Abstract
The field survey conducted at Lake Biwa showed that the vegetation area of submerged macrophytes increased by 15% in North Lake in 2002, 73% in South Lake and 36% overall in comparison with that of 1997. During the growth period of the submerged macrophytes in 2002, the water level of Lake Biwa was 50 cm lower than in 1997, and the vertical distribution of vegetation area of submerged macropytes also shifted 50 cm deeper. In South Lake, in addition to the shift of vegetation area, the area size at the same water level significantly expanded. Increased light availability due to decreased water level expanded the vegetation area of the submerged macrophytes during the growth period. There are signs of positive feedback that the clarity of water transparency becomes better as the number of submerged macrophytes increases.
