SPATIAL VARIABILITY OF TOTAL PHOSPHOROUS IN LAKE SEDIMENT, ANDOVER LAKE, CT

This study examines the spatial variability of total phosphorus (TP) and related variables (moisture, organic, inorganic carbon, Fe) in sediment in Andover Lake, Connecticut, an artificial water body dammed in 1927. Three sedimentary units occur within seven-piston core and three percussion core collected along a tightly controlled lake-wide transect. Lowermost sandy and mottled sediments (Unit I) are interpreted as pre-lake soils and are sharply overlain by mixed organic-rich silty sediment (Unit II, 6-43 cm thick) that contains fibrous woody debris deposited as the lake flooded. Unit III (4.5-33cm thick) lacks wood fragments and is characteristic of modern lake deposition (gyttja). Analyses of surface grab samples (n=15) indicate that TP (by wet weight) is 2000-7500 times higher in unit III than the overlying water column. Comparison of means tests (n=21) indicate significant differences between units II and III for moisture, inorganic carbon, and Fe but not for organic carbon or TP. Trends in relation to water depth are strong for moisture, moderate for organic carbon, and are not significant for TP, Fe, and inorganic carbon. However, when adjusted for moisture content, TP shows a significant increase with water depth. These results suggest that mixing of lake bottom sediments will likely introduce TP to the water column and may contribute to lake eutrophication.