Download Algae censors biodiversity formation in the North Russian rivers

Algae censors biodiversity
formation in the North Russian
rivers
Sergei Komulainen
Institute of Biology, Karelian Research Centre, Russian Academy of Sciences
Pushkinskaya 11, 185610 Petrozavodsk, Republic of Karelia, Russia
Introduction
Lists of species provide the basis for the study of the biota structure and the factors that
affect it. It is important to make systematic analysis more complete, but it is equally
important to improve diagnoses, to revise classifications and phylogenetic schemes,
and to change the concept of a species. Besides, one should bear in mind that species are
not equivalent in their “contribution” to biota structure. They can differ in evolution
status, the extent of phylogenetic isolation, and functional role in ecosystems. Therefore, assessment of diversity solely as an arithmetic sum of species without considering the fact that they are not equivalent is hardly acceptable, and does not reflect
changes in a coenoses.
Changes in the species number and its relatively abundance in periphyton communities can be used to survey water quality. Many richness, evenness and diversity
indices have been developed to characterize communities. But more often have been
suggested that the best means for detecting shift in the environment is Shannon-Weaver diversity index, which is an integral characteristic of assemblages.
The purpose of this paper is to summarize and discuss, with specific examples, the
variations in species diversity not only after changes in abiotic factors, but also in
watercourses that differ in geographic position. The hypothesis that changes in species
diversity can be used as an indicator of changes in water quality was tested
Material and methods
Attached communities have been studied at 49 streams located within north-western
Russia from Ladoga Lake to Barents Sea. It allows to estimate the climatic and the
hydrological regime influence on phytoperiphyton communities structure and abundance.
Biodiversity indices have been tested with materials collected from natural and
artificial substrata. In all the rivers studied, samples were collected during a short summer low-water period. In some rivers characteristic of each region observation was
conducted during an open water period (April-October) or rivers were studied throughout the season.
The sample form of Shannon-Wiever formula
H =−
( N i / N ) ln( N i / N )
was used as an index of species diversity. It was calculated separately for diatoms and
for communities in whole, for rivers and separate locations and communities. The
diatom database software “OMNIDIA” (Lecointe et al. 1993) was used to calculate
trophic diatom index (TDI), the values of which varied more at low concentrations
(Eloranta 1999).
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The Finnish Environment 485
Results and discussion
The most important characteristics of the phytoperiphyton in studied rivers is underline its belonging to the flora of boreal type, as true high latitude elements even in the
rivers of the Barents Sea Basin occupy, as a rule, a subordinate position (Komulainen
2002). Taxonomic structure of periphyton displays a tendency for the concentration of
inter- and intraspecies taxons in a small number of genera and families while at the
same time forming a considerable amount of genera and families comprised of few
species which reflects the complexity of florogenetic processes. This trend suggests
that a significant role in the formation of periphyton, in studied rivers is played by the
allochthonous way of development.
Taxonomical structure of algal communities is formed either due to the introduction of new taxons into them or at the expense of combinatorial change within the
same species. The first is determined for periphyton by entering of allochthonic species
from plankton and bottom algae communities. Floristic diversity is also maintained
due to the succession asynchronism in various sites of the river system and algal drift
explains simultaneous presence of spring, summer and autumn species in algocenosis
at that, the formation rate is mainly regulated by light conditions.
Some “northern” traits, characteristic of algal periphyton flora, are apparent at the
different levels of taxonomic analysis (Komulainen 1998). With predominance of
diatoms, blue-green algae become less diverse northwards than green algae. Species
that show a high phosphorus and nitrogen demand are the first to drop out of algal
coenoses. Forms that are accidental for the periphyton are less common than true attached forms. Nostocales/Oscillatoriales ratio increases from 1.6 for the rivers of the Ladoga Lake basin to 4.0 for those of the Barents Sea basin.
Assessing the impact of climate changes on biodiversity is difficult due to the
spatial and temporal scale and the complexity of the problem, and its interactions with
other environmental factors. In spite of marked north-south variations in taxonomic
composition of phytoperiphyton in study rivers, the diversity indices values remain
practically the same ranged from 2.0 to 3.0 for most rivers (Fig. 1). This shows that the
algal coenoses of periphyton are highly developed in the rivers studied that have high
vital activity, self-regulation and stability.
Fig. 1. Correlation between river location (latitude) and phytoperiphyton species diversity indices
(H).
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At the same time the heterogeneity of habitat in each river is very high and significant
for the formation of periphyton diversity. Firstly differences in species composition
have been observed between pool, run and riffle habitats. Current is the main “taking”
factor determining mosaic character of the periphyton communities distribution and
regulating the periphyton succession. It is noted that during floods, a large quantity of
attached material is irretrievably removed from the ecosystem, and the formation of
biodiversity begins from the very beginning.
