Robin H. Nesbeda, Colby College

Date of Award

2004

Document Type

Honors Thesis (Open Access)

Department

Colby College. Geology Dept.

Advisor(s)

Donald B. Allen

Second Advisor

Robert A. Gastaldo

Third Advisor

Jennifer D. Shosa

Abstract

The present study focuses on East Pond, the head of the lake-chain system. East Pond is roughly oval in shape with several coves along the margins; it has an average 3 depth of 4.5 m, a maximum depth of 7.3 m, and a total volume of 26.35 x 10 6 m . The lake is surrounded by North temperate hardwood forest and a marshy outlet to the other lakes exists in the northwest comer. East Pond has suffered severe yearly algal blooms during the late summer and into the fall since 1993. This project aims to develop a baseline for the geological, geochemical, and hydrochemical parameters through spatial and temporal scales to better understand the lake's dynamics. It is suspected that changes in water chemistry over the summer may prohibit or promote phosphorus release from the lake bottom, leading to the observed algal bloom. Analyses included: characterization of the lake-bottom sediments, measurement of water-ehemistry parameters, and water-quality monitoring throughout the summer. Sediment analysis revealed a substrate that is characterized as an organic rich (mean TOC = 5.42%), moderately well sorted silt (mean grain-size = 4.51). Total phosphorus concentration in the sediments was elevated with a mean of 0.048%. Total phosphorus concentration in the water column during the algal bloom peaked at 64 ppb at 1.5 m depth. The basin morphology and coincidental orientation to local winds explain the sediment distribution and vertical mixing of the water column that released sediment phosphorus to the lake surface, leading to the worst algal bloom recorded in the lake's history.

Keywords

Watershed management -- Maine -- Somerset County -- East Pond region, Sedimentology, Geochemistry, East Pond Watershed (Me.)

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