Ecological Systems and Devices Annotation << Back Study of the phytoplankton block of the Baltic Sea ecosystem in summer 2010 Domanov M.M. Zernova V.V. Pautova L.A. Melnikova Z.G. The data about phytoplankton community in the Baltic cross-section Kaliningrad–Sankt-Petersburg are analyzed. The data about phyto- and pico-plankton quantity, biomass and composition in pelagic part of the Baltic Sea, Gdansk Bay and Finland Bays were obtained in summer 2010 during the beginning of phytoplankton summer vegetation. The average number of cells in small fraction is 50 times higher than in large fraction, and average biomass of small fraction is 20 % of biomass of a large one. The maximum common biomass (13 080 mg/m3) was on the coastal station in Gdansk Bay The maximum biomass of the large fraction (10 083 mg/m3) was generated in the Fin Bay due to vegetation of diatomic algae Thalassionema nitzschioides. The Baltic phytocene characteristic features are typical for the summer period and correspond to average long-term observations. Comparing the average values of Baltic pelagic phytoplankton quantity and biomass with the previous data points out a small increase of quantity and a healthy increase (5 times) of biomass during the last 10 years. Toxic phytoplankton is represented by species typical for the Baltic Sea, quantity and biomass of this phytoplankton being insignificant. Keywords: ecology; eutrophication; phytoplankton; biomass; species; structure; trend; Baltic Sea. Contacts: E-mail: domanov@ocean.ru Pp. 42-48.