, a male was let to court
a female placed in a mini aquarium inside the experimental aquarium. An aquarium
with perch, Perca fluviatilis, was placed beside the experimental aquarium to create a
visual predation threat. Male behaviour was video recorded, and swimming and
courting activity was quantified with and without the predator. In testing female sexual
activity, a female was swimming freely around a male nesting in a mini aquarium;
otherwise the experimental design was similar to the male experiments. The results
suggest that visual predation threat decreases male courtship activity and increases
female distance to male. This is consistent with the theories stating that predation risk
is a significant cost of courtship and mate choice.
38
NUUTTI KANGAS
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
Predation affects nest site colonization in the sand goby Pomatoschistus minutus
In the study area at Tvärminne suitable nest sites for sand goby Pomatoschistus
minutus are scarce. However, the factors restricting male nest building are not well
known. This study focused on the effect of predation on nest site colonization. The
predator used in the experiments was perch, Perca fluviatilis. In a field study artificial
nest sites were placed beside cages of living perch; in controls the cages were empty.
The results suggest that males are larger at safe sites than at sites close to the predator.
In a laboratory experiment, one nest site was placed beside a perch aquarium without a
shelter and one nest site behind an opaque shelter further away from the perch. Most of
the males built nests at sheltered sites suggesting that males do avoid risks in nest
building. In conclusion, predation may affect nest site colonization, and competition for
safe nest sites in natural conditions may determine the local distribution of breeding
males.
ULRIKA CANDOLIN
Section of Ecology, Department of Biology, University of Turku
Honesty of sexual signalling in the threespine stickleback
According to the theory of sexual selection, secondary sexual characters are ultimately
restricted from further elaboration by opposing natural selection. In this study I
determined different environmental factors and intrinsic properties of the male that
restrict red nuptial coloration and courtship behaviour in threespine stickleback males,
Gasterosteus aculeatus. I especially went into the importance of predation risk as a
constraining factor and show how several other factors in turn modify the effect of
predators on signalling.
For females to benefit from mate choice based on the elaboration of sexual signals, the
signals should honestly reflect the quality of a male. An intriguing possibility is that the
honesty of signals is ensured by the cost of signalling. I therefore investigated different
mechanisms that could maintain reliable signalling, i.e. signals as indicators of
predation susceptibility, condition-dependent signalling, signals as badges of status,
and multiple signalling. My results point to the importance of the presence of predators
and male–male competition in ensuring reliable signalling. The effect of predators on
signalling is not uniform among males, but depends on the male’s ability to escape
predators and his success in the competition for favourable times and places for
reproduction. A social control of deception increases in turn the honesty of the signals
in relation to male dominance. A confounding factor was residual reproductive value.
Males increased their signalling effort when conditions deteriorated and future
reproductive opportunities decreased. However, it is possible that natural selection
could decrease the frequency of cheaters and maintain reliable signalling on average.
Publications: Nos. 1175, 1191, 1192, 1207 and 1214.
39
4.2. TERRESTRIAL STUDIES
LISELOTTE SUNDSTRÖM, MINTTUMAARIA HANNONEN, PAUL STEVENS, HEIKKI HELANTERÄ AND
KALEVI TRONTTI
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
The evolution of colony characteristics in social insects
The evolution of insect sociality is one of the key research areas in behavioural ecology, population genetics and evolutionary biology. To date, a large body of theoretical
work has focussed on processes causing variation in the kin structure of insect colonies
and the evolutionary consequences of such variability. This work centers on Hamilton's
rule and the principle of inclusive fitness, which provides a basis for understanding the
evolution of sociality, as well as a framework for predicting the evolution of colony
characteristics in social insects. Recent theory predicts different optimal strategies by
colonies with different genetic make-ups. A detailed knowledge of colony kin structure
requires powerful genetic methods, which now are available through refined DNAtechniques.
The scientific interest of studying social conflicts in ants, bees and wasps goes much
beyond these social insect groups themselves. Knowing the relatedness between
interacting parties, means that the power of natural selection can be quantified. General
questions that our group studies are: (1) The extent to which precise behavioural
adaptations are possible for individuals maximising their reproductive success, and
which proximate factors may constrain optimal solutions. (2) How productivity aspects
of unrestricted cooperation are traded off against selfish reproductive interests. (3)
What is the significance of information processing for ergonomic efficiency and social
cohesion on the one hand, and for the resolution of reproductive conflicts on the other?
Our aim is to address both aspects of cooperation and conflicts in colony life and
thereby to reach a deeper understanding of the evolutionary forces that shape functional
aspects and the nature and resolution of conflicts within insect societies. To accomplish
this we use ecological and genetic approaches to analyse the causes and consequences
of between-colony variation in within-colony genetic heterogeneity.
Publications:
1. Sundström, L., Chapuisat, M. & Keller, L. 1996: Conditional manipulation of sex
ratios by ant workers: A test of kin selection theory. – Science 274: 993–995
2. Chapuisat, M., Sundström, L. & Keller, L. 1997: The economics of fratricide in ants.
– Proc. R. Soc. Lond. B. 264: 1255–1260
3. Sundström, L. & Ratnieks, F. L. W. 1998: Sex ratio conflicts, mating frequency and
queen fitness in Formica ants. – Behavioral Ecology 9(2): 116–122.
4. Boomsma, J. J. & Sundström, L. 1998: Paternity patterns in Formica ants. – Behav.
Ecol. Sociobiol. 42: 85–92
5. Walin, L., Sundström, L., Seppä, P. & Rosengren, R. 1998: Worker reproduction in
ants – a genetic analysis. – Heredity 81: 604–612.
40
LISELOTTE SUNDSTRÖM
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
Social life in ants – the battle between mothers, fathers and daughters
In social insects two research traditions prevail: on the one hand colonies comprise a
cooperative unit in which all individuals act for the common good, on the other hand
colony members are not genetically identical and can be expected to act purely in their
own interest. The latter view is derived from inclusive fitness theory, which predicts
that sociality and a reduced personal reproduction can be in the best interest of some
individuals. In giving up their personal reproduction, however, such individuals will be
expected to act so as to maximise their inclusive fitness. When analysing predictions
emanating from inclusive fitness theory relatedness between the interacting individuals
plays a key role, since relatedness directly translates into genes that are transferred to
the next generation.
Social Hymenoptera pose a special case here, since their sex determination system
causes females to be more closely related to sisters than to brothers, or even to their
own offspring. This is defined as the relatedness asymmetry. A mother, by contrast, is
equally related to both sons and daughters. These asymmetries in genetic relationships
among colony members cause a number of primary (e.g. over sex allocation and worker
reproduction), and secondary conflicts (e.g. between queens and males). Complexity is
added by the occurrence of multiple queening and multiple mating by queens.
The results strongly suggest that workers control the allocation of resources into males
and females, and that the conflict is actual. Experiments have shown that workers
selectively remove male eggs in colonies headed by single-mated queens, but refrain
from doing so if the mother queen is multiple mated. The project continues with
analyses of the effects of multiple queens and multiple nest sites per colony.
Life history strategies in ants
An inclusive fitness approach allows the quantification of natural selection because the
parameter r (relatedness) can be estimated using genetic markers. Hence the momentary reproductive success of a queen can be estimated from the sex ratio of her brood
corrected by her relatedness to it, whereas her life time reproductive success can be
estimated by tracking the origin of queens in newly founded colonies based on the
same genetic markers. Such information can be combined with long-term data on
colony productivity to assess reproductive success over time.
The observed sex ratio is most likely the result of several interacting factors, inclusive
fitness arguments being one. In addition to colony kin structure two mutually nonexclusive resource-based hypotheses have been presented to explain colony-level sex
allocation patterns. First, resource availability may directly affect colony sex ratios
such that a larger fraction of the diploid brood is channelled into reproductive females
under high resource levels, whereas diploid brood instead is channelled into new
workers if resources are low. Second, differential dispersal of the sexes may result in
different degrees of local mate competition or local resource competition. The relative
importance of genetic versus environmental factors can be separated by experimental
manipulation of resource levels to assess whether colonies respond by redistributing the
available resources between the different types of brood (males, females).
The study species are Formica truncorum and F. exsecta, both of which occur
commonly on archipelago islands around the Zoological station. The project started in
1992 and still continues. All colonies of the above two species are censused each year
for sex allocation ratios, colony size and productivity.
