Phosphorus Pool Sizes and Fluxes in the Epilinnnion of a Mesotrophic Lake

Abstract

A plausible budget for phosphorus fluxes between different size/functional groups was constructed for the early summer epilimnetic plankton of Jacks Lake, Ontario. Consideration of the complex interactions at the base of the food web, particularly the ability of nanoplankton to graze on picoplankton, helped to resolve the question of phosphate uptake by bacteria versus algae. While the concentration of phosphate we estimated with column chromatography was lower than chemical detection limits, it was still too high to reconcile with our other measurements and we conclude that actual phosphate concentrations may be less than 1 nM. Some microplankton were shown to liberate dissolved phosphate and organic phosphorus when lake water is filtered. The phosphorus content and turnover of major ciliate, rotifer, and crustacean zooplankton were determined and the importance of these compartments as phosphorus sources and sinks was included in the epilimnetic model.