Ecological study on the toxic Microcystis in the lower Nakdong river = 낙동강 하류 수계의 독성 Microcystis 생태 연구

Abstract

The standing crop of genus Microcystis, microcystin concentrations and environmental factors were monitored at stations of the lower reaches of the Nakdong River in 1998 and 1999 during the periods of its occurrence. The Microcystis were observed from may to October, and the cell density was highest at Station Seonam up to 250,000 cellsml-1 forming scum over the water surface. There were significant relationships between the standing crop of Microcystis and nitrate nitrogen, total phosphorus concentrations and pH. Presumably these parameters were important in the succession to Microcystis dominated phytoplankton community in the summer period in the river. However, ammonium nitrogen, phosphate phosphorus concentrations and N/P ratio were not critical factors. The Microcystis bloom was notable above 25℃ of surface water temperature. Microcystins were detected from May to November in the algal materials from the river. The 84.2% of algal materials with Microcystis exhibited the microcystin with the maximum of 1711.8㎍g-1 dw. The microcystin concentrations in the algal materials were significantly related to the standing crop of Microcystis, which was the primary determinant factor in the toxin level of algal materials. The concentrations were also significantly related to pH of the water column in the positive pattern.