영산강 하구역 및 목포 연안 해역 식물플랑크톤 1차생산력의 시∙공간적 변화

Abstract

Temporal and spatial variations of primary productivity were investigated in the estuary of Youngsan River and Mokpo coastal areas in 2009. After heavy rain, concentrations of ammonium, phosphate, and silicate increased at six stations in August. The torrential rainfall may cause an increase in untrient concentrations during summer. There is no limitation of nutrients(except for February at the mid-Youngsan estuarine region YS2)but a potential phosphate limitation was apparent at all stations. Silicate depletion was observed at YS2 in February due to a massive diatom bloom. The trophic status of the Youngsan estuary and Mokpo coastal areas were inferred from an assessment of the primary productivity. In February and May, YS1(upper Youngsan estuary site) and YS2, YS3(near the Youngsan river estuary barrage), MP1 (upper Mokpo coastal region site) were appropriately assigned to the mesotrophic category. MP2(mid-Mokpo coastal region site) and MP3(outer site of Mokpo coastal region) were assigned to the oligotrophic category. All stations were classified to the oligotrophic status in November. In August, after heavy rain, Youngsan estuary stations maintained mesotrophic status. On the ofter hand, Mp1 and MP2 were classified in the eutrophic category and MP3 to mesotrophic status. In Particular, primary productivities of MP1 and MP2 were 9 and 7 times higher respectively than the standard of eutrophic status(1,000-mgC m-2 d-1). These results suggest that a massive freshwater discharge from the Youngsan River estuary should be considered a Main factor in the occurrence of phytoplankton bloom in Mokpo coastal areas during summer. Seasonal variations of primary productivity are closely related with depth-integrated Chl.a.