PROPORTION OF COPEPOD BIOMASS DECLINES WITH DECREASING SALINITY IN THE BALTIC SEA

The biomass ratio of copepoda/cladocera decreased in the Northern Balt ic Archipelago Sea (SW Finland) in concert with a decrease in the seaw ater salinity during the 1980s. There also was an increase in freshwat er run-off from the watershed of the Baltic Proper. Seawater salinity correlated negatively with freshwater run-off with a time lag of sever al years. The abundance percentages of most dominant zooplankton speci es correlated significantly with salinity, either positively (large ne ritic copepods), or negatively (freshwater cladocerans). All data sets together indicate a close connection between the functioning of the p elagic Baltic Sea ecosystem and large-scale weather patterns over the run-off area. (C) 1998 International Council for the Exploration of th e Sea.