Species diversity peaked quickly during colonisation and decreased as the length
of exposure increased. Pool zone showed greater diversity indices during the first few
days exposure than did slides exposed in riffle zones. After week diversity of algaecoenoses was significantly (p<0.05) greater at 0.1 m c-2 than at 1.0 m c-2. Later on this
brief conditioning period, however, the riffle slides showed more rapid cell growth and
accommodation rates, particularly. That is why in the rapids with poorly sorted mosscovered rocky substrates diversity values were generally greater than at the pools. But
for both cases the negative relations of an index Shannon-Wiever with phytoperiphyton
biomass was very weak (r = 0.30, F = 3.50, P < 007).
Besides, phytoperiphyton diversity was observed to increase in rivers with large
basin areas (Fig.2) and decreased in communities were filamentous algae have become
very abundant.
Fig. 2. Correlation between river size (length, km) and phytoperiphyton species diversity indices
(H).
Variations in diversity are caused not only by the variability of hydrological regime.
Lake factor is of great importance, by the removal of allochthonous species from swamps
and running-water lakes (Komulainen 1999). Structure and abundance of allochthonic
algae flora changes in dependence on the number of lake their morphometry, trophic
status and seasons. In attached communities, in addition to euperiphytonic forms, which
have adjusted to the attached mode of life and are scarce in other algocenotic types,
periphyton was found to include planktonic and benthic algae. Allochthonous forms
are clearly dominated by colony-forming planktonic diatoms, such as Aulacosira spp,
Melosira spp, Fragilaria spp. and Tabellaria fenestrata (Lyngb.) Kütz. A particularly substantial contribution to the formation of periphyton in large lakes is sometimes made
by planktonic green (Palmodictyon viride Kütz., Hyalotheca mucosa ( Merth.) Ehr. )
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The Finnish Environment 485
and the blue-green (Gloeotrichia echinulata (J. S. Smith.) P. Richt., Microcystis aeruginosa
Kütz., Aphanizomenon flos-aquae (L.) Ralfs, Anabaena spp., Woronichinia naegeliana (Ung.)
Elenk., and Oscillatoria agardhii (Gom. )) algae, that cause waters “blooming”.
Migration of a large number of algae from one assemblage to another and from
lakes to rivers leads to significant indices of diversity changes, which constant fluctuations indicate the low organization and stability of algal communities in these locations. As a result of such “mutual enrichment” the classical continuum has been interrupted and local increase/decrease changes in phytoperiphyton communities diversity
constantly observed .
Most of the rivers are not affected by human activities. The impact of man on the
water bodies is basically caused by the discharge of domestic and agricultural waste
water rich in nutrients. The increase of anthropogenic effect leads to slightly increased
bottom species diversity and structural trivialization, followed by a decline in the number
of dominant species. The halophobic-acidophilic-indifferent composition of diatoms is
enriched in alkaliphilic and halophilic species. Leading oxiphilic xenosaprobic diatoms
of the genera are observed to drop out, and the role of Tabellaria becomes less important. TDI values calculated for river in which same human impact was observed varied
rather widely but correlation between the TDI and index of biodiversity was significant (r=0.46; F=19.0; P<00004).
There are problems with using species diversity indices to indicate pollution trend
to be related to predicting decrease in diversity in response to decrease in water quality. But in our experiments with artificial substrates it has been found that at the initial
stages of contamination, the structure changes by introduction of new species and the
large-scale reproduction of the species that were earlier scarce in phytocenosis. Fig.
There are changes in diversity index for periphyton communities in Lizma River developed on slides which were placed to points where there was sewage water input in
river, after three months exposure in clear water (Fig. 3). With an increase in anthropogenic impact an oligodominant complex of species is formed and structural trivialization followed by a decline in the number of dominant species and the communities
become less diverse and structurally more simple.
Fig. 3. Box plot of species diversity indices (H) for phytoperiphyton developed in point of sewage
water input.
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173
The minimisation of anthropogenic effect and the stabilization of hydrological
regime lead to the rapid reconstruction of the natural structure of algal cenosis. It has
often been noticed that algal flora has a natural structure even at a short distance from
the place of wastewater discharge. This is favoured by alternation of zones differing in
hydrological regime, when a riffle-pool complex acts as “a natural water treatment
facility”.
References
Eloranta P. 1997. Application of diatom indices in Finnish rivers. - 3rd European Workshop “Use of
algae for monitoring rivers”. France: 138-144.
Komulainen S. 1998. Climate changes and some peculiarities of periphyton development in streams - Climate and waters. Helsinki. Finland: 527-532
Komulainen S. 1999. The influence of lake on algal communities structure and dynamics in lake-river systems.- Proceeding of 8th International Conference on Conservation and Management of Lakes. Copenhagen. Denmark. S12C-2
Komulainen S. 2002. Features in periphyton in some rirers of northwestern Russia. -Verh. Intern.
Verein. Limnol. 27: 3159-3161.
Lecointe C, Coste M & Bukowska J. 1993. “Omnidia”: software for taxonomy, calculation of
diatom indices and inventories management. - Hydrobiologia 269/270: 509-513.
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The Finnish Environment 485