Abstract
To evaluate the loads of nitrogen, phosphorus and COD constituents from the bottom sediment in Lake Sanaru, one of the most eutrophic lakes in Japan, their release fluxes from the sediment were measured in a laboratory experiment using sediment cores. The cores were collected from two sites in August 2005. The release flux of nitrogen was underestimated due to the volatilization of ammonia in water during the experiment. The estimated release fluxes of phosphorus and COD constituents of the entire lake corresponded to approximately 6- and 0.6-fold their respective inflow fluxes. In addition, the nutrients are transferred from the sediment in dissolved forms that phytoplankton can use. Owing to the shallowness of the lake (mean depth:∼2 m), the nutrients are used by phytoplankton immediately after their release from the sediment. These suggest that nutrient release from sediment has a large contribution to primary production in Lake Sanaru. This nutrients release is probably due to the rapid decomposition of large amounts of dead phytoplankton deposited at the lake's bottom.
