陸奥湾における夏季のマクロベントスの密度と群集型の経年変動

抄録

Annual changes in density and community types of the macroinvertebrates inhabiting the extensive mud and sandy mud bottoms in Mutsu Bay, Aomori Prefecture were studied on the basis of summer samples obtained during 1979-1988 (except for 1984). Although two samplers, Tamura grab and Smith - McIntyre grab, were used at the mud and sandy mud stations, their relative efficiencies were similar in terms of the numbers of collected individuals, the species richness, and species composition. Mud and sandy mud bottoms in the bay were consistently dominated by polychaetes, accounting for 71∼93% of the total number of individuals. Remarkable annual fluctuations in abundance were observed for several main polychaetes. However, the total abundance of macrofauna in the bay was relatively stable, because species with high density occurred successively. From year to year, the types of macrofaunal community changed dramatically with variations in abundance and spatial distribution of the main polychaetes. In general, when habitats of dominant species overlapped, the density of one of these species reduced markedly in the following year. These facts suggest the possibility that the competitive interaction between the same trophic organisms affects the abundance of the main polychaetes and the community structure within this study area.