TEMPORAL AND SPATIAL VARIABILITY OF ZOOBENTHIC COMMUNITIES IN ARCHIPELAGO WATERS OF THE NORTHERN BALTIC SEA - CONSEQUENCES OF EUTROPHICATION

A large-scale spatial (52 sampling stations in two areas; one previously affected by numerous sources of enrichment, and one pristine area used as a standard reference for coastal monitoring) and temporal (1972-1989) analysis of hydrography and benthic macrofauna in the archipelago waters of Aland, northern Baltic Sea, revealed significant changes of the ecosystem. The nutrient levels exceeded the criteria for eutrophicated waters at all stations, and the benthic macrofauna showed significant alterations in all parameters analyzed. In the area previously (1972-73) disturbed, reduced complexity in terms of diversity and evenness (i.e. functional responses) were recorded, whereas the changes in the previously undisturbed area are classified as structural. The main conclusions are that (a) no truly "natural" coastal reference areas can be found in the northern Baltic, and (b) the importance of the local effluents will add to the large-scale effects of eutrophication.