SPATIAL VARIABILITY OF SEDIMENT PHOSPHORUS FRACTIONS IN EUTROPHIC SHALLOW LAKES

The flux of phosphorus between lake sediments and the overlying water, termed internal loading, contributes to lake nutrient budgets and may fuel harmful algal blooms in some ecosystems. The release of phosphorus from the sediments is both biologically and physically controlled and the mechanisms controlling internal loading remain an active area of research. However, limnologists are still unable to confidently predict the hot spots and hot moments of internal loading in shallow lakes nor the resultant biological consequences of that phosphorus release.

In order to begin addressing the questions of "when and where" internal loading occurs, we examined the spatial heterogeneity of sediment phosphorus in three shallow eutrophic lakes. We found substantial spatial variation in sediment phosphorus fractions in all three lakes including up to a seven-fold difference in total sediment phosphorus in one lake. The spatial variation in phosphorus concentrations was not related to morphological features. The large spatial variability in sediment phosphorus fractions indicates the potential for significant hot spots of internal loading in shallow eutrophic lakes. This quantitative and spatially-explicit understanding of internal phosphorus loading potential can inform more effective eutrophication management.