Measurement and verification of rates of sediment phosphorus release for a hypereutrophic urban lake

The contribution of sediment release to the phosphorus budget of hypereutrophic Onondaga Lake was determined through laboratory measurements made on intact cores. Rates ranged from 9–21 mg P m^–2 d^–1 with a mean of 13 mg P m^–2 d^–1, values similar to those observed in other lakes of comparable trophic state. There was no statistically significant trend in rates in time (July versus September) or in space (location along the major N/S axis of the lake). Rates of sediment phosphorus release measured in the laboratory compared favorably with the observed rate of soluble reactive phosphorus accumulation in the lake's hypolimnion. The sediments are the second largest source of phosphorus for Onondaga Lake, contributing 24% of the overall phosphorus load to the system.