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' st ate in Neva Bay and the eastern Gulf of Finland showed spatial differences and temporal changes in the structure and functioning of the aquatic commun ities. Recent data revealed progressing eutrophication in the southern part of Neva Bay, viz. a pronounced increase of primary production and the prev alence of the production process over the decomposition of organic matter w hich had never been observed in Neva Bay before. At present, biomass of ben thos has dramatically decreased in the eastern part but increased in the so uth-western areas of the bay. Structure and spatial distribution of zooplan kton communities have changed both in Neva Bay and the eastern Gulf of Finl and. In the latter part of the estuary, blue-green algae became a dominatin g group of phytoplankton indicating serious alterations in the ecosystem ca used by anthropogenic stress.