A comparison between 1928 and 2000 indicates major changes in the macrozoobenthos species composition and abundance on the SW coast of Finland (Baltic Sea)

Abstract

Segerstrle made detailed analyses of benthic communities in the Tvrminne region (SW coast of Finland). In addition to traditional presentation, he included illustrative photographs where the collected macroinvertebrates were laid on black background, in natural density, and reproduced in their natural size. This approach was replicated in the present study. The photographs highlight changes that have taken place during the past century in the benthic communities. In the deeper area there has been a change from an amphipod (Monoporeia affinis) dominated community to one dominated by the Baltic clam Macoma baltica. In the shallower study area the diverse Corophium volutator-M. baltica-chironomid community has been replaced by a community dominated by Macoma and a North American invader, the polychaete Marenzelleria viridis. Furthermore, the density of macroinvertebrates has declined considerably. The causes for these changes remain unclear, but are most likely connected to eutrophication related factors in the coastal ecosystem and concurrent interspecific interactions.