Seasonal development of mesozooplankton abundance, biomass and production were studied on the SW coast of Finland in three hydrographically distinct areas with different phytoplankton dynamics. In addition, the present species composition was compared to that at the beginning of the century, using a multidimensional scaling analysis. Mesozooplankton biomass and production were dominated by only a few species: the largest part of the production in the archipelago and open sea areas (11.3 g C m-2 year-1 and 28.1 g C m-2 year-1, respectively) consisted of that by raptorial and suspension-feeding calanoid copepods (Acartia bifilosa and Eurytemora affinis) and of that by rotifers (Synchaeta baltica), while annual mesozooplankton production in the bay area (10.5 g C m-2 year-1) was mainly due to production of filter-feeding cladocerans (Daphnia cucullata and Bosmina longispina) and predatory cyclopoid copepods (Thermocyclops oithonoides). The food chain in the bay area seemed to be based on heterotrophic organisms; the dominant rotifers and cladocerans were feeding on bacteria and were in turn eaten by cyclopoid copepods. Salinity and trophic status of the area seemed to be the main factors determining species composition, while seasonal development of biomass and production were mostly affected by temperature and, probably, predation. The slight change in species composition in the study area since the beginning of the century may be due to increased salinity.
|Publication status||Published - 1999|