한국 항만에서 환경요인이 식물플랑크톤 군집 변동에 미치는 영향

Abstract

To understand the environmental factors affecting dynamics of phytoplankton communities at the busiest ports (Pusan, Ulsan, Incheon and Gwangyang) of Korea, we seasonally investigated the physico-chemical factors and phytoplankton assemblages from February 2007 to November 2008. Diatoms were the majority in the phytoplankton communities (78%). Maximum abundance of diatoms was observed at Pusan in summer 2007, and at Ulsan in spring 2007. During each period, over 60% diatoms at Pusan were Chaetoceros debilis and Ch. pseudocrinitus, and Detonula pumilia dominated at Ulsan. At the Incheon and Gwangyang ports characterized as eutrophic and semi-enclosed environments, the abundance of diatoms peaked in winter when Skeletonema costatum dominated. It corresponded to condition of lower salinity, higher concentration of chemical oxygen demand and total suspended solids compared to Pusan and Ulsan. When diatoms bloomed at the ports investigated, there were very low concentration of silicate and nitrate (p<0.001), indicating strong nutrient uptake by the dominating diatoms. Dinoflagellates, the next most abundant group, occurred frequently at the Pusan, Ulsan and Gwangyang ports in summers, when their abundance was significantly correlated with increasing temperature and decreasing salinity (p<0.05). Also, the concentration of phosphate was high (>1 μM) at the four ports in summers. In contrast, low abundances of dinoflagellates occurred during the study period at Incheon. At all ports, the predominant diatoms characterized waters with low concentrations of nutrients such as silicate and nitrate, while dinoflagellates mainly occurred in summers, with increasing temperature, low salinity and high phosphate concentration.