41
LISELOTTE SUNDSTRÖM1 AND KOOS BOOMSMA2
1
Division of Population Biology, Department of Ecology and Systematics, University of Helsinki,
2
Department of Population Ecology, Zoological Institute, University of Copenhagen, Denmark
Facultative sex ratio biasing and male-female conflicts in ants
Empirical studies have shown that workers in several species of ants are able to
manipulate sex allocation ratios in their favour. In particular, workers in single queen
colonies were shown to alter colony sex ratios in accordance with queen mating
frequency, such that colonies headed by single-mated queens specialize in female
production and those headed by multiple-mated queens specialize in male production.
These findings have resulted in further theoretical developments concerning the opposing interests of colony queens and their male mates. As a result of the haplodiploid sex
determining system males never father sons, hence a male that ends up co-siring a
colony faces zero fitness, if, as predicted by theory, the workers rear an all-male sexual
brood. Males may, however, have evolved various mechanisms to mitigate such worker
manipulation, such that also colonies with multiple-mated queens produce at least some
females. One way to accomplish this is by sperm clumping, where sperm from each of
two fathers is used in alternating bouts through time. Another way is by male continence where a second male transfers a small amount of sperm. In both cases a high
enough relatedness asymmetry may ensue to cause the production of female-only
brood, in accordance with male preferences. In this study we analyse the year-to-year
variance in paternity shares and sex allocation in Formica truncorum, an ant with longlived perennial colonies. Furthermore we analyse the effect of mating order on the
proportion of offspring fathered, to evaluate the male continence hypothesis.
MINTTUMAARIA HANNONEN, LISELOTTE SUNDSTRÖM AND KALEVI TRONTTI
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
Queen number and mating patterns in the ant Formica fusca
Ant societies vary greatly in their colony kin structure both within and between species.
Such variation arises because colonies on the one hand have different numbers of
mothers and fathers and on the other hand relatedness varies among reproductives.
Variation in kin structure often affects the genetic population structure.
Here we study the effective queen number, queen mating frequency and genetic population structure of the ant Formica fusca. We have been studying a population of this
species since the year 1997. The species has previously been considered only weakly
polygynous1,2. In our study population, however, queen number varies between one and
more than twenty.
Queens and workers were highly related and there was a positive inbreeding value
within workers, which might suggest the occurrence of two subspecies in the study
population. However, the non-significant inbreeding value in queens excludes this
possibility. Queens were related to their male mates, which is expected given the
observed inbreeding among workers and suggests that male dispersal is limited. Also
the males fathering the same colony were related.
In future studies we will expand this data set to encompass also populations from
Tvärminne archipelago and Inkoo archipelago to see whether there are differences
between populations in the aspects mentioned above.
Publications: 1188 and
1. Rosengren, R., Sundström, L. & Fortelius, W. 1993: Monogyny and polygyny in
Formica ants: the result of alternative dispersal strategies. – In: Keller, L. (ed.),
Queen number and sociality in insects. Oxford University Press. pp. 308–333.
42
MINTTUMAARIA HANNONEN AND LISELOTTE SUNDSTRÖM
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
Reproductive competition among multiple queens in the ant Formica fusca
Ant colonies in many species contain multiple queens. When several queens share the
resources of one colony they usually experience a reduction in their personal reproduction. Reproduction among queens may be unequal and there may also exist dominance
hierarchies among them. Reproductive skew describes the distribution of direct
reproduction among cobreeding individuals. Recent models of reproductive skew
predict how reproduction should be shared among cobreeding individuals. According
to the models the relatedness of the cobreeding individuals should correlate with the
reproductive skew among cobreeders.
We tested this prediction by observing the sharing of reproduction among Formica
fusca queens reared in laboratory nests. Queens and offspring were genotyped using
allozyme and DNA microsatellite markers. The number of offspring produced by each
queen was assessed and queen-queen relatedness was estimated. Queens within the
nests were highly related and reproduction was skewed. The degree of skew correlated
negatively with the relatedness between nestmate queens. Queen size had no effect on
the dominance over reproduction. In future we will concentrate on proximate reasons
of skewed reproduction, which will include studies of queen behaviour and queens’
chemical profiles.
HEIKKI HELANTERÄ AND LISELOTTE SUNDSTRÖM
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
Worker reproduction in the ant Formica fusca
In social insect colonies potential conflicts between queen and workers arise over sex
allocation and male production. We studied different aspects of the conflict over male
production in Formica fusca both by direct observations and experimental manipulations of social conditions. Workers of this species readily lay male eggs but in queen
right laboratory colonies only worker offspring are reared. Worker reproduction is
expected in our study population based on relatedness arguments. In this study we
addressed three main questions. First, we tested the effect of social conditions on the
production of new workers vs. sexuals. We did this both by limiting the queens’ mobility within the nests and by removing queens after eggs had been laid. Both treatments
increased the probability of sexual offspring being reared in the nest. Second, to find
out whether an actual conflict over male production exists we screened eggs from
queen right colonies using DNA microsatellites to assess the origin of male eggs. The
amount of worker laid eggs found was very low. Third, we created a conflict in the nest
by transferring reciprocally eggs from queenless colonies to queen right colonies both
originating from the same field colony. We also manipulated queen access to brood to
tell apart worker policing from queen policing. Some transferred eggs were reared into
sexuals in queen right colonies which suggests incomplete policing. The overall results
suggest the presence of actual conflict over male production and a strong queen effect
in its outcome.
KALEVI TRONTTI AND LISELOTTE SUNDSTRÖM
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
Worker control over colony reproduction in the ant, Formica fusca
Fitness of the worker caste in social insects depends not only on the number of sexuals
produced but also on the sex ratio. Due to the haplodiploid sex determination workers
43
should, to maximise their fitness, generally prefer to produce female biased sex ratios
as they share more genes with females than with males. By contrast, the queens prefer
an even investment in males and females. Hence a conflict arises between workers and
queens over what sex ratio to produce. Similarly, a conflict may occur over male production, because workers of many ant species are able to lay unfertilised eggs that develop into males. The strength of these conflicts depend on the exact relatedness patterns. In general, the more individuals in a colony are related, the stronger the conflict.
Our species of interest, Formica fusca, has mainly single-queen colonies. However
queens differ in mating frequency which causes a differences in colony-level relatedness. Additionally, workers are able to lay viable haploid eggs. In this study we
investigate whether these predicted conflicts are realised in colonies of this species, i.e.
do workers bias the sex ratio produced by queen and/or do they use their ability to lay
eggs. Thus, the ultimate question in this study is: which party wins? The work is
carried out by inspecting egg and pupal brood collected from natural colonies on two
islands of Tvärminne archipelago. Sex ratio changes between these developmental
phases can be interpreted as worker control. We also determine the amount of worker
produced males. The identification of the origin of male offspring and the sex of early
brood is carried out using microsatellite markers.
VIENNA SETÄLÄ AND LISELOTTE SUNDSTRÖM
Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
Dispersal patterns and mating system in the ant Lasius flavus
The aim of this work is to address both aspects of cooperation and conflicts in eusocial
insects, and to understand the evolutionary forces that shape the functional strategies of
ant colonies. We use ecological and genetic approaches to (1) analyse dispersal patterns
and mating system, (2) study the effect of genetic diversity on fitness during colony
founding at both the individual and the colony level, by making experimental manipulations, and (3) find out how intra colony conflicts over reproduction are resolved.
Knowing of the relatedness between the parties in the system studied, allows quantification of the magnitude of natural selection and to analyse and predict the functional
patterns of complex systems. The results thus may have wider implications than only
describing a social system like an ant colony. The work also gives valuable information
of basic biology of the species studied and the selection pressures its populations are
faced. These data can be used to identify at an early stage species which may become
threatened, for example, because of habitat fragmentation.
WOJCIECH CZECHOWSKI
Museum and Institute of Zoology, Polish Academy of Sciences
Settlement of wood ants on rocky islands after artificial colonization (in collaboration with K. Vepsäläinen)
In 1987, nine colonies of wood ants (Formica polyctena, F. aquilonia, F. lugubris, F.
truncorum, F. exsecta), and in 1995, two other ones were artificially established on
small rocky islands in the Tvärminne archipelago, which originally lacked them. Five
colonies of the first group and one of the second group were extant in 1999. This, and
observations on mated queens on remote islands suggests that the immigrant queens,
though successful in their dispersal, are not able to establish new colonies. As it is
suggested, the main obstacle to colonization of islands by territorial wood ants may be
the local scarcity of temporal host species (i.e. Serviformica ants) used by wood ant
queens for founding their new colonies or (and) the predation from some other resident
ants.
