Spatio-temporal variation in zooplankton community structure in the western subarctic North Pacific based on the historically collected... » More

Spatio-temporal variation in zooplankton community structure in the western subarctic North Pacific based on the historically collected zooplankton samples for 1960s - 2000, the Odate Collection, was investigated in relation to decadal climatic and hydrographic variations. Species and size structure of copepods in the region varied well responding the decadal dynamics of the subarctic and subtropical oceanic currents, Oyashio and Kuroshio, respectively. Spinning up of both of the currents after the North Pacific climatic regime shift in the mid-late 1970s induced northward shift of smaller subtropical species and southward shift of larger subarctic species, resulting in increase of species diversity (H’) in the southern Oyashio area and transition regions of both currents. As lifecycle strategies and ecological roles are distinctive between subarctic and subtropical copepod species, the observed biogeographical shift of copepod community was considered to increase zooplankton functional diversity in this region. Possible consequences of the change in the functional diversity in terms of the link with higher trophic levels and biogeochemical cycle will be discussed in the presentation. 

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