抄録
Size-fractionated distribution of hot-water extractable phosphorus (EP) and particulate phosphorus and their temporal changes were studied in the South and North Basins of Lake Biwa over 20 days as a part of an international cooperative survey of Lake Biwa (BITEX'93). In association with typhoon-induced physical turbulence of the lake water, pronounced increases and decreases of EP levels of total particulate matter were observed. Distinct peaks on or after the days of the typhoon occured in both basins. Ratios of EP to Chl-a, EP to particulate carbon and EP to particulate nitrogen for the < 2 μm fraction also changed with marked peaks on or after the days of the typhoons, while the ratios for the > 20 μm fraction did not display a significant fluctuation. These results indicated not only a considerable supply of available phosphorus in the lake water by typhoon-induced physical turbulence but also a size-dependent, sensitive response of plankton to the short term change of phosphorus supply.