44
Even on a very small island, habitat may be suitable enough for wood ants: the experimental F. aquilonia colony on Kvarnskarsgrunden has developed successfully, thriving
now on almost bare rock, and supplied mainly by food from aphids in a solitary pine
and insects (mainly chironomids) drifting to the island. What is puzzling, this colony
uses only a small part of the accessible area and its territory is much smaller than
territories of colonies of similar size that live in normal habitats. Maybe, it is because
of the lack of competition from other territorial ants. To solve this question, the second
conspecific colony were established on the same island in 1999. At the same time, the
relations between artificially introduced ants and resident ones are observed.
Publications: No. 1219 and
1. Czechowski W. & Vepsäläinen K: Existence of wood ant colonies (Hymenoptera:
Formicidae) under extremely difficult habitat conditions – a manipulation
experiment. – In prep.
Socially parasitic interspecific relations in ants: relations between Formica
sanguinea and Formica cinerea (Formicidae)
Formica sanguinea, a facultatively dulotic ant, uses a very specific way to obtain
slaves from colonies of F. cinerea (the subgenus Serviformica). The enslavement
follows periodic invasions and temporary occupation of nests of the slave species by
the slave-maker. During the occupation of their nest, some adult F. cinerea workers
join the occupant colony. The studies, started earlier in Poland, have been carried out in
Tvärminne in the years 1996–1999.
Publications:
1. Czechowski, W. & Rotkiewicz, W.: Relations between Formica sanguinea Latr. and
Formica cinerea cinerea Mayr (Hymenoptera, Formicidae) – an unusual form of
dulosis. – Ann. Zool. (in press).
Colonies of hybrids and mixed colonies: interspecific nest takeover in wood ants
Synthetic work consisted of two parts: Part I concerns relations within the Formica
rufa group, Part II describes relations between wood ants and dulotic ants Formica
sanguinea. The studies were carried out from 1985 to 1996 in Poland and in Tvärminne
archipelago. They consisted in long-term observations of natural colonies and in field
and laboratory experiments. In Part I the occurrence of wood ants in the Gorce Mts (S
Poland) is presented and evidence of the difference between the local populations of F.
polyctena and F. rufa is provided. Biometrical analyses indicate that these forms are
also morphologically different. Moreover, proof has been found for the existence of
hybrids F. rufa x F. polyctena consisted of three phenotypes of workers (rufa-like,
intermediate, polyctena-like). Some cases are also described of spontaneous changes in
the specificity of colonies which follow adoption of specifically alien queens by
orphaned workers. Thus it has been proved that temporarily mixed colonies of wood
ants do exist. The results are presented against the background of taxonomic problems
posed by these ants. Part II presents functioning of F. sanguinea colonies with wood
ants as their (atypical) slaves and discusses mechanisms of slave emancipation and of
nest takeover by the slave species. The latter are: (1) extermination of F. sanguinea
brood which, being younger than pupae of the atypical slave species, are selectively
devoured in a mixed colony facing starvation; (2) recruitment of conspecific queens by
atypical slaves during temporary splits of a mixed colony; (3) temporary bispecific
oligogyny of the society; (4) elimination of the legitimate queen as a result of
antagonism between queens encountering one another. The final section includes a
survey of the ways wood ant queens may achieve reproductive success.
Publication: No. 1132.
45
SARI HAIKOLA1, 2 AND ILKKA HANSKI2
1
Tvärminne Zoological Station and 2Department of Ecology and Systematics, Division of Population Biology, University of Helsinki
Inbreeding depression in the butterfly Melitaea cinxia
Harmful effects of small population size and inbreeding have been documented in
many animal species. On the grounds of numerous studies it can be concluded that
inbreeding lowers general viability of an individual. The magnitude of inbreeding
depression can be great in some species, and its consequences in natural populations
may have been generally underestimated. Our problem is the difficulty of measuring
inbreeding depression in all possible life stages. It has been claimed that inbreeding
depression should be low in species that have experienced inbreeding in the past.
Nonetheless, there is also evidence suggesting that even highly inbred populations can
suffer from inbreeding depression of high magnitude. The aim of our study is to
quantify possible inbreeding depression in the butterfly Melitaea cinxia and to clarify
the possible relationship between the magnitude of inbreeding depression and population`s past inbreeding history. Presently our rearings include 40 larval families, which
are the result of sibmatings or interpopulation crosses in previous generation. The
results so far indicate a significant reduction in fitness due to inbreeding, the effect
being more severe within continuous than naturally fragmented populations. These
results are important against the background of continuing destruction of natural habitats by human activities. This project is a part of an extensive research program on the
metapopulation dynamics of Melitaea cinxia, directed by professor Ilkka Hanski, and it
has been conducted at Tvärminne Zoological Station since 1996. During these years the
laboratory conditions and the rearing routines have been developed to an appropriate
level to facilitate our experimental research.
MARKUS ÖST AND MIKAEL KILPI
Department of Ecology and Systematics, Zoological Laboratory, University of Helsinki
Eider females and broods from neighbouring colonies use segregated local feeding
areas
We studied the post-nesting site use of Eider Somateria mollissima females in the
northern Baltic in 1997-98. We compared the dispersal pattern of lone tenders, multifemale tenders and females without young. We also examined if females from the same
colony used the same sites and if the sites of birds from neighbouring colonies were
segregated. Primary movements were similar in length irrespective of female breeding
status or colony, whereas lone tenders tended to undertake shorter secondary
movements than females without young. The home range of females was similar
irrespective of breeding status or time of the breeding season, but it was significantly
smaller in the outer study area than in the innermost Eider colony. Blue mussels are
more abundant in the outer area, so food resources may influence home range size.
Home range size correlated positively with the number of ducklings in broods,
indicating that large broods need more food and a larger feeding area. Females from the
same colony were aggregated to the same sites close (<1 km) to their nesting island. A
long-distance nest exodus after hatch was absent, an obligatory feature of many Eider
populations elsewhere. The sites of neighbouring colonies were spatially separated.
This may be due to females moving to the nearest available feeding site, or mutual
avoidance or aggression between females from different colonies. Solitary females
were present at the colony throughout the breeding season. These females could be
prospecting for safe nest sites, outweighing the need to move to better feeding grounds.
Our results indicate that familiarity with post-nesting feeding sites may be
advantageous during brood-rearing. Multi-female tenders may originate from the same
46
island, opening up the possibility that kin selection or reciprocity might affect posthatch brood amalgamation behaviour.
MARKUS ÖST
Department of Ecology and Systematics, Zoological Laboratory, University of Helsinki
Within-season and between-year variation in the structure of Common Eider
broods
I studied within-season and between-year variation in Common Eider (Somateria
mollissima) brood structure, by censusing broods in the northern Baltic in 1995-98. I
also examined within-season patterns of female aggressiveness, and explored whether
between-year patterns could be related to female body condition at hatching. Multifemale tending was initially the dominant brood rearing strategy. Moreover, 25–38 %
of the lone-tended broods had more than six ducklings, indicating that they may
contain adopted young. The number of ducklings per female increased with brood size,
exposing some newly hatched ducklings to chilling due to unfavourably high ratios of
ducklings to brooding females. Lone tenders became proportionally more common, the
proportion of two-female tended broods was stable, and the proportion of broods with
more than two females rapidly decreased during the season. Female aggression
decreased in frequency over time, so the decline of broods with more than two females
may relate to female aggressiveness. Family units began to break up when ducklings
were 7 weeks old. Multi-female broods were initially more common in years when
females were in good condition at hatching and less common in years when females
were in poor condition. However, multi-female broods decreased in frequency over
time in all years except the poorest year; multi-female tending strategy was most
common in poor years and least common in good years. These between-year patterns
may result from differences in body condition between lone tenders and multi-female
tenders, indicating that female body condition may affect brood-caring decisions.
