이른 봄 거문도 도내해의 해양환경과 식물플랑크톤 군집 분포특성

An environmental characteristics on the water type and the distribution of phytoplankton community in Donaehae of Geomundo, South Sea of Korea during early spring 2005

We carried out a study on the marine environment, such as water temperature, salinity, density and chlorophyll a, and the distribution of phytoplankton community, such as species composition, dominant species and standing crops in the Donaehae of Geomundo, South Sea of Korea during early spring 2005. According to the analysis of a T-S diagram, two characteristics of water type were identified. The first was characterized by high temperature and low salinity in the surface layer influenced by freshwater run offs from Dongdo of Geomundo and the second by low temperature and high salinity in the surface to bottom layer appeared from the mixing waters in Donaehae of Geomundo. The thermocline was not formed at the intermediate depth. Chlorophyll a concentration was low values with it’s ranging from 0.75 ㎎/㎥ to 1.32 ㎎/㎥ in surface layer. The phytoplankton community in the surface was composed of a total of 35 species belonging to 26 genera. Dominant species were 2 centric diatoms, Skeletonema costatum, Chaetoceros debilis and 2 pennate diatoms, Thalassionema nitzschioides, Cylindrotheca closterium. Standing crops of phytoplankton in the surface layer were very low with cell density ranging from 0.8 to 12.0 × 103 cells/L. In the early spring, the phytoplankton community in Donaehae of Geomundo was showed very simple patterns in species composition, dominant species and the distribution of standing crops.