Mesozooplankton community indicates climate changes in a shelf area of the inner Bay of Biscay throughout 1988 to 1990

Abstract

The mesozooplankton community was monitored at both coastal and offshore sites of the Basque shelf (inner Bay of Biscay) during 1988–1990 This was considered of interest because the local climate change toward dry conditions was found to be responsible for changes in shelf-water properties. In addition to seasonal changes, interannual variations in mesozooplankton abundance and composition were evident, and primarily related to the year-to-year increase in water temperature and salinity. The increasing trends in copepod dominance, coupled with the increasing abundance of species with oceanic affinity (e.g. Euchaeta hebes), were presumably a response to the increase in oceanic features in the shelf area. In the same way, the substantial year-to-year increase in the abun dance of species with summer-autumn development was attributed to the progressive warming. Among these species, the case of Temora stylifera is discussed specifically because this species was very scarce in 1988, but showed unusual high abundances for the study area, and dominated the summer-autumn assemblage in 1990. We think that T.stylifera can be a key species in monitoring climate-oceanological changes affecting the Bay of Biscay. Results are also discussed in the context of the long climate-oceanological series for the Bay of Biscay, and its biogeographical status.