A preliminary study of the effect of pelagic organisms on the macrobenthic community in the adjacent East China and Korea Strait

Abstract

Despite the impacts of the climate changes on the pelagic ecosystem, few studies have examined the pelagic-benthic coupling in the adjacent East China Sea and Korea Strait. Therefore, the species composition and abundance of the macrobenthic community, as well as the potential food sources of benthic fauna were investigated in the present study using stable isotope analysis (δ13C and δ 15N) for suspended particulate organic matter (SPOM), sedimentary organic matter (SOM), phytoplankton, and zooplankton. A total of 157 macrobenthic fauna were collected, and the density of the macrobenthic fauna ranged from 4 to 434 ind./0.25 m2, with an average density of 149 ind./0.25 m2. The density of tile benthic fauna increased moving from offshore shelf sites to coastal sites adjacent to the Korea Strait. Cluster analysis showed that the macrobenthic communities consisted of three distinct groups: group A in the Korea Strait, group B in the East China Sea, and group C near Ieodo. The dominant species in group A were the ampbipods Photis japonica and Ampelisca miharaensis, followed by the polychaete Scolotoma longifolia. Environmental variables, such as the temperature of the seawater and sediment, and oxygen, and chlorophyll a levels, appeared to affect the structure of the community, suggesting the importance of coupling with the pelagic system. The δ13C values of SPOM and zooplankton ranged from -22.97 to -23.5‰ and -19.92 to -21.86‰, respectively, showing a relatively narrow range (<1‰) between the two components. The difference between the (δ13C values of SOM and pelagic organic matter was also within 1‰, suggesting that the SOM originated from the pelagic system, which is an important factor controlling the macrobenthic community.