Assessing ecological status of an urban estuary in the northern Baltic Sea and its recovery from pollution

摘要

Eutrophication is a worldwide threat to surface waters. National and international initiatives have been implemented during recent decades to protect and improve the quality of water resources. Recovery of surface waters from pollution has usually been slow but some studies have demonstrated rapid recovery in lakes (e.g. Schiendler 1974, Bradshaw & Anderson 2001) and in coastal waters (e.g. Lappalainen & Pesonen 2000). Assessing surface water status and stage of recovery requires establishing reference conditions, a baseline against which the changes can be measured. Depending on physical features, these conditions are highly variable across both inland and marine waters. Characterization of reference conditions has recently received increased attention as part ecological classification in the European Union Water Framework Directive (WFD, ANON. 2000). The overall objective of the WFD is to maintain and improve the ecological quality of all waters and, ultimately, to achieve good environmental quality by controlling pollution sources.