MARKUS ÖST1 AND MARTTI HARIO2
1
Department of Ecology and Systematics, University of Helsinki, 2Finnish Game and Fisheries
Research Institute, Söderskär Game Research Station
The effect of local food resources on feeding and breeding performance of a
migrant capital breeder, the Eider Somateria mollissima
We studied pre-laying foraging behaviour and breeding performance of Eiders nesting
at two different localities in the Gulf of Finland in 1996–98. The Eider population has
declined significantly at the eastern site (Söderskär), while the population at the
western site (Tvärminne) has been fairly stable. The availability of food, measured as
the density and biomass of blue mussels, differed significantly between these localities.
The length of foraging cycles and the time devoted to active feeding were considerably
greater among females at Söderskär with less available food. However, clutch size and
female body weight at incubation onset were similar in both areas. Pre-laying foraging
behaviour was similar among years at Söderskär, despite annual differences in clutch
size and body weight at incubation onset. In addition, annual differences in clutch size
and weights at incubation onset showed slight parallelism between localities. These
results suggest that food at the breeding grounds is mainly for maintenance, and that
reserves acquired prior to arrival regulate the breeding performance of this migrant
capital breeder. Local food conditions had little impact on clutch size variation of
breeding Eiders, but at Söderskär the production of fledglings has been seriously
depressed. Therefore, if the decline in blue mussel populations in the Gulf of Finland
contributes to the population decrease of Eiders, it probably acts via juvenile survival
rather than via clutch size.
47
5. ECOPHYSIOLOGY AND ECOTOXICOLOGY
LIISA VAINIO1, MAGNUS LINDSTRÖM2 AND EILA LAHDES3
1
Laboratory of Animal Physiology, Department of Biology, University of Turku, 2Tvärminne
Zoological Station, 3Finnish Institute of Marine Research
Behavioural thermoregulation by the cold-adapted amphipod Monoporeia affinis
Freely moving poikilotherms can respond to changes in the environment by moving
towards the preferred temperature. This phenomenon is called behavioural thermoregulation. The amphipod Monoporeia affinis from moderate depths at which temperature changes normally occur is known to migrate in the direction of higher temperature
in temperature gradients974, 982. Our hypothesis is that animals living in constantly cold
conditions would lack preference for higher temperatures. M. affinis from deep,
permanently cold, water (2–3 °C) are tested in a toroidal arena in which steep temperature gradients from 2–20 °C can be created. The experiments last 5 hours. Our preliminary results show that the animals quickly settle down in the sand at the warm end of
the arena although introduced at the cold end. The preferred temperatures seem to be
around 16–17 °C (max temp. 18.5 °C). Next step includes combinations of temperature
gradients and water oxygen level. The project continues as a collaboration between the
three institutes.
Publication:
1. Kivivuori, L.A., Lindström, M. & Lahdes, E.O. 1999: Behavioural thermoregulation
and swimming activity of the cold-adapted amphipod Monoporeia affinis. – XXth
ESCPB Conference; Molecular, physiological and behavioural adaptations to
environmental factors. Aarhus, Denmark, 27th–30th June 1999. Abstract.
ALBERTO UGOLINI1, MAGNUS LINDSTRÖM2, BRUNO TIRIBILLI3 AND CARLO CASTELLINI3
1
3
Department of Animal Biology, University of Firenze, Italy, 2Tvärminne Zoological Station and
Instituto Nazionale di Ottica, Firenze, Italy
Findings on the vision of the sandhopper (Talitrus saltator: Amphipoda:
Crustacea); evidence for UV vision
The semi-terrestrial amphipod Talitrus saltator lives along the strand line of sandy
beaches. They have a highly accurate circadian pattern of emergence and re-burrowing,
which continues also in constant conditions. Their orientation towards the shoreline
and back has been shown to depend on celestial clues. Their endogenous biological
clock is adjusted to the daily light cycle and the local directions. If transferred to a
shore going in another direction they are not able to orient themselves properly. T.
saltator can use the sun as a celestial clue only at wavelengths <450 nm when tested
with filters above the experimental enclosure. At wavelengths longer than 500 nm the
sight of the sun and the sky only induced phototactic behaviour. It has been shown that
T. saltator perceives at least one orienting factor in deep blue, and this factor might be
polarisation1119. Recording the electroretinogram from darkadapted animals we found a
broad spectral sensitivity curve with high sensitivity in the blue part of the spectrum.
By selective adaptation we separated two pigments or pigment mixtures, with maxima
at about 435 and 500–567 nm, respectively. There are indications of a UV-sensitive
pigment which is bleached faster than the other two pigments, maybe because of lack
of wavelengths needed for light-induced re-isomerisation1042 in the laboratory. This
problem will be scrutinized next. The investigation continues as a collaboration project
between the three institutes.
48
Publications: Nos. 1042, 1119 and
1. Ugolini, A., Meucci, L., Tiribilli, B. & Lindström, M. 1999: Celestial orientation and
spectral filtering in Talitrus saltator and Tylos europaeus (Crustacea, Peracarida). –
CNR-ICB, Oristano 1999: Vision, behaviour and the marine environment.
ALEXANDER DONTSOV1, IRINA FEDOROVICH1, MAGNUS LINDSTRÖM2, MICHAIL OSTROVSKY1
1
Institute of Biochemical Physics of the Russian Academy of Sciences, Moscow, Russia, ²Tvärminne
Zoological Station
Comparison of the antioxidant properties of eye tissues from two populations of
Mysis relicta living in different light environments
The opossum shrimp Mysis relicta sp. I (Crustacea, Mysidacea) from Lake Pääjärvi
differs markedly in tolerance to light induced damage878 from the population living in
the Pojo Bay. The eyes of the two populations contain different amounts of ommochrome screening pigment in their eyes1211. The antioxidative status of the eyes of the
two groups were compared using eye homogenates. We compared the potential ability
to accumulate the products of oxidation in the eye’s tissues by examining the Fe2+induced lipid-hydroperoxide accumulation. This was estimated in presence of glutathione peroxidase spectrophotometrically as an absorption decrease at 340 nm. The
lake population was more sensitive to oxidation: the rate of accumulation was almost
twice as high as in the eyes of the sea population. These data are in good agreement
with our previous results1211. The activity of the antioxidant enzymes – superoxide
dismutase and glutathione peroxidase – was measured in the water soluble fraction of
eye tissue homogenates. For the lake mysids the activity of superoxide dismutase was
17.0 ± 0.8 and for the sea mysids 12.6 ± 0.9 units/mg protein. The activity of glutathione peroxidase was 3.2 ± 0.4 and 4.6 ± 0.3 nmoles/min mg protein respectively. The
enzyme activities were thus practically equal in both populations. We propose that the
difference in sensitivity to oxidation is determined by some other antioxidant system,
probably ommochromes. The investigation continues as a collaboration between the
Russian and Finnish Academies of Science.
Publication: No. 1211.
VESA SIPIÄ AND HARRI KANKAANPÄÄ
Finnish Institute of Marine Research
The transfer of cyanobacterial hepatotoxins into mussel tissues − a pilot study
The transfer of cyanobacterial hepatotoxins (nodularin or microcystins) into blue
mussels Mytilus edulis was studied near the Tvärminne Zoological Station, western
Gulf of Finland. Nodularin (NODLN) is produced by a cyanobacterium Nodularia
spumigena. Microcystin (MC) producers can be found e.g. in the genera Anabaena,
Microcystis and Oscillatoria. About 2000 blue mussels, collected from Storgadden,
were acclimated for two weeks in seawater pools, during which they also attached
themselves on the sediment plates provided in the pools. After two weeks the plates
with attached mussels were transferred into two steel cages (1.5 sq.m, 1000 specimens/cage) and incubated in the sea (Sundholm Sound) at the depths of 3 meters.
Every 3–4 weeks ca. 200 specimens were sampled from each depth by diving. The
pooled samples were then homogenised, freeze-dried and stored at –25 °C for the toxin
analysis. Plankton samples were also taken from the surface layer (0–3 m) during the
mussel samplings. Unfortunately, the semi quantitative plankton analysis showed only
very low concentrations of Nodularia in the study area which may have severely
hampered our experiment. Instead, plankton samples contained higher amounts of
Anabaena, Aphanizomenon and Oscillatoriales. The analysis of NODLN using ELISA
49
(Enzyme–Linked Immunosorbent Assay) showed that the soft tissues of mussels
contained cyanobacterial hepatotoxins (NODLN or MC) at least several hundred
nanograms. The experiment will be repeated during the summer 2000 using both
littoral and pelagial sea areas for incubation.
