Plankton

FRS; SAHFOS

WHAT IS ALREADY HAPPENING	WHAT COULD HAPPEN
A 1,000-km northward shift of warmer-water plankton, with a similar retreat of colder-water plankton, has been observed in the north-east Atlantic over the past 50 years, as the seas around the UK have become warmer. In the North Sea, the population of the previously dominant and important cold-water zooplankton species Calanus finmarchicus has declined in biomass by 70% since the 1960s. The seasonal timing of plankton production has altered in response to recent climate changes. Some species are occurring up to four to six weeks earlier than 20 years ago, affecting predators, including fish.	Continued increase in sea temperature, due to climate change and associated changes such as ocean acidification, are likely to exert major influences on plankton abundance and geographical distributions, with implications for primary production and climate control.

WHAT IS ALREADY HAPPENING

WHAT COULD HAPPEN

A 1,000-km northward shift of warmer-water plankton, with a similar retreat of colder-water plankton, has been observed in the north-east Atlantic over the past 50 years, as the seas around the UK have become warmer.
In the North Sea, the population of the previously dominant and important cold-water zooplankton species Calanus finmarchicus has declined in biomass by 70% since the 1960s.
The seasonal timing of plankton production has altered in response to recent climate changes. Some species are occurring up to four to six weeks earlier than 20 years ago, affecting predators, including fish.

Continued increase in sea temperature, due to climate change and associated changes such as ocean acidification, are likely to exert major influences on plankton abundance and geographical distributions, with implications for primary production and climate control.

Executive summary

Major changes have taken place in both the plant (phyto-) and animal (zoo-) plankton of the seas around the British Isles over the last few decades. They include:

The important decadal climate indicator for the North Atlantic, the NAO, has been rising along with Northern Hemisphere Temperatures over the past 30 years and the surface waters of the European Continental shelf have been warming. This has caused extensive changes in the planktonic ecosystem in terms of plankton production, biodiversity and species distribution which has had effects on fisheries production and other marine life (e.g. seabirds) (Reid & Edwards, 2001; Edwards et al, 2001, 2002; Beaugrand et al, 2003, 2004; Richardson & Schoeman, 2004; Southward et al, 2004; Alheit et al, 2005; Heath, 2005) .
In the North Sea the population of the previously dominant and important zooplanktonPlanktonic marine animals. Click for link to the SAHFOS Marine Climate Change Encyclopaedia species, (the cold water species Calanus finmarchicus) has declined in biomass by 70% since the 1960s. Species with warmer-water affinities are moving northward to replace the species but are not numerically as abundant (Beaugrand et al, 2004; Edwards et al, 2007).
There has been a northward shift in the distribution of many plankton and fish species by more than 10o latitude (over 1000km) over the past fifty years. This shift is particularly associated with the shelf edge current running north along the European continental margin (Beaugrand et al, 2002; Brander et al, 2003; Genner et al, 2004).
The seasonal timing of plankton production also altered in response to recent climate changes. Some species are occurring up to four to six weeks earlier than 20 years ago. This has consequences for plankton predator species, including fish, whose life cycles are timed in order to make use of seasonal production of particular prey species (Edwardss & Richardson, 2004).
The decline of the European cod stocks due to overfishing has been exacerbated by climate induced changes in plankton production. The survival of young cod in the North Sea appears to depend on the abundance, seasonal timing and size composition of their planktonic prey. As the stocks declined they have become more sensitive to the effects of regional climate warming due to shrinkage of the age distribution and geographic extent (Brander, 2005).
Future warming is likely to alter the geographical distribution of primary and secondary In the water columnpelagic production, affecting ecosystem services such as oxygen production, carbon Technical method of removing CO2 from the atmosphere into another form for storage. sequestration and Are cycles that transfer energy and chemicals around marine ecosystems through life (bio) and its environment (geo).biogeochemical cycling. These changes may place additional stress on already-depleted fish stocks as well as have consequences for mammal and seabird populations.

Full scientific review (with references)

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Confidence assessments

What is happening now - Medium

What could happen in the future - Low

There is a medium to high level of confidence in what is happening to the plankton now based on information from the CPRDeveloped by Sir Alister Hardy the Continuous Plankton Recorder (CPR) is a towed instrument that takes continuous samples of plankton in the ocean surface, on sections that span ocean basins. CPR surveys have been in operation for 75 years and now form a long, rich and valuable time-series of observations in the many marine ecosystems. See www.sahfos.ac.uk survey and corroborated through smaller-scale surveys and satellite observations. For example, changes in the biogeography and phenology of plankton are highly significantly correlated with Northern Hemisphere Temperature changes. We are less (medium to low) confident of future scenarios.

Knowledge gaps

Understanding and predicting rapid and abrupt ecosystem shifts.
Mechanistic links between climate warming, plankton and fisheries to form a predictive capacity.
Understanding the rate of genetic adaptation to climate change impacts.
Identifying species or communities particularly vulnerable to climate change impacts.
Understanding the processes involved in the biological pump and quantifying its global spatial and temporal variability.
Determining the mechanisms behind observed temperature increases off the continental margins of Europe including advectiveIn the sea processes that are advective can be simply thought of as those that transport a property (eg heat, salinity) of, or substance (eg. plankton, pollutant) in, the water by the movement of the water from one place to another. processes and their effect on Northern European Seas.
Filling major gaps in the coverage of In the water columnpelagic and biochemical measurements in the global oceans in particular the Arctic Oceans and Nordic Seas.

Commercial impacts

The changes in the plankton have had a major impact on commercial fish stocks and the general carrying capacity and health of marine ecosystems. For example, the decline in gadoid biomass, especially cod has been linked with plankton, and can also explain the marked reduction in returns of salmon to home waters (Beaugrand et al, 2003; Beaugrand & Reid, 2003). A climate link has also been established between plankton, sandeels and seabirds (Frederiksen et al, 2006).

Authors

Martin Edwards and Chris Reid
Sir Alister Hardy Foundation for Ocean Science, The Laboratory, Citadel Hill, Plymouth, PL1 2PB.

Mike Heath
Fisheries Research Services Marine Laboratory, PO Box 101, 375 Victoria Road, Torry, Aberdeen, UK, AB11 9DB

Regional consultation and comparison: Sarah Hughes & Eileen Bresnan (Scottish regional areas), Fisheries Research Services Marine Laboratory. Gerald Boalch & David Conway (English Channel regional area), Marine Biological Association of the UK. Wulf Greve (South-eastern North Sea regional area). German Centre for Marine Biodiversity Research, Senckenberg Research Institute, Hamburg, Germany.