This report is a contribution to the Strategic Environmental Assessment (SEA4) conducted by the Department of Trade and Industry. The plankton community in the SEA4 area is similar to that in the North Sea, with variations in the abundances of some individual species. Emphasis in this review is put on trends in the abundances of major phytoplankton and zooplankton taxa over the last 40 years. The study is based on a unique long-term dataset of plankton abundance in the North Atlantic and the North Sea acquired by the Continuous Plankton Recorder (CPR). In the phytoplankton community, conspicuous trends are the steady increase in Phytoplankton Colour (an indicator of phytoplankton biomass) since 1960 and the mid 1980s peak in Thalassiosira spp. abundance. Among the zooplankton the decline in the abundance of Calanus finmarchicus and the increase in that of Calanus helgolandicus since 1960 are probably related to increasing sea surface temperatures in the northeast Atlantic. Phytoplankton blooms are discussed, from the normal annual blooms to harmful algal blooms (HABs). Because of the extensive fish farm industry in coastal regions of SEA4, there is considerable interest and ongoing research into HABs, but there is no clear evidence that they are increasing in frequency or intensity due to anthropogenic eutrophication. Other important components of the plankton meroplankton, picoplankton and megaplankton are also reviewed.

This report is a contribution to the Strategic Environmental Assessment (SEA3) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change) and has been written as an addendum to the more comprehensive SEA2 document. The two papers give an overview of the phytoplankton and zooplankton community composition in the North Sea and how this has fluctuated through the latter half of the 20th Century in response to environmental change. The study is based on a unique long-term dataset of plankton abundance in the North Atlantic and the North Sea acquired by the Continuous Plankton Recorder (CPR). The dinoflagellate genus Ceratium dominates the phytoplankton community in the North Sea, but diatoms are also important, especially in the southern part. The normal annual blooms of plankton are discussed, as are harmful algal blooms (HABs), which appear to be on the increase, possibly due to a combination of climatic variability and eutrophication. Among the zooplankton, copepods are particularly important and constitute a major food resource for many commercial fish species, such as cod and herring. Calanus is the dominant copepod genus in the North Atlantic. Other important components of the plankton - meroplankton, picoplankton and megaplankton - are also reviewed. Very small picoplankton (~1 micron in diameter) and much larger gelatinous members of the megaplankton (e.g. jellyfish and ctenophores) are poorly sampled by the CPR. Although the picoplankton represents a sizeable fraction of total primary production, its role in the marine ecosystem is poorly understood.

This report is a contribution to the Strategic Environmental Assessment (SEA7) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). The purpose of this report was to provide an assessment of the plankton ecology for SEA7. Owing to the size of the area being assessed this report divides the region into two sections. The basis of this division follows the 200m depth contour generally accepted as being the boundary between the shelf edge and oceanic realms. The first section being waters found on the continental shelf and are therefore more prone to freshwater runoff from land and anthropogenic inputs. The second section represents waters off the shelf edge, these waters are of a more oceanic origin and are less impacted by inputs from land-based sources. Information on the nutrient biogeochemistry (nitrate, phosphate and silicate) are presented for three geographical provinces, the oceanic and shelf edge realms outlined above and also for the Clyde Sea area this being a region noted as having elevated nutrient loadings from anthropogenic sources.

This report is a contribution to the Strategic Environmental Assessment (SEA6) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). This report summarises information on the ecology of planktonic species found in the SEA6 area. The Irish Sea is very diverse not only in the physical-chemical regimes operating upon it, but in the ecology of planktonic organisms found there. Data on the nutrient chemistry of the Irish Sea shows that the eastern Irish Sea is more heavily impacted by nutrients owing to freshwater run-off from land, which is far greater than in the western Irish Sea. Nutrients increased from the 1950's to the 1980's after which time the concentrations have levelled off and in some case declined. The phytoplankton biomass appears to have mirrored the influence of the nutrients both in time and space. Highest biomass (inferred from chlorophyll analysis) is generally found in regions of low salinity and tends to be greatest in the eastern Irish Sea. The phytoplankton community has also been shown to vary throughout the seasons and also within different regions or 'ecohydrodynamic' domains of the Irish Sea. The zooplankton community of the Irish Sea has also undergone significant change over the last thirty or so years. The most noticeable of these changes being a significant decrease in abundance of most of the species recorded. Some species distributions and abundances have been shown to be influenced by climate and it is highly likely that other species of plankton in the Irish Sea are also affected in this way. Climate, or more specifically the North Atlantic Oscillation (NAO), certainly has a major impact upon the physical-chemical environment of the region and this has a direct influence upon the ecology of planktonic organisms found in the Irish Sea.

This report is a contribution to the Department of Trade and Industry's (now Department of Energy and Climate Change) Strategic Environmental Assessment SEA2. It gives an overview of the phytoplankton and zooplankton community composition in the North Sea and how this has fluctuated through the latter half of the 20th Century in response to environmental change. The study is based on a unique long-term dataset of plankton abundance in the North Atlantic and the North Sea acquired by the Continuous Plankton Recorder (CPR). The dinoflagellate genus Ceratium dominates the phytoplankton community in the North Sea, but diatoms are also important, especially in the southern part. The normal annual blooms of plankton are discussed, as are harmful algal blooms (HABs), which appear to be on the increase, possibly due to a combination of climatic variability and eutrophication. Among the zooplankton, copepods are particularly important and constitute a major food resource for many commercial fish species, such as cod and herring. Calanus is the dominant copepod genus in the North Atlantic. Other important components of the plankton, meroplankton, picoplankton and megaplankton are also reviewed. Very small picoplankton (~1 micron in diameter) and much larger gelatinous members of the megaplankton (e.g. jellyfish and ctenophores) are poorly sampled by the CPR. Although the picoplankton represents a sizeable fraction of total primary production, its role in the marine ecosystem is poorly understood. The introduction of non-indigenous plankton in ship's ballast water has been in progress for about a century. There is growing concern about the risk of alien species, and the importance of protecting native biodiversity.