JORMA KOHO
Tvärminne Zoological Station
Mechanism of fluctuations in year class size of fish larvae – an individual size
based approach for coregonids
Large variation in year class strength has been well documented for many marine and
freshwater fish species. It is generally assumed that the variability in the recruitment of
fish initially originates in the early life history via variability in mortality of eggs and
larvae, but in spite of a lot of research, no general explanation exists as to their causes.
In this contribution, the development of vendace (Coregonus albula) and whitefish (C.
lavaretus) year classes from egg to larvae stages was investigated in field conditions
and in the laboratory as well as by using computerized simulation modelling.
Coregonid spawners were caught with gill nets at the end of October or during
November at their spawning grounds in different parts of Lake Saimaa and north of
Hanko peninsula in the Baltic Sea, in 1985−1999. Ripe fish were stripped and fertilized. Water-hardened eggs were then transferred to egg incubators in the laboratory at
the University of Joensuu and Tvärminne Zoological Station. Eggs were subsequently
divided into the specific test groups. The effects of water temperature and oxygen
concentration on the development of year-classes were studied both in laboratory and
in field conditions. Instantaneous dry mass and composition (elements H, C, N) of eggs
and embryos were determined at different phases of the egg development. Egg
metabolism was measured as the heat dissipation and was also estimated from the dry
mass loss of eggs and hatched embryos at different ages. The effects of zooplankton
density and water temperature on larval growth, survival, food selection and swimming
activity were studied in the laboratory. The influence of type of prey and temperature
on the gastric evacuation rate of larvae was also examined.
Computer simulations were applied to reveal the interactions between larval survival
and dry mass of eggs, water temperature, and predation pressure. These studies showed
that (1) the metabolic rate of eggs depends on the egg size, (2) the duration of the
incubation period reflects the size of embryos, (3) survival of larvae depends on the
water temperature and predation pressure. It was shown that decrease in incubation
temperature as well as increase in water temperature after hatching both beneficially
increase the survival of larvae if feeding is not the limiting factor. Long incubation
period maximizes the hatching size of larvae, while the high growth temperature after
hatching maximizes the growth rate of larvae. The variability in the duration of larval
phase reflects the size dependent mortality (predation) of larvae. This variability
generates the variation in year-class strength of fish.
MIKAELA GRANQVIST1 AND EVA SANDBERG-KILPI2
1
Åbo Akademi University, 2Tvärminne Zoological Station
Tolerance of the eelpout, Zoarces viviparus (L.), to oxygen deficiency and its
predation efficiency under short-term hypoxia
Oxygen deficiency, as a consequence of eutrophication, occurs today in many coastal
as well as deeper areas. Important biotic interactions in the benthic community, such as
predator−prey relationships, may be affected due to species-specific tolerances to
oxygen deficiency.
50
Experiments in aquaria were conducted to study the tolerance (LT50-value) of the
eelpout, Zoarces viviparus, to oxygen deficiency induced by (1) N2-bubbling and (2)
under macroalgal mats. In the case of N2-bubbling, 50 % of the eelpouts survived over
2 h in 2.1–4.4 % O2 saturation, 23 h in 10 % O2 saturation and at least 7 days in 40 %
and 20 % O2 saturation. Under the algal mats the oxygen level decreased rapidly (from
>95 % O2 to 4.6 % O2 in 23 h) and the LT50-value of the eelpout was 24 h.
The predation efficiency of the eelpout was studied using the Baltic clam, Macoma
balthica, and amphipods (Gammarus spp.) as prey. Experiments were conducted at 100
%, 40 % and 20 % O2 saturation for 48 h. M. balthica was not consumed during the
experiments. The predation efficiency on Gammarus spp. was highest (90 % of the
prey consumed) in normoxia, but no significant difference in the consumption of
Gammarus spp. was found between different O2 saturation.
This study shows that the eelpout has a relatively high tolerance to short-term severe
hypoxia and long-term moderate hypoxia and that its predation efficiency does not
significantly decrease under short-term hypoxia.
HEINZ-RUDOLF VOIGT
Department of Limnology and Environmental Protection, University of Helsinki
Concentrations of heavy metals and health condition of selected species of coastal
fish around the Baltic Sea
The above title covers several projects being done in cooperation with both domestic
and foreign colleagues. The main fish species studied are smelt (Osmerus eperlanus),
herring (Clupea harengus membras), sprat (Sprattus sprattus balticus), eelpout
(Zoarces viviparus), flounder (Platichthys flesus), turbot (Psetta maxima), fourhorn
sculpin (Myoxocephalus quadricornis) and bullrout (M. scorpius). Other species of
interest are pike (Esox lucius), perch (Perca fluviatilis), ruffe (Gymnocephalus
cernuum), and three-spined stickleback (Gasterosteus aculeatus). The metals analysed
are mercury (Hg), iron (Fe), manganese (Mn), zink (Zn), copper (Cu), cadmium (Cd),
lead (Pb) and nickel (Ni). The Finnish study area includes the waters off Tvärminne
and some locations in the Archipelago Sea, SW Finland, and around the Åland Islands.
In Estonia sampling takes place both on the northern and western coasts and in Latvia
in the Gulf of Riga. In Germany sampling takes place on the waters off and in the Firth
of Kiel.
The projects include e.g.:
1. Concentrations of heavy metals and health condition of two partly food-competing
pelagic species, smelt and herring, from Finnish and Estonian coastal waters,
2. Concentrations of heavy metals in two foodcompeting sculpins; fourhorn sculpin and
bullrot from Finnish and Estonian coastal waters.
3. Concentrations of heavy metals and health condition of flounders and turbots from
coastal waters of SW Finland and the Firth of Kiel, N Germany,
4. Concentrations of heavy metals and growth of eelpouts from Finnish and Latvian
coastal waters,
5. Concentrations of mercury in perch from the Tvärminne archipelago.
So far we have found that concentrations of mercury are higher in inshore coastal
species than in the more open-sea species, in predatory species than in the nonpredatory species and they also increase by the age of the fish. The mean concentrations of mercury are higher in flounders from Tvärminne than in flounders from the
Kiel area. A positive correlation exists between mercury concentrations and liver
lesions in Finnish flounders. Manganese concentrations are higher in smelt than in the
51
two clupeids, sprat and herring. Concentrations of cadmium are high in herring from
Estonia, in flounder from SW Finland and Åland and in eelpout from SW Finland.
Nickel concentrations are higher in fish from SW Finland and Kiel than in fish from the
other sampling stations.
Publication:
1. Voigt, H.-R.: Concentration of heavy metals in fish from coastal waters around the
Baltic Sea. – ICES Journal of Marine Science 57 (in print).
2. Voigt, H.-R.: Heavy metals and organochlorine levels in coastal fish from the Väike
Väin Strait. – Estonian Academy of Science 49 (4) (in print).
6. MISCELLANEOUS
GUY HÄLLFORS1, ERICH KUKK2, AND ÅKE NIEMI3
1
Finnish Institute of Marine Research, 2Institute of Botany and Ecology, University of Tartu,
Estonia, 3Tvärminne Zoological Station
Ecology and taxonomy of arcto-alpine microalgae in Tvärminne and northern
Finland
Starting in 1992, we have made extensive collections of microalgae from small water
bodies (small lakes, ponds, pools, springs, brooks, ditches and wet rock surfaces) in the
Tvärminne archipelago on one hand, and northernmost Finland (the Kilpisjärvi,
Sevettijärvi and Kuusamo areas) on the other. The algal floras of the northern and
southern regions show several remarkable similarities. The algae recorded from both
study areas include a number of rarely observed taxa such as Cosmarium hexalobum,
C. microsphinctum, C. petsamoënse, C. phaseolus v. karlukense, Staurastrum
capitulum and Staurodesmus minutissimus. The large number of arcto-alpine taxa in
the southern archipelago is at least partly explained by the abundance of extreme, i.e.
subaereal and aereal biotopes, including small rock-pools and dripping surfaces. The
surrounding sea has a levelling influence on the local climate, especially in spring and
autumn, providing extended periods of cool, non-freezing temperatures. During the
warm summer months these habitats normally dry out and force the algae to form
resting stages.
