Characteristics of Lake Sediments Across a Submerged Valley, Andover Lake, CT. abstract by Heath Carlson.
This study examines physical and chemical characteristics of lake sediment in Andover Lake, Connecticut, an artificial water body that was dammed in 1927. In particular, I examine the spatial variability of phosphorus in the lake sediments in relation to changing water depth, location in the lake, and pre-existing conditions along a controlled transect across the lake. Phosphorus is an important nutrient that contributes to lake eutrophication processes. Three distinct sedimentary units occur within seven-piston core and three percussion core. Lowermost and oldest Unit I only consists of coarse-grained sediments, with mottled colors, and large quartz fragments, and is interpreted as a submerged soil horizon that formed prior to the damming of the lake. Unit II ranges in thickness from 6-43 cm, consists of organic rich, silty sediment and contains woody and fibrous debris. This unit is interpreted as a transitional deposit laid down following lake damming as the lake levels rose. Unit III consists of 4.5-33cm of organic-rich, fine-grained lake sediment. Analyses of surface grab samples (n=15) indicate that TP (by wet weight) is 2000-7500 times higher in unit III than in 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 moisture, moderate for organic carbon, and are not significant for TP, Fe, and inorganic carbon. These results indicate that mixing of the lake sediment will likely introduce TP into the water column and may contribute to lake eutrophication.