摘要：During the last four decades the Baltic Sea phytoplankton went through a significant and gradual change in community composition. An analysis of several thousand quantitative samples from 1966 to 2008 reveals significant changes in the phytoplankton summer com- munity in most parts of the Baltic Sea. By using community gradient analysis methods (NMDS, DCA), we found a strong correspondence between sample ordination scores and sampling year (R 2 > 0.5). The association was stronger when the samples were geo- graphically more confined and the temporal range sufficiently large (R 2 > 0.8). Only in the southern Baltic Sea and the Kattegat had the salinity gradient stronger associations with the phytoplankton community composition as compared with the time effect over four decades. Eutrophication-related parameters (total and mineral nutrients) revealed low asso- ciation with the phytoplankton community composition in all Baltic Sea sub-basins (R 2 < 0.2). Also, known eutrophication gradients in the Baltic Sea had low association with phy- toplankton community. The phytoplankton community in the Baltic Sea is not in a steady state or equilibrium, and is not the same today as it was decades ago.
