IN-SITU ANALYSIS OF HYDRODYNAMICS AND SEDIMENT DYNAMICS IN MISSISQUOI BAY, LAKE CHAMPLAIN

The relationship between circulation currents, suspended sediment concentration, and sedimentation rates were investigated as part of a larger 5-year project studying the causes of eutrophication in Missisquoi Bay, a shallow bay (4 m) in Lake Champlain (Vermont and Quebec). Previous studies collected hydrodynamic modeling was based on a single month of ADCP data in the western arm of Missisquoi Bay and cores were taken from only the southeastern area. This study looks at the first 2 months of currents, wind forcing, and water level variations at five sites to better understand sediment resuspension and deposition. North-south and east-west centimeter-scale diurnal oscillations of lake level were observed and were not linked to the calculated ~30 minute surface seiche. Currents were obtained from Acoustic Doppler Current Profilers (ADCPs) indicate that after consistent wind forcing, both cyclonic and anticyclonic circulation patterns were set up. Unique to this very shallow bay was the degree of directional shear (in depth) as high as 180 degrees. Sediment properties and magnetic susceptibility measurements of five push cores vary, indicating that sedimentation rate is not constant throughout the bay. Implications of our results will provide other investigators insight into how phosphorus and nitrogen are being moved throughout the bay.