Download Marine plankton - Scottish Natural Heritage

Scottish Natural Heritage
BIODIVERSITY INDICATOR
S014 – December 2011
Marine Plankton
Plankton, both plant (phyto-) and animal (zoo-) are at the lowest levels
of the marine ecosystem. They are a vital food-source for higher-level
organisms and so form the base of the marine food web. Generally
plankton have a rapid lifecycle, producing several generations per
year and are therefore more likely to show any impacts of climate
change before higher trophic organisms such as fish or crabs. There
is strong evidence that plankton communities have responded to
warming waters around the UK, both in their distribution, and the
timing of their peak occurrence through the year.
Calanus finmarchicus ©SAHFOS
© SAHFOS
Evidence
Data from the Sir Alister Hardy Foundation for Ocean Science, which runs the Continuous Plankton
Recorder (CPR), are presented here for Scotland. Phytoplankton Colour Index (PCI) is a measure of
phytoplankton biomass and therefore primary production. Two common species of copepod (small
crustaceans) were also examined, Calanus helgolandicus and Calanus finmarchicus. These species
are indicative of prevailing conditions – C. helgolandicus favours warmer (temperate) waters, and C.
finmarchicus is more frequently found in colder (boreal) waters. Calanus species in general are an
important food source for fish and the total abundance of Calanus is also presented.
Change in plankton abundance, 1958 to 2010
Continuous plankton recorder results (SAHFOS)
500
Index (1958-1967 = 100)
400
Phytoplankton Colour Index
C. finmarchicus
C. helgolandicus
Total Calanus
300
``
200
100
0
1958
1968
1978
1988
1998
2008
Year
Assessment
 Phytoplankton abundance increased within the assessed period and was 141% of the
baseline in 2010.
 C. finmarchicus, a cooler water species, declined in abundance to 33% of the baseline in
2010.
 C. helgolandicus, a warm water species, increased in abundance to 363% of its baseline.
 Total Calanus (all species combined) abundance declined from the mid-1960s despite the
increase in C. helgolandicus, but in recent years abundance has returned to 91% of the
baseline.
TREND
Divergent
DATA CONFIDENCE
http://www.snh.gov.uk/indicators/
High
Commentary
The CPR survey has run for 80 years, with unchanged methodology since 1958. This allowed the
study of long-term changes in the plankton community. During this period, the evidence for climate
change (or global warming) has increased; over the last 25 years, coastal sea temperatures around
Scotland have risen by 0.5 to 1.5oC (Sparks et al., 2006).
Phytoplankton form the base of the marine food web – increased phytoplankton biomass (in this case
represented by PCI) may stimulate greater productivity at higher trophic levels. However, an increase
in phytoplankton biomass may be due to a greater abundance of phytoplankton species which are not
eaten by existing herbivores, or because of an increase in potentially detrimental species which can
form harmful algal blooms (HABs). One hypothesis is that the increase in PCI is due to increased
nutrient loads or eutrophication. Whilst this may be likely in coastal or sheltered regions, results from
the CPR survey point to a link between changes in phytoplankton (particularly HAB taxa) and regional
climate change, in particular temperature, salinity and large scale atmospheric fluctuations (Edwards
et al., 2006).
Changes in the abundance of Calanus finmarchicus and C. helgolandicus, have been reported by
Beaugrand et al. (2003), Edwards et al. (2005) and many others, with a strong link between changes
in these species and warming seas. Recent work by Beaugrand (2012) has shown that the thermal
regime of the North Sea has changed, with a northward movement of a critical thermal boundary (the
annual 9oC to 10oC isotherm), causing an ecosystem shift. This has resulted in a decline in C.
finmarchicus and an increase in C. helgolandicus.
During the 2000s C. helgolandicus became almost as abundant as C. finmarchicus was in the 1960s,
with only a slight decrease in overall Calanus numbers. However, C. helgolandicus is known to have
a lower biomass value than C. finmarchicus, meaning that potentially there is less food (energy) for
higher trophic levels, such as fish. In addition, Thackeray et al. (2010) identified a change in the
seasonal timing of the annual bloom pattern of some plankton groups (see Scott et al., 2011), with
potential consequences at critical stages in the life cycles of species, potentially causing a mismatch
between predators (fish) and prey (zooplankton).
Source data and updates
Data were provided by the Sir Alister Hardy Foundation for Ocean Science, Plymouth, United
Kingdom. The Continuous Plankton Recorder survey has been collecting data in the North Atlantic
and North Sea since 1931, monitoring the near-surface plankton species composition and abundance
on a monthly basis. Data are obtained from a plankton sampling instrument towed from merchant
ships on their normal sailings. This indicator is updated annually. For specialist advice contact: D.
Johns, The Sir Alister Hardy Foundation for Ocean Science (SAHFOS). http://www.sahfos.ac.uk/
UK Indicators
The Scotland indicator has no current UK equivalent.
References
Beaugrand, G. 2012. Unanticipated biological changes and global warming. Marine Ecology Progress
Series, 445, 293-301.
Beaugrand G., Brander K.M., Lindley J.A., Souissi S. & Reid P.C. 2003. Plankton effect on cod
recruitment in the North Sea. Nature, 426, 661-664.
Edwards, M., Licandro P., John A.W.G. & Johns D.G. 2005. Ecological Status Report: results from
the CPR survey 2003/2004. SAHFOS Technical Report, No. 2. ISSN 1744-075.
Edwards, M., Johns, D.G., Leterme, S.C., Svendsen, E. and Richardson, A.J. 2006. Regional
climate change and harmful algal blooms in the northeast Atlantic. Limnology and Oceanography,
51, 820-829.
Scott, B., Stead, S.M. and Marrs, S.J. 2011. Changes to Scotland’s surrounding seas. In The
Changing Nature of Scotland, ed. by S.J. Marrs, S. Foster, C. Hendrie, E.C. Mackey, D.B.A.
Thompson. TSO Scotland, Edinburgh, pp153-166.
Sparks, T.H., Collinson, N., Crick, H. et al. 2006. Natural Heritage Trends of Scotland: phenological
indicators of climate change. Scottish Natural Heritage Commissioned Report No. 167.
Thackeray, S., Sparks, T., Frederiksen, M. et al. 2010. Trophic level imbalances in rates of
phenological change for marine, freshwater and terrestrial environments. Global Change Biology, 16,
304-313.
http://www.snh.gov.uk/indicators/