Zooplankton community during the transition from spring bloom to oligotrophy in the open NW Mediterranean and effects of wind events. 1. Abundance and specific composition

Short-term changes in the zooplankton community were investigated at a time -series station in the open NW Mediterranean during the DYNAPROC cruise pro gramme (May 1995). Based on the samples obtained with three devices (12 l b ottle, 200 mum and 500 mum mesh nets), the abundance and specific compositi on are presented for mesozooplankton (copepods mainly), macroplankton and m icronekton. Over the 3 week sampling period, overall density of the copepod community decreased and changes in the specific composition occurred. The decline was also observed in nauplii and was more marked in small-sized cop epod species than in larger ones; one species, Centropages typicus, even di sappeared. An increase in the proportion of carnivorous organisms appeared in both copepods (Euchaeta acuta, Heterorhabdus spp.) and euphausiids (Nema toscelis megalops, Stylocheiron longicorne). These changes are discussed in relation to environmental features and in the context of seasonal variabil ity, the observational period coinciding with the transition from spring bl oom to oligotrophy in this area. Effects of a major wind event that appeare d to have induced long-lasting changes are also explored.