Species composition and community structure of the soft-bottom macrobenthos at the coastal and its adjacent areas of Dokdo, the East Sea of Korea

Abstract

This study investigated the species composition and community structure of the soft-bottom macrobenthos around coastal and its adjacent areas of Dokdo. Animals were collected using a Smith-McIntyre grab (0.1m2) at 13 sites in May and August 2017. The mean depth of the shallow sites was 56m and the mean depth of its adjacent sites was 1,490m. There was no variation of the bottom salinity between at the shallow and deep areas. The bottom temperature increased from spring to summer season, but the bottom dissolved oxygen decreased. A total of 158 species/4.1m2 were collected from 111 species/2.1m2 in May to 107 species/2.0m2 in August. These number of species was higher than that of the coastal of East Sea. The mean density of the macrobenthos was 542 individuals/m2 from 267 individuals/m2 at deeper area to 1,120 individuals/m2 at shallow area. The dominant species (>2% of the total density) were Melita denticulata (amphipod), three mollusks Tucetonella munda, Limatula japonica, and Pleuromeris pygmaea, and three polychaetes Syllis amica, Amphinome sp1., and Terebellides horikoshii. The most of dominant species appeared at the coastal area of Dokdo, but polychaete T. horikoshii appeared only at deeper area of Dokdo. The community structure of the macrobenthos divided into four groups by the environmental conditions. These result indicate that variations in marine environmental conditions from shallow to deep area of Dokdo influence the species composition and community structure of macrobenthos.