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Monitoring changes in North Atlantic
plankton communities
Background
The North Atlantic is the largest
oceanic water mass associated
with Europe and thus a key area
for the EUR-OCEANS network.
The outcome of many nationallyfunded research programmes over
the last decade had been the realisation that human impacts (e.g.
climate change, species introductions) apply across the North Atlantic basin, thus requiring the cohesive and coordinated research
promoted by EUR-OCEANS. This
Fact Sheet introduces some of the
conclusions regarding possible human induced changes in the North
East Atlantic planktonic communities over the last 50 years.
Climate change
Long-term variations in plankton abundance in the North Atlantic ecosystem have been
investigated by the Continuous Plankton Recorder survey (CPR) since 1946 as well as
at several fixed coastal monitoring stations.
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Black dots show zooplankton sampling sites
in the North Atlantic,
background shows SeaWiFS satellite chlorophyll
distribution.
Map: Todd O’Brien,
NMFS-COPEPOD, USA.
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These conclusions are based on
long-term plankton records which
are valuable for documenting ecosystem changes, for helping to
separate natural and anthropogenic changes, and for generating
and analyzing testable hypotheses. Over the last decade, interest
in long-term plankton sampling
has increased.
However, long
time-series are still uncommon.
The purpose of long-term monitoring is to establish a baseline
for the various components of the
ecosystem, and how they interact.
Information can be used to:
• distinguish between the effects
of human activities and natural
variability
• define baselines and estimate
the recovery time of the system
after human or environmental
perturbations
• develop hypotheses about causal relationships which can then be
investigated
• verify and validate models used
to predict changes in marine ecosystems on the basis of climate
scenarios, and
• evaluate management actions.
June 2006
30 N
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Studies show that key mechanisms link environmental forcing and plankton response
i.e. timing and intensity of the
spring phytoplankton bloom
resulting from changes in
stratification levels, changes
in temperature, and, in the
case of the copepod Calanus
finmarchicus, advection of the
population into the North Sea
at the end of the winter season.
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Cold-temperate
mixed-water species
1951-1981
0
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Subarctic
species
Warm-temperate
pseudo-oceanic species
1951-1981
1951-1981
Temperate
pseudo-oceanic species
1951-1981
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1982-1999
1982-1999
1982-1999
1982-1999
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2000-2002
2000-2002
2000-2002
0.0 0.2 0.4 0.6 0.8 1.0
0.0 0.2 0.4 0.6 0.8 1.0
0.0 0.2 0.4 0.6 0.8 1.0
2000-2002
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50 N
0.0 0.2 0.4 0.6 0.8 1.0
The NE Atlantic has warmed
Mean number of species per CPR sample
2-3 C over the last 50 years.
Changes in the mean number of copepod species from 1951-2002,
showing northward extension of warm water species and northward reThis has resulted in a northtreat of cold water species. Recalculated after Beaugrand et al., 2002.
wards shift (of approximately
1000km) in warm water plankton communities. There has also been a decrease in the
key copepod Calanus finmarchicus and an increase Calanus helgolandicus. Such a
shift could impact on the whole ecosystem, for example larval/juvenile cod feed on C.
finmarchicus, its replacement by C. helgolandicus may therefore have a detrimental
effect on their overall viability because both species are abundant at different times of
the year. Such changes may have exacerbated the impact of over-fishing in reducing
recruitment of North Sea cod since the mid-1980s.
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Fact Sheet 4
Long-term plankton monitoring and non-indigenous species
The introduction of non-indigenous marine plankton species can
have a considerable ecological and economic effect on regional systems. For example the introduction of the ‘comb jelly’ (Mnemiopsis
leidyi) to the Black Sea is known to have had dramatic consequences
on the food web. The main pathway for invasive species introduction
is via ship ballast waters. There has been increasing concern about
the apparent increase in species introductions worldwide, but their
presence can go unnoticed until they reach nuisance status. As a
consequence there are few case-histories providing information on
their initial appearance and their spatio-temporal patterns.
Since the 1980’s phytoplankton biomass has increased in the North
Sea. How much of this increase can be attributed to the introduced
phytoplankton species Coscinodiscus wailesii is yet to be determined. There is however, already strong evidence to suggest that
under certain conditions C. wailesii can displace indigenous plankton species. As many native phytoplankton feeders find the species
unpalatable, its dominance can have detrimental effect on the food
web. Such shifts in ecology of the North Sea need to be monitored by
sustained long-term observations. The case of C. wailesii is the first
of its kind to show the spatial evolution of an invasive phytoplankton
species over a decadal period and highlights the need for continuous
monitoring to assess the effectiveness of any management strategy
put in place to limit invasions.
For more details: Sir Alister Hardy Foundation for Ocean
Science (SAHFOS) www.sahfos.org
Abundance estimates, based on CPR monitoring, of
Coscinodiscus wailesii in the North East Atlantic between
1985-1995. Image: Martin Edwards, SAHFOS, UK.
Picture of C. wailesii from sample taken off Plymouth in
March 2000. Notice the size of the species in comparison
to the copepod and the almost mono-specific nature of the
sample. Photograph: Karl Embelton, SAHFOS, UK.
Conclusions and Action points
• The plankton community in the NE Atlantic and the North Sea are changing as a consequence of climate
change and species introductions.
• Long-term monitoring plankton programmes in the North Atlantic are essential to evaluate the consequences
of these changes.
• EUR-OCEANS considers that monitoring is essential to determine whether the climate-plankton connections observed
during several decades will persist in the future or will be overruled by other mechanisms and principally humaninduced impacts.
• EUR-OCEANS support:
- the development of effective international mechanisms for sharing plankton monitoring data
- optimising the control of ballast waters
- implementing an ecosystem approach to fisheries management by taking into account changes in plankton biodiversity.
This fact sheet was jointly composed by scientists involved in the ICES Working Group on Zooplankton
Ecology as well as colleagues from The Sir Alister Hardy Foundation for Ocean Science in Plymouth, UK.
For further information please contact Luis Valdes ([email protected]), Martin Edwards (maed@sahfos.
ac.uk) or Delphine Bonnet ([email protected]). For the ICES Zooplankton Status Report go to http://www.
ices.dk/products/cooperative.asp
Fact Sheet by: EUR-OCEANS Knowledge Transfer Unit, hosted by the GLOBEC IPO at Plymouth Marine Laboratory.
For further information contact, Jessica Heard: [email protected] or visit the Website: www.eur-oceans.org/KTU