An investigation was carried out on benthic macrofauna from the sandy areas of the coastal water of Futaba, Fukushima Prefecture, Japan, to clarify the pattern of faunal distribu-tion and environmental factors affecting their occurrence.
A total of 148 species were collected using a Smith-McIntyre grab. Among them, 51 species of annelids (74.4% in individuals), 60 species of arthropods (17.4% in individuals), and 20 species of molluscs (5.9% in individuals) took up almost the entire collection.
The numbers of individuals and species, species diversity, species evenness and sediment particle diversity were closely related to the depth of the sampling site. Based on cluster analysis via the species similarity index (Cπ), the study area was divided into three zones plus one isolated point which was situated in a neighboring port. These results clearly indicated the divisions of animal distribution in accordance with the depth of water.
The macrofaunal habitat segregation according to depth, differences in behavioral character (ability for sand-burrowing, feeding habits) of gammarus and bivalves, and the results of analyses of bottom sediments suggest that the principal factors in separating animal distribution seem to be the mechanical effects of waves and the difference in the quality of sediments between nearshore and offshore points.