Zonation of macrofaunal assemblages on microtidal sandy beaches along the Japan Sea coast of Honshu

Abstract

Zonation has been a major focus of intertidal ecology. In general, sandy beaches are thought to have three zones (supralittoral, littoral, and sublittoral zones). In the present study, 41 areas of sandy beaches were surveyed along the Japan Sea coast of Honshu (from Aomori to Yamaguchi Prefectures) characterized by a small tidal range, large seasonal fluctuations in the mean tide level, and harsh wind-driven waves in winter, and the applicability of the three-zone scheme was examined. Overall, a total of 316 beach stations were surveyed, 28 taxonomic units were identified, and the most abundant species was the amphipod Haustorioides japonicus. The taxonomic units were grouped using multivariate techniques into a total of 7 assemblages, and the relationship of these assemblages to zonation was examined. Investigation of the indicator species of the 7 assemblages and their vertical position on the beaches showed that one assemblage corresponded to the supralittoral zone (indicators were talitrid amphipods and the isopod Tylos granuliferus). Another assemblage corresponded to the sublittoral zone, and the other five assemblages to the littoral zone. The assemblage of the sublittoral zone tended to disappear on the northern beaches, while one of the littoral assemblages whose indicators included a mysid species, Archaeomysis kokuboi, tended to occur on the northern beaches. Thus, the three-zone scheme can be applied to sandy beaches of the Japan Sea, but there are large variations among the beaches.