Effects of eutrophication and invasion of Dreissena polymorpha in the coastal zone of the eastern Gulf of Finland

Abstract

. Ecosystem studies in the littoral zone of the Neva estuary have shown that eutrophication is a serious environmental problem for the coastal zone of the eastern part of the Gulf of Finland. It brings about an intensive development of filamentous algae Cladophora glomerata and periodical blue-green blooms. Wave action detaches Cladophora mats from substrates and causes an intensive secondary pollution of the beaches in the St. Petersburg Resort District. The zoobenthos community is dominated by caddis fly larvae in the shallow littoral. The alien species Dreissena polymorpha in deeper littoral is facilitating filamentous algae growth, clearing the water and recycling nutrients. An important recovery measure in the ecosystem management in the coastal zone is removal of hard substrates from shallow waters to curb the development of filamentous algae. Another important measure is nutrients reduction and control of the P : N ratio in the coastal zone of the Gulf of Finland.