| Summary: | Spatial variability of the effect of sea surface temperature (SST) change on the phenology of eight representative plankton taxa of the eastern North Atlantic was investigated. The results confirm that the strength of correlation between seasonal peak in abundance (7) and SST varies between taxa, and also varies geographically, with a general distinction between shallow and coastal areas (including the North Sea) and oceanic areas. Wind mixing is known to have an effect on stratification of the water column, and it is thought that increased wind mixing may be leading to a breakdown in the link between T and SST, contributing to some of the spatial variability in plankton response, as both temperature and wind speed are positively correlated with the North Atlantic Oscillation (NAO). Some of the inter-species variation in phenology is thought to be related to non-uniform amplification of the effect of SST thanks to the non-linearity of feeding relationships in the complex pelagic ecosystem. Other phenology changes appear to be due to reduced production, as higher temperatures reduce productivity of cold-affinity species such as Calanus fmmarchicus, reducing abundance towards the end of the seasonal cycle in particular. Further study of spatial variability is recommended, with multivariate analysis taking into account additional environmental variables and also biological indices such as species abundance and diversity to help elucidate some of the pattems seen here. KEY WORDS: Plankton, spatial variability, phenology. North Atlantic, climate change. Faculty of Science, The Sir Alister Hardy Foundation for Ocean Science, Plymouth, UK
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