Species composition and distribution of macrobenthos in the intertidal zone of Kunashir Island (South Kurile Islands), Russia

Abstract

Characteristics of vertical distribution, species composition and biogeographical structure of macrobenthos of the intertidal communities of Kunashir Island (South Kurile Islands) are described. In the rocky and bouldery intertidal zones, communities dominated by barnacle Chthamalus dalli and a gastropod species Littorina sitkana with the poor species composition of the macrobenthos are typical for the upper intertidal subzone. The middle intertidal subzone is occupied by fucoid assemblages. The dense beds of laminarian algae dominate in the lower intertidal subzone with the total macrobenthic biomass up to 100 kg wet wt m?2. On wave-exposed sandy beaches formed by clean sand, populations of the macrobenthic organisms are very poor, and macrophytes and the other attached forms are absent. The communities dominated by eelgrass Zostera japonica and a gastropod species Batillaria cumingii are found only in the sandy intertidal zones of the southern coast of Kunashir Island, in Izmeny Bay. Reduction of species richness and increase of biomass of macrobenthos have been recorded from 1963 to 1991 in Izmeny Bay, and it is due to the fact that this area has been exposed to anthropogenic impact. At least, 563 species of macrobenthos are found in the intertidal zone of Kunashir Island. Pacific low-boreal and Pacific wide-boreal species are dominant. Warm-water species are more abundant in the intertidal zones of Izmeny Bay and on the Sea of Okhotsk coast as compared to those on the Pacific coast of Kunashir Island. It is probably associated with the flow patterns of the Soya Warm Current. Species composition and distribution of the intertidal macrobenthos of Kunashir Island are typical for the low-boreal intertidal zone with irregular diurnal and semi-diurnal tides. The intertidal zones of Kunashir Island and neighboring Shikotan Island have similar species composition and distribution patterns of the macrobenthic communities.