On the spatial and temporal variations of zooplankton in Northeast Atlantic shelf waters

Résumé

In the present study we have used zooplankton time-series, for the 1999 ¿ 2013 period, coming from long-term monitoring programs carried out at four sites placed along a latitudinal gradient within the Northeast Atlantic Shelves Province, the Bay of Biscay (two sites with a different trophic status), the English Channel and the Scottish North Sea, to analyze the effect of latitude and trophic status in zooplankton dynamics and community structure. Results allowed to infer that (1) the magnitude of interannual, seasonal and residual components of zooplankton variability differed between sites mainly in relation to local determining factors, (2) the seasonal patterns and taxa abundance of zooplankton differed between sites in response to latitude and trophic status-linked environmental variations, (3) between-site differences in zooplankton seasonality were mainly driven by the seasonal cycle of phytoplankton biomass, with an annual maxima delay alongside latitude and trophic status, (4) the percentage of zooplankton seasonal variability explained by environmental variables increased with latitude and trophic status, as did the interannual coherence of environmental variables seasonal patterns, (5) the main phenological changes of zooplankton taxa throughout the study period showed opposite trends at the northernmost site (seasonal advance) and the southernmost sites (seasonal delay), that were mainly related to different climatic indices, (6) the interannual variations of zooplankton community showed gradual changes (trends) at every site, with the interaction between water temperature and month being selected as the main driver of change almost at every site, (8) none representative taxa showed the same trend at all sites, but Acartia presented an increase in the southernmost sites and a decrease at the northernmost site, likely due to the seasonal differences with latitude constrained by thermal preferences, and (9) between-site differences in zooplankton community structure at the coarse groups level was mainly linked to latitude and temperature, but at copepod and cladoceran genera level, to local features.