The Gulf of Finland

摘要: In this chapter, we describe the unique physical and biogeochemical conditions of Gulf Finland. Although morphologically a direct continuation Baltic Proper, several features distinguish markedly from other parts Sea. Relative to its surface area, Finland has largest catchment area highest freshwater inflow within The external loading nitrogen (N) phosphorus (P) relative are about two three times, respectively, those distinct but unstable salinity stratification, which makes sea very sensitive perturbations. At may lead e.g. deep water anoxia/hypoxia, elevated benthic release P extensive cyanobacterial blooms. poor oxygen in caused primarily by voluminous spring bloom preceding sedimentation detrital plankton material, turn is high wintertime nutrient concentrations. Poor intensified sediment have led strongly increasing deep-water winter concentrations inorganic over last 10 years. contrast, N decreased since late 1980s, suggesting effect at same time. This latter phenomenon probably contributed magnitude phytoplankton blooms 1990s. prevailing weakened populations invertebrates further retention removal capacity sediments. most important controlling factor recent adverse changes fish stocks been hydrographical changes. Especially coastal waters, eutrophication associated consequences shifted biomass dominance percids towards cyprinids. Summertime going on least 1970s. Since mid-1990s main reason for development, both open seems general development internal loading, rather than any land-based loads. reduction load is, however, only permanent way counteract accumulation labile organic matter nutrients, as well summertime