Macrobenthos were collected in each season by SCUBA diving to investigate the benthic faunal assemblages in the coastal water of Chagwido from September 2004 to August 2005. A total of 201 macrobenthos identified, 74 species (37.2%) of Mollusca were found; 43 species of Arthropoda (19.2%); 34 species of Cnidaria (16.7%) and others including 18 species of Porifera (9.8%). Mean density and biomass were estimated to be 455 individual/m2 and 15,565.0 g/m2, respectively. Whereas annelids was predominant in biomass (1,558.8 g), gastropods were the most dominant faunal group in terms of abundance (5,391 individuals) and the number of species. The dominant species were Trochus sacellus, Batillus cornutus, Pagurus gracilipes, and Cantharus cecillei. The seasonal variation of the number of species and individual Mollusca and Arthropoda was observed. There was a slow increase in spring, the peak in summer, and a slow decrease in autumn and winter. The dominance index was the highest in Gosan and lowest in Yongdang. The biodiversity indice (H') were 1.760-3.497 in each station. Mean biodiversity index was 2.858 (H'). The diversity index, the eveness index (E'), and the dominance index (R) were 3.218-3.743, 0.648-0.720, 17.690-22.826, respectively, in each station.
