Phosphorus Input and Its Consequences for Phytoplankton Standing Crop and Production in the Experimental Lakes Area and in Similar Lakes

Abstract

Correlation and regression analyses were used to assess several expressions for phosphorus loading, with and without corrections for water renewal and sedimentation, as predictors of total phosphorus concentration, chlorophyll, phytoplankton volume, and phytoplankton production in the Experimental Lakes Area (ELA) lakes. All expressions tested were good predictors, allowing predictions of the above parameters with 95% confidence intervals of 20–30% of the mean for any loading value. In general, correction for water renewal improved the fit of the expression, but correction for sedimentation did not. When the above strategy was applied to lakes outside ELA but with Shield or Shield-like drainage, good results were also obtained when expressions incorporating water renewal were used. If uncorrected for water renewal, loading was a poor predictor. Correction for sedimentation did not improve the expressions significantly. Correction for rapid changes in phosphorus input did not improve the predictability of equations, indicating that the equilibrium between ELA lakes and new loading conditions occurs very rapidly. Key words: Precambrian Shield lakes, eutrophication, lake management, nutrient inputs