A comparison of internal phosphorus loads in lakes with anoxic hypolimnia: Laboratory incubation versus in situ hypolimnetic phosphorus accumulation1

Phosphorus release rates from anoxic sediments were determined from laboratory incubations of minimally disturbed sediment cores from seven lakes. These release rates were multiplied by an “anoxic factor,” based on the area and duration of hypolimnetic anoxia, to estimate internal phosphorus load. Despite individual variation, the experimentally derived internal loads were not significantly different from internal loads determined from hypolimnetic phosphorus increases at the end of summer stratification, except at internal loads <50 mg m−2 yr−1. Therefore, laboratory release rates can help predict internal loads after lake conditions have changed, e.g. after in-lake restoration measures.