LAUSR

Deterioration of the sediment environment and benthic ecosystem is an undesirable effect of eutrophication, but little is known about the response of macrobenthic communities to eutrophication and their long-term recovery. In the present study, temporal changes in benthic ecological status, associated with reductions in anthropogenic impacts on a largest semi-enclosed sea in Japan, were determined using long-term monitoring data from water and sediment quality based on the multivariate AZTI Marine Biotic Index (M-AMBI), focusing on spatial differences in anthropogenic impacts. Several sub-areas were classified based on Chlorophyll a (Chl.a) concentrations in surface water during the 1980s. Chl.a concentrations decreased in all sub-areas except the sub-area with <2 μg Chl.a L-1 from the 1990s-2010s. On the other hand, total organic carbon contents in sediment decreased and M-AMBI values increased in all sub-areas during this period may be due to reduced lateral organic matter advection from surrounding areas.