Bathymetric trends of the deep-sea meiobenthos distributed on the continental shelf, slope, and deep floor of the Ulleung Basin, East Sea

Understanding bathymetric patterns of deep-sea meiofauna is important for elucidating the influence of environmental variables on the characteristics of meiofaunal community structures. Depth-dependent meiobenthic community structures were investigated on the continental shelf, slope and deep basin of the Ulleung Basin in the southeastern East Sea. Meiobenthic samples were collected at 29 stations (water depth: 74–2155 m) from the continental shelf near the Korea Strait to the southern slope and basin areas of the Ulleung Basin during the summer cruise of R/V Eardo (June 2006). In total, 15 meiobenthic taxa (between two and nine taxa at each station) were identified. Nematodes formed the most abundant taxon (53–80%), followed by benthic foraminifera (7–39%). Meiobenthic abundance varied from 295 to 3697 ind. 10 cm−2 (nematodes, 106–3319 ind. 10 cm−2) at each station. The distribution of meiobenthic animals in the Ulleung Basin showed considerable spatial trends, with higher densities on the southern slope (1083 ± 249 ind. 10 cm−2) of the Ulleung Basin than the shelf (650 ± 220 ind. 10 cm−2) or deep basin (459 ± 214 ind. 10 cm−2) regions. Among the environmental parameters, TOC (total organic carbon) concentration was significantly correlated with meiobenthic abundance (r2=0.297), indicating that high food supply promotes meiobenthic abundance. Meiobenthic community structures showed depth-related trends from the continental shelf to the deep basin, with several meiobenthic taxa (e.g., amphipods, bivalves, harpacticoids, kinorhynchs, nauplius, nematodes, ostracods and polychaetes) contributing to these variations in the meiofauna.