Abstract
Using megabenthos samples collected in Ise Bay, central Japan, from 1993 to 2002, seasonal and interannual variations in megabenthos communities were analyzed as related to environmental characteristics in the bay bottom waters, particularly to the oxygen-poor water. Megabenthos communities were separated into two groups（A and B）: Group A was located mainly in the central areas to the innermost ones with silt-clay sediments, while Group B was located mainly in the eastern areas to the bay mouth ones with sandy sediments. Damage due to the oxygen-poor water was marked for Group A, although both groups showed the highest/maximal density, biomass, and species richness of the megabenthos in spring to early summer just before the development of the oxygen-poor water, and the lowest/minimal ones in the fall just following the existence of this water. Then, the density, biomass, and species richness of the megabenthos increased mainly through new recruitment（i. e., smaller individuals）in winter.