Particularly the material from the Kilpisjärvi area has yielded numerous very rare
desmids, e.g. Cosmarium caelatum f. arcticum, C. distinguendum, C. hammeri v.
croasdaleae, C. incertum v. borgei, C. pokornyanum v. groenbladii, C. quinarium v.
pictum, Euastrum dissimile v. lapponicum, Staurastrum pinguescens and some bluegreen algae, e.g. Gloeocapsa tornensis, Woronichinia botrys, W. robusta. Many of
these have been recorded only one or two times before. In the Sevettijärvi material we
have a second record of the recently described Cosmarium taxillus. In the calcareous
lakes of Kuusamo we have mainly collected blue-green algae, i.e. submerged
Scytonema alatum and the rarely recorded Pseudanabaena papillaterminata.
Two undescribed species of the blue-green algal genus Ammatoidea have been
observed in extreme biotopes. One has been found in three pools on and near the
mountain Saana in Kilpisjärvi, the other in four very small and rapidly drying
depressions on rock in Tvärminne.
Two species of the chlorococcalean genus Pseudococcomyxa have been found in the
Tvärminne area on rock surfaces kept wet by melt water runnels for prolonged times in
spring. P. tatrae was originally described from the High Tatra Mountains, and has not
since been reported from elsewhere. It is very abundant in one of our localities. The
other species is less abundant and appears to be undescribed.
52
Our observations on the morphology of the desmid Staurastrum capitulum, found in
small numbers in a rock-pool on the hill Storängsberget in Tvärminne, and in at least
two localities in the Kilpisjärvi area (altogether some 50 cells), show that the species
has been totally misinterpreted during the present century. A revision of the species
will be necessary, and related species in the section Cylindriastrum will have to be
considered as well.
Publications:
1. Kukk, E. & Hällfors, G.: A second record of Cosmarium taxillus Coesel et Delfos
(Desmidiaceae) from Finnish Lapland. − Annales Botanici Fennici (submitted).
2. Kukk, E., Hällfors, G. & Niemi, Å.: Scytonema alatum (Carmichael) Borzí
(Nostocophyceae, Nostocales) in a lake in Kuusamo, NE Finland. − Algological
Studies (submitted).
3. Kukk, E. & Hällfors, G.: Two new species of Ammatoidea W. & G. S. West
(Nostocophyceae, Oscillatoriales) from extreme biotopes in Finland. − In prep.
4. Kukk, E. & Hällfors, G.: Resurrection of the original Staurastrum capitulum sensu
de Brébisson (Chlorophyta, Desmidiaceae) on the basis of populations in
Tvärminne, SW Finland and Kilpisjärvi, Finnish Lapland. − In prep.
5. Kukk, E. & Hällfors, G.: Pseudococcomyxa lunata sp. nov. and P. tatrae comb. nov.
(Chlorophyceae, Chlorococcales), recorded from Finland; with comments on the
taxonomy of the genus. − In prep.
6. Kukk, E., Hällfors, G. & Niemi, Å.: Microalgae in pools and ponds on the Saana
mountain, Finnish Lapland. − In prep.
JAAKKO KULLBERG
Finnish Museum of Natural History, Entomology Division
The Lepidoptera fauna of islands Russarö and Örö
Russarö and Örö are situated in the outer archipelago of the northern Baltic Sea, about
5 km S and 35 km W from the city of Hanko, respectively. They are larger and more
rich in biotopes than neighbouring islands. Örö is an especially interesting island for
insect studies because it is a part of the esker chain of second Salpausselkä. The study
started in Russarö 1987 and in Örö 1990. It has been carried out mainly by using light
and sugar bait traps. The purpose of the study is to investigate which species have stable populations in the islands and compare the differences in species assemblage between islands and the mainland (sampled mainly by amateur lepidopterits in Hanko and
Dragsfjärd). Also, records of migrations, extinctions and newcomer species form one
part of the study. Örö has proved to be of national importance as a sanctuary for many
endangered species, especially those living on coastal dunes and dry meadows. As
many as 86 species of the still unpublished new Finnish red list of Lepidoptera have
been recorded in Örö. In late 1990s the most striking phenomena in archipelago has
been the newly established populations of many southern generalist and fluctuating
species. Among them have been formerly endangered species which have just revealed
to be climate dependent fluctuants. The total number of Macrolepidoptera species is
now 649 in Örö and 589 in Russarö. Also the Microlepidoptera fauna of Örö is well
studied and this far 760 species are recorded in Örö. So far, the study has produced 11
new species for the Finnish insect fauna, all are recorded in Örö: Aporophyla lutulenta
(1992), Coleophora gallipennella (1997), C. nutantella (1997), Cyclophora linearia
(1998), Cydia fagiglandana (1995), Depressaria emeritella* (1993), Dolicharthia
punctalis* (1996), Watsonalla binaria (1993), Eupithecia distinctaria (1999),
Helcystogramma lutatellum* (1999) and Syndemis histrionana* (1990). Those marked
with asterix are considered as residents.
53
JÖRGEN PALMGREN
Finnish Museum of Natural History
Monitoring birds – a selection of species
The nightjar Caprimulgus europaeus was censused in 1999 in a square of 10 x 10 km,
mainly to compare with a census carried out in 1984. The number of singing males has
not decreased in this period, but a redistribution of the pairs is expected in the near
future because a new main road is under contraction through the whole area. A new
census is planned to be done after a few years. The white-tailed sea eagle Haliaeetus
albicilla has started breeding in the vicinity causing the neighbouring two osprey pairs
to emigrate from their nests. The stress caused by sea eagle seems to be a main reason
to this. Land bird censuses carried out in twenty years as a single line-transect show on
the total scale a fairly stable population of the total number of pairs. Crossbill, willow
warbler, and wren showed greatest increases. Greatest decreasing numbers where
recorded in the numbers of wood warbler, redwing, and a little bit surprisingly tree
pipit. In recent years the forests in the census area have been modified in cuts fairly
extensively. The cormorant has continued to increase; in 1999 the number of pairs was
135 in the colony in Tammisaari, established a few years ago and which is by far the
biggest colony in Finland. The whooper swan continues to increase, now four pairs
breed in a 10x10 km square where the zoological station is situated. Of the owls the
pygmy owl has established as a breeding species in the area.
54
7. SCIENTIFIC PUBLICATIONS IN THE YEARS 1997–99
1139. Uitto, A. 1997: The role of metazooplankton grazing in the pelagial food web of the
northern Baltic Sea. – Dissert., Walter and Andrée de Nottbeck Found. Sci. Rep. 13: 1–41
+ 6 reprint.
1140. Öst, M. & Kilpi, M. 1997: A recent change in size distribution of blue mussels (Mytilus
edulis) in the western part of the Gulf of Finland. – Ann. Zool. Fennici 34: 31–36.
1141. Laurila, A. & Aho, T. 1997: Do female common frogs choose their breeding habitat to
avoid predation on tadpoles? – Oikos 78: 585–591.
1142. Laurila, A., Kujasalo, J. & Ranta, E. 1997: Different antipredator behaviour in two anuran
tadpoles: effects of predator diet. – Behav. Ecol. Sociobiol. 40: 329–336.
1143. Peuhkuri, N., Ranta, E. & Seppä, P. 1997: Size-assortative schooling in free-ranging
sticklebacks. − Ethology 103: 318–324.
1144. Hirvonen, H. & Ranta, E. 1996: Prey to predator size ratio influences foraging efficiency
of larval Aeschna juncea dragonflies. – Oecologia 106: 407–415.
1145. Hirvonen, H. & Ranta, E. 1996: Within-bout dynamics of diet choice. – Behavioral
Ecology 7: 494–500.
1146. Leskinen, E. & Pamilo, P. 1997: Evolution of the ITS sequences of ribosomal DNA in
Enteromorpha (Chlorophyceae). – Hereditas 126: 17–23.
1147. Stigzelius, J., Laine, A., Rissanen, J., Andersin, A.-B. & Ilus, E. 1997: The introduction of
Marenzelleria viridis (Polychaeta, Spionidae) into the Gulf of Finland and the Gulf of
Bothnia (northern Baltic Sea). – Ann. Zool. Fennici 34: 205–212.
1148. Uitto, A. & Hällfors, S.1997: Grazing by mesozooplankton and metazoan microplankton
on nanophytoplankton in a mesocosm experiment in the northern Baltic. – J. Plankton
Res. 19: 655–673.
1149. Uitto, A., Heiskanen, A.-S., Lignell, R., Autio, R. & Pajuniemi, R. 1997: Summer
dynamics of the coastal planktonic food web in the northern Baltic Sea. – Mar. Ecol. Prog.
