Aquatic biodiversity under anthropogenic stress: an insight from the Archipelago Sea (SW Finland)

The Archipelago Sea in the northern Baltic has been subjected to large-scal e cultural, economic and ecological changes, especially during the last thr ee decades. Environmental threats originate from both basin-wide sources, a ffecting the whole Baltic Sea, and from local sources, such as nutrient loa ding from nearby river outflows, intense agriculture, fish farming, ships' traffic, boating, and man's physical impacts on the landscape and seascape. Both the Aland archipelago and the Archipelago Sea have been listed as hot -spots by HELCOM, Baltic Marine Environment Protection Commission, eutrophi cation being the main threat to the aquatic environment. In this study we r eview how biological communities have reacted to an increase in man-induced multisource stresses. Changes in plankton, benthic animals, macroalgal ass emblages and fish communities have been documented in most parts of the Bal tic Sea since the 1970s. What remains to be understood is the importance of these structural changes for the functioning of the Archipelago Sea ecosys tem under various levels of human impact.