PREDICTED VERSUS ACTUAL DETERMINATIONS OF ALGAL PRODUCTION, ALGAL BIOMASS, AND ZOOPLANKTON BIOMASS IN A HYPEREUTROPHIC, HYPOSALINE PRAIRIE LAKE

We compared the accuracy of various regression models in predicting al gal production, algal biomass and composition, and zooplankton biomass in a hypereutrophic, hyposaline prairie lake. The total phosphorus (T P) models investigated underestimated mean summer algal biomass and in edible biomass: the models overestimated mean summer edible algae biom ass and annual primary production in the euphotic zone. Differences be tween predicted and actual biomass values are attributed to intense zo oplankton grazing on the edible algal community and to the gradual acc umulation of slow-growing, inedible algae. The TP model investigated p rovided an accurate prediction of zooplankton biomass. The algal bioma ss model overestimated zooplankton biomass, possibly because edible al gae accounted for a very small fraction of algal biomass in Humboldt L ake during the ice-free season. The chlorophyll model investigated und erestimated zooplankton biomass, apparently because Humboldt Lake alga e have a relatively low chlorophyll content. The use of a 0.01 convers ion factor to estimate algal biomass on the basis of chlorophyll appea rs to be inadequate and requires further study. There was no evidence that hyposaline Humboldt Lake has a relatively high zooplankton to phy toplankton biomass ratio when compared with freshwater lakes.