Akanoi Bay, Lake Biwa seasonal changes in porewater phosphorus

Lake Biwa is the largest lake in Japan (674 km') (Fig. 1). Unfortunately, nutrient loading from urban growth and changes in agricultural practices have resulted in eutrophication (NAKAMURA 1995). Some sub-basins such as Akanoi Bay are considered hypertrophic (HIRAYAMA et al. 1993). The eutrophic southern basin is the major drinking water supply for about 15 million people, including Osaka (ÜKUDA & KUMAGAI 1995) and there are concerns about the production of algal toxins such as microcystin (PARK et al. 1993). KURATA (1994) found that the highest rate of phosphorus release from sediments in Lake Biwa was in Akanoi Bay (mean of 2.8 mg/m'/day).