Response of aquatic communities to anthropogenic stress: a comparative study of Neva Bay and the eastern Gulf of Finland

A comparative study of the long-term data (1982-1996) on the ecosystems' state in Neva Bay and the eastern Gulf of Finland showed spatial differences and temporal changes in the structure and functioning of the aquatic communities. Recent data revealed progressing eutrophication in the southern part of Neva Bay, viz. a pronounced increase of primary production and the prevalence of the production process over the decomposition of organic matter which had never been observed in Neva Bay before. At present, biomass of benthos has dramatically decreased in the eastern part but increased in the south-western areas of the bay. Structure and spatial distribution of zooplankton communities have changed both in Neva Bay and the eastern Gulf of Finland. In the latter part of the estuary, blue-green algae became a dominating group of phytoplankton indicating serious alterations in the ecosystem caused by anthropogenic stress.