| Abstrakt: |
A phytoplankton simulation model was previously developed and calibrated to an extensive set of baseline data for 1974 and 1975 on Saginaw Bay, Lake Huron. Comparisons are made between a priori model predictions and an extensive set of resurvey data acquired in 1980, subsequent to the implementation of controls on phosphorus loadings. The response of the bay is consistent with trends of model prediction ranges, but not with their absolute values in all cases. Observations are consistent with the prediction that threshold odor violations in the municipal water supply would be eliminated with total phosphorus tributary loadings that occurred in 1980. Model predictions are consistent with the observations that total phosphorus concentration decreased by a much smaller proportion than the decrease in tributary loadings, and that phytoplankton concentrations, especially blue‐greens, decreased by larger proportions than total phosphorus concentrations. Wind‐induced sediment resuspension appeared to be responsible for discrepancies that occur between model results and field data for total phosphorus concentrations, and for the relative lack of response of these concentrations. Discrepancies that occur for phytoplankton appear to be due, in part, to significant changes in the phytoplankton community structure. Model results suggest that changes in environmental conditions are important in determining the response of the bay, independent of any effects due to reductions in phosphorus loadings. |
