Relationship between dissolved oxygen concentration of bottom water and macrophyte biomass in the southern basin of Lake Biwa, Japan

The horizontal distribution of dissolved oxygen (DO) concentrations on the lake bottom was investigated on September 2-5, 2002. At 36 out of the 84 sites, DO concentrations were at less than 50% of saturation. The biomass of macrophytes was investigated on September 6- 11 at 44 sites, and ignition loss of sediments was investigated at 41 sites on September 17-18. The results of multiple regression analysis suggested that DO concentrations could be estimated using the biomass of Egeria densa, Myriophyllum spicatum, and Potamogeton maackianus, and the water depth as explanatory variables (R = 0.65, R' = O.61, n = 44, P 0.01). Both the partial correlation coefficient and partial regression coefficient indicated that biomass of Egeria densa was the most influential environmental factor on the fluctuation of DO concentrations on the bottom water.