Ser. 151: 27–41.
1150. Kiirikki, M. & Lehvo, A. 1997: Life strategies of filamentous algae in the northern Baltic
Proper. – Sarsia 82: 259–267.
1151. Laamanen, M. J. 1997: Environmental factors affecting the occurrence of different
morphological forms of cyanoprocaryotes in the northern Baltic Sea. – J. Plankton Res.
19: 1385–1403.
1152. Glowacka, E., Migula, P., Nuorteva, S.-L., Nuorteva, P. & Tulisalo, E. 1997: Psyllids as a
potential source of heavy metals for predators. – Arch. Environ. Contam. Toxicol. 32:
376–382.
1153. Tuomi, P. 1997: Bacterial carbon production in the northern Baltic: a comparison of
thymidine incorporation and FDC based methods. – Mar. Ecol. Prog. Ser. 153: 59–66.
1154. Walin, L. 1997: Colony characteristics and worker-queen conflicts in Myrmica ants. –
Dissert., Univ. Helsinki, Dept. Ecology and Systematics, 1–20 + 5 reprints.
1155. Olli, K. 1997: Evolutionary life-strategies of autotrophic planktonic micro-organisms in
the Baltic Sea. – Dissertationes Biologicae Universitatis Tartuensis 25: 1–65 + 6 reprints.
1156. Russell, G. & Veltkamp, C. J. 1997: Algal ecotypes: what they are and what they are not.
– Nordic J. Botany 17: 331–336.
55
1157. Laurila, A. 1997: Breeding habitat choice and larval ecology in two anurans. – Dissert.,
Univ. Helsinki, Dept. Ecology and Systematics, Div. Popul. Biol., 1–17 + 6 reprints.
1158. Peuhkuri, N. 1997: Size-assortative shoaling in three-spined sticlebacks. – Dissert., Univ.
Helsinki, Dept. Ecology and Systematics, Div. Popul. Biol., 1–18 + 6 reprints.
1159. Peuhkuri, N. 1997: Size-assortative shoaling in fish: the effect of oddity on foraging
behaviour. – Animal Behaviour 54: 271–278.
1160. Raymond, M., Vääntö, R. L., Thomas, F., Rousset, F. Meeüs, T. & Renaud, F. 1997:
Heterozygote deficiency in the mussel Mytilus edulis species complex revisited. – Mar.
Ecol. Prog. Ser. 156: 225–237.
1161. Migula, P., Glowacka, E., Nuorteva, S.-L., Nuorteva, P. & Tulisalo, E. 1997: Time-related
effects of intoxication with cadmium and mercury in the red wood ant. – Ecotoxicology 6:
307–320.
1162. Kuosa, H., Autio, R., Kuuppo, P., Setälä, O. & Tanskanen, S. 1997: Nitrogen, silicon and
zooplankton controlling the Baltic spring bloom: an experimental study. – Estuarine,
Coastal and Shelf Sci. 45:813–821.
1163. Hirvonen, H. 1997: Behavioural mechanisms of predation rate and prey choice. – Dissert.,
Univ. Helsinki, Dept. Ecology and Systematics, Div. Popul. Biol. 1–31 + 5 reprints.
1164. Ikävalko, J. 1997: Studies of nanoflagellate communities in the sea ice of the Baltic and
the Greenland Sea. – Dissert., Walter and Andrée de Nottbeck Found. Sci. Rep. 14: 1–24
+ 6 reprints.
1165. Meyer-Rochow, V. B. & Lindström, M. 1997: Light-induced photoreceptor sensitivity
loss and recovery at 4° C and 14° C in Mysis relicta Lovén (Crustacea: Percarida) from
Pojoviken Bay (Finland). – Annals Limnol. 33: 45–51.
1166. Nummelin, M., Lodenius, M. & Tulisalo, E. 1997: Water striders (Heteroptera, Gerridae)
as bioindicators of heavy metal pollution. – Entomol. Fennica 8: 185–191.
1167. Czechowski, W. & Rotkiewicz, W. 1997: Relations between Formica sanguinea Latr. and
Formica cinerea cinerea Mayr (Hymenoptera, Formicidae) – an unusual form of dulosis. –
Annales Zoologici 47: 469–478.
1168. Sundström, L. 1997: Queen acceptance and nestmate recognition in monogyne and
polygyne colonies of the ant Formica truncorum. – Anim. Behav. 53: 499–510.
1169. Keller, L., Sundström, L. & Chapuisat, M. 1997: Male reproductive success: paternity
contribution to queens and workers in Formica ants. – Behav. Ecol. Sociobiol. 41: 11–15.
1170. Lindqvist, K. & Lignell, R. 1997: Intracellular partitioning of 14CO2 in phytoplankton
during a growth season in the northern Baltic. – Mar. Ecol. Prog. Ser. 152: 41–50.
1171. Pimiä, V., Kankaanpää, H. & Kononen, K. 1997: The first observation of ocadaic acid in
Mytilus edulis from the Gulf of Finland. – Boreal Envir. Res. 2: 381–385.
1172. Thingstad, T.F. & Lignell, R. 1997: Theoretical models for the control of bacterial growth
rate, abundance and carbon demand. – Aquat. Microb. Ecol. 13: 13–27.
1173. Chapuisat, M., Sundström, L. & Keller, L. 1997: Sex-ratio regulation: the economics of
fratricide in ants. – Proc. R. Soc. Lond. B 264: 1255–1260.
1174. Leskinen, E. & Hällfors, G. 1997: Tabularia waernii (Diatomophyceae) in the northern
Baltic Sea. – Ann. Bot. Fennici 34: 141–147.
56
1175. Candolin, U. 1997: Predation risk affects courtship and attractiveness of competing
threespine stickleback males. – Behav. Ecol. Sociobiol. 41: 81–87.
1176. Kuuppo, P., Autio, R., Kuosa, H., Setälä, O. & Tanskanen, S. 1998: Nitrogen, silicate and
zooplankton control of the planktonic food-web in spring. – Estuarine, Coastal and Shelf
Science 46: 65–75.
1177. Seppälä, J., Johnsen, G., Leeben, A. & Shalapyonok, A. 1998: In vivo light absorption by
photosynthetic and photoprotective algal pigments: methodology and effects of light
acclimation and nutrient limitation. – Report Series in Geophysics 38 (Proc. 4th Finnish–
Estonian Seminar On Underwater Optics With Applications, Lammi 22–24 April 1997):
47–58.
1178. Autio, R. 1998: Response of seasonally cold-water bacterioplankton to temperature and
substrate treatments. – Estuarine, Coastal and Shelf Science 46: 465–474.
1179. Laurila, A. & Seppä, P. 1998: Multiple paternity in the common frog (Rana temporaria):
genetic evidence from tadpole kin groups. – Biol. J. Linnean Soc. 63: 221–232.
1180. Peuhkuri, N. & Seppä, P. 1998: Do three-spined sticklebacks group with kin? – Ann.
Zool. Fennici 35: 21–27.
1181. Kilpi, M. & Öst, M. 1998: Reduced availability of refuse and breeding output in a herring
gull (Larus argentatus) colony. – Ann. Zool. Fennici 35: 37–42.
1182. Öst, M. & Kilpi, M. 1998: Blue mussels Mytilus edulis in the Baltic: good news for
foraging eiders Somateria mollissima. – Wildl. Biol. 4: 81–89.
1183. Heiskanen, A.-S. 1998: Factors governing sedimentation and pelagic nutrient cycles in the
northern Baltic Sea. – Dissert., Monographs of the Boreal Envir. Res. 8: 1–80 + 9 reprints.
1184. Olli, K., Heiskanen, A.-S. & Lohikari, K. 1998: Vertical migration of autotrophic microorganisms during a vernal bloom at the coastal Baltic Sea – coexistence through niche
separation. – Hydrobiologia 363: 179–189.
1185. Katajisto, T., Viitasalo, M. & Koski, M. 1998: Seasonal occurrence and hatching of
calanoid eggs in sediments of the northern Baltic Sea. – Mar. Ecol. Prog. Ser. 163: 133–
143.
1186. Flinkman, J., Aro, E., Vuorinen, I. & Viitasalo, M. 1998: Changes in northern Baltic
zooplankton and herring nutrition from 1980s to 1990s: top-down and bottom-up
processes at work. – Mar. Ecol. Prog. Ser. 165: 127–137.
