DRIVERS OF PHOSPHORUS PARTITIONING AT THE SEDIMENT-WATER INTERFACE OF TWO SHALLOW EUTROPHIC VERMONT LAKES

In shallow lake systems, phosphorus (P) availability to water column algal populations is often controlled by the release (internal loading) or sequestration of P in lake sediment. This study aims to provide novel insight into feedbacks between watershed-lake physical configurations, seasonal variability in weather and biological productivity, and the chemical partitioning of P in lake sediment. To accomplish this, time series sediment geochemical extractions with concurrent water column physical and biogeochemical monitoring will be analyzed to examine the relationship between water column dynamics and P partitioning of near-surface sediments in two shallow, intensively-monitored eutrophic systems. Each system experiences internal loading of P that produces severe recurring cyanobacteria blooms, but previous work suggests that their different physical configuration (bathymetry, surface area, watershed-lake area) impacts the composition and behavior of P in their respective sediment and water columns. As such, this work will test hypotheses around how the chemistry of concurrent sediment P pools evolves across the seasons in three systems that 1) suffer from the same pollution problem, 2) are exposed to the same weather, but 3) differ fundamentally in their physical configuration. Ultimately, this will improve our conceptual model of the physical, chemical and biological drivers of internal loading or sequestration of sediment P pools across time and space in shallow freshwater systems, with widespread applicability to understanding the global water quality issue of eutrophication.