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Biologische Zustandseinschätzung der Ostsee im Jahre 2011

Abstract The time series on species composition and biomass or abundance of phyto- and zooplankton as well as macrozoobenthos in Kiel Bight, Mecklenburg Bight and the Arkona Sea, existing since 1979, was continued in 2011. The phytoplankton spring bloom developed later than usual after the cold winter; it reached its peak at the end of march/beginning of April 2011 in the western Baltic. At least in the Arkona Sea, it was a classical diatom bloom, but formed by the unusual species Achnanthes taeniata. In Kiel Bight, we found abundant dinoflagellates (Peridiniella danica) and Dictyochophyceae (Verrucophora farcimen). Also these species are rather new and unusual in this area. In the central Baltic, Mesodinium rubrum formed a bloom in May. The cyanobacteria developed already in the first half of July and reached the maximum extent on 12 July 2011. A typical summer diatom bloom could not be found during the cruise in August 2011. In autumn 2011, dinoflagellates were dominating in the w...