Impact of environmental variables on the diversity and distribution of the megabenthos in the South Sea of Korea

Abstract

The South Sea of Korea is affected by three systems of currents: the high-temperature, high salinity Jeju Warm Current the low-salinity Yangtze River discharge flow from China and the cold-water bottom currents of the Yellow Sea. In addition, seasonal flow differences from various waterfalls drive environmental variability in these regions. As a result, the study area has high biodiversity, particularly the sea around Jeju Island, which is considered one of the world's most biodiverse areas however, information on the diversity of the megabenthos is very limited. Therefore, in this study, we analyzed the diversity and distribution of the megabenthos in the South Sea based on environmental factors. Megabenthos samples were collected using 10-min trawls towed at 18 stations from 2015 to 2016. The dominant species (>5% of the total density) were Anthopleura spp. (Actiniaria), Siphonalia spadicea fuscolineata (gastropod mollusks), and two subtropical species, Mactrinula dolabrata and Acila divaricate (bivalve mollusks). There were differences in biodiversity among the three sea regions (southwest, southeast, and northwest of Jeju Island) and the frontal zone of the South Sea. The total numbers of individuals and major taxa were generally higher in the frontal zone of the South Sea and northwest of Jeju Island. Biomass was particularly high in the frontal zone of the South Sea. Environmental factor analysis showed that differences in biodiversity were related to sediment (grain size), salinity, and temperature. These results indicate that changes in marine environmental conditions in the South Sea of Korea affect megabenthos species composition and diversity.