1187. Sundström L. & Ratnieks, L. W. 1998: Sex ratio conflicts, mating frequency, and queen
fitness in the ant Formica truncorum. – Behav. Ecol. 9: 116–121.
1188. Boomsma, J. J. & Sundström. L. 1998: Patterns of paternity skew in Formica ants. –
Behav. Ecol. Sociobiol. 42: 85–92.
1189. Saccheri, I., Kuussaari, M., Kankare, M., Vikman, P., Fortelius, W. & Hanski, I. 1998:
Inbreeding and extinction in a butterfly metapopulation. – Nature 392: 491–494.
1190. Heiskanen, A.-S., Haapala, J. & Gundersen, K. 1998: Sedimentation and pelagic retention
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61
8. INDEX OF CONTRIBUTORS AND THEIR E-MAIL ADDRESSES
Andersen, Tom ([email protected]) .............................................................................. 10, 12
Anderson, Donald ([email protected])................................................................................. 17
Andersson, Agneta ([email protected]) ............................................................... 14
Aro, Eero ([email protected]) ......................................................................................................... 24
Autio, Riitta ([email protected]).................................................................................... 14, 21, 23
Bäck, Saara ([email protected]) ................................................................................................... 4
Boomsma, Koos ([email protected]) ..................................................................................... 42
Boström, Christoffer ([email protected]) ....................................................................... 9
Candolin, Ulrika ([email protected]) ................................................................................... 39
Castellini, Carlo ([email protected])............................................................................ 48
Czechowski, Wojciech ([email protected]) ...................................................................... 44
Dontsov, Alexander ([email protected]) ......................................................................... 49
Ebert, Dieter ([email protected])................................................................................................ 36
Engström, Jonna ([email protected])............................................................... 21, 22, 26
Fedorovich, Irina ([email protected])......................................................................... 49
Flinkman, Juha ([email protected]) ........................................................................... 18, 21, 24, 26
Franson, Christian ([email protected]) ............................................................................. 32
Gismervik, Ingrid ([email protected]) ....................................................................... 12
Granqvist, Mikaela ([email protected]) .......................................................................... 50
Green, Sandra ([email protected]) ............................................................................. 21, 24
Haag, Christoph ([email protected]) ...................................................................... 36
Haikola, Sari ([email protected]) ....................................................................................... 46
Hakala, Tomi ([email protected])................................................................................ 21, 24
Halkka, Liisa ([email protected])................................................................................. 33, 34
Halkka, Olli ([email protected]).................................................................................... 33, 34
Hällfors, Guy ([email protected]) ........................................................................................... 52
Hannonen, Minttumaaria ([email protected]) .................................... 40, 42, 43
Hanski, Ilkka ([email protected])...................................................................................... 46
Hario, Martti ([email protected])........................................................................................ 32, 47
Heiskanen, Anna-Stiina ([email protected]) ................................................ 10, 24, 28
Helanterä, Heikki ([email protected]) .................................................................. 40, 43
Henricson, Catherine ([email protected]) ........................................................... 5, 6
Hollmén, Tuula ([email protected]) ............................................................................... 32
Hottinger, Jürgen ([email protected])................................................................................... 36
Ishikawa, Nobuyoshi ([email protected]) ........................................................... 31
Kaartokallio, Hermanni ([email protected]) .......................................................... 18
Kaitala, Seppo, ([email protected]) ................................................................................. 30
Karjalainen, Miina ([email protected]) .............................................................. 21, 24
Katajisto, Tarja ([email protected]) ........................................................................................ 21, 27
Kawamura, Toshiyuki ([email protected]) ...................................................... 31
Kiirikki, Mikko ([email protected])....................................................................................... 3
Kilpi, Mikael ([email protected]) ............................................................................ 8, 32, 33, 46
Kivi, Kai ........................................................................................................................................ 14
62
Koho, Jorma ([email protected]) ........................................................................................50
Kokkonen, Marjaana ......................................................................................................................22
Korpinen, Samuli ([email protected])...........................................................................7
Koski, Marja ([email protected]) ...........................................................................21, 22, 24
Kremp, Anke ([email protected]).................................................................................17, 18
Kukk, Erich ....................................................................................................................................52
Kullberg, Jaakko ([email protected])...........................................................................53
Kuosa, Harri ([email protected]) ...............................................................................14, 18, 21, 22, 26
Kuuppo, Pirjo ([email protected])...............................................................................10, 12, 14
Lahdes, Eila ([email protected]) ................................................................................................48
Lahtinen, Markku ([email protected]) ......................................................................38
Lehtonen, Jukka T. ([email protected]) ........................................................................8
Lehtoranta, Jouni ([email protected]).................................................................................28
Leppäranta, Matti ([email protected]).........................................................................31
Lignell, Risto ([email protected])...........................................................................10, 12, 14
Lindfors, Antti ([email protected]).............................................................................30, 31
Lindström, Kai ([email protected]) .................................................................................37
Lindström, Magnus ([email protected]).......................................................29, 48, 49
Mattila, Johanna ([email protected]).....................................................................................9
Munsterhjelm, Riggert ([email protected]) .......................................................5, 6
Mustonen, Olli ([email protected]) ...................................................................................8
Niemi, Åke ([email protected])..........................................................................................52
Ojala, Petri ([email protected])...............................................................................................5
Ostrovsky, Michail ([email protected]) ........................................................................49
Pajunen, Ilmari ([email protected]) .........................................................................32, 36
Pajunen, Irmeli ([email protected]) ...............................................................................32
Palmgren, Jörgen ([email protected]).........................................................................54
Pekuri, Sanna ([email protected]) ....................................................................................17
Pertola, Sari ([email protected])..........................................................................................22
Raateoja, Mika ([email protected]).......................................................................................16
Rasmus, Kai ([email protected])..........................................................................................31
Rautio, Milla ([email protected]) .......................................................................................26
Reinikainen, Marko ([email protected])..................................................................22
Reitalu, Triin ([email protected]).................................................................................................4
Repka, Sari ([email protected]).............................................................................................22
Rosenberg, Mirja ([email protected]) .......................................................................21, 22, 24
Roslin, Tomas ([email protected]) ....................................................................................34
Roukka, Kaisa ..........................................................................................................................33, 34
Russell, George ................................................................................................................................3
Ruuskanen, Ari ([email protected]) ..............................................................................3, 4
Samuelsson, Kristina ([email protected]) ........................................................14
Sandberg-Kilpi, Eva ([email protected]) .....................................................................5, 50
Schmidt, Katrin ([email protected]) ...............................................................22
Seppälä, Jukka ([email protected]) ......................................................................10, 12, 14–16
63
Setälä, Outi ([email protected]) ............................................................................................ 10, 19
Setälä, Vienna ([email protected]) .................................................................................. 44
Shirasawa, Kunio ([email protected]) ............................................................... 31
Sillanpää, Heidi ([email protected]) ............................................................................................. 9
Sivonen, Kaarina ([email protected]).......................................................................... 22
Sjölund, Ulla ([email protected]) ...................................................................................... 22
Stevens, Paul ([email protected]) ..................................................................................... 40
Stipa, Tapani ([email protected])............................................................................................. 29
Sundström, Liselotte ([email protected])......................................................... 40–44
Takizawa, Atsushi ([email protected]) ................................................................. 31
Tamminen, Timo ([email protected])..................................................................... 10, 12, 14
Tanskanen, Sanna ([email protected]) ....................................................................... 23
Tiribilli, Bruno ([email protected]) ............................................................................................. 48
Trontti, Kalevi ([email protected]) ...................................................................... 40, 42, 43
Tuomi, Pirjo ([email protected]) ......................................................................................... 10, 12
Ugolini, Alberto ([email protected]) .............................................................................. 48
Uitto, Anna ([email protected])............................................................................................ 14
Vainio, Liisa ([email protected]).......................................................................................... 48
Vakkari, Pekka ([email protected]) ............................................................................... 35
Viherluoto, Maiju ([email protected]) ........................................................... 21, 24, 26
Viitasalo, Markku ([email protected])............................................... 21–24, 26, 27, 38
Voigt, Heinz-Rudolf ([email protected]) ................................................................ 51
Vuorinen, Ilppo ([email protected]) ............................................................................... 21, 24
Westerbom, Mats ([email protected]) .......................................................................... 8
Öst, Markus ([email protected]) ............................................................................. 32, 46, 47
64