Biogeochemical model for the eutrophication of East Pond, Maine

Bernadette Bibber

Document Type Dissertation/Thesis


East Pond, a mesotrophic lake in Smithfield, Maine has been experiencing increasing algal blooms since 1975. The Maine DEP, Colby College, and the University of Maine have attributed nutrient inputs from the surrounding lake properties, internal nutrient loading from the sediments, and overgrazing of zooplankton by planktivorous fish as potential causes of the East Pond algal blooms. This project explores the role of physical forcing such as wind speed, sunlight, and water clarity on lake stratification and mixing in the context of internal nutrient loading to East Pond. Through studying the biogeochemical processes in East Pond, the Secchi depth and the influence of light penetration on stratification of the lake was found to be one of the major driving forces of eutrophication. Spring Secchi depth determines the lake stratification by regulating the depth distribution of solar energy throughout the water column. The presence of a deep Seccru depth allows uniform heating throughout the water column that prevents stratification. Conversely, a shallow spring Secchi depth traps heat at the surface, stratifies the water column, mixing is prevented, and the hypolimnion becomes anoxic releasing sediment based nutrients. These nutrients are then available to algae after the lake remixes in early to mid August.