State Water Resources Research Institute Program

Project ID: 2007CT134B
Title: The Geochemical Record of Cultural Eutrophication in Sediments of Beseck Lake and Lake Waramaug, Connecticut: Implications for Nutrient Cycling and Remediation Efforts
Project Type: Research
Start Date: 6/ 1/2007
End Date: 5/31/2009
Congressional District: 3
Focus Categories: Geochemical Processes, Sediments, Nutrients
Keywords: eutrophication, sedimentary record, paleoredox, paleoproductivity
Principal Investigator: Ku, Timothy (Wesleyan University)
Federal Funds: $ 2,600
Non-Federal Matching Funds: $ 27,727
Abstract: Cultural eutrophication is the process whereby human activity increases the amount of nutrients entering an aquatic ecosystem causing excessive biological growth and depletion of dissolved oxygen concentrations. Successful restoration or management policies of impaired water bodies must set realistic water quality goals. We propose to examine the cultural eutrophication history of two Connecticut lakes, Beseck Lake and Lake Waramaug, which have been the focus of significant remediation efforts. Recently, residences surrounding Beseck Lake were converted from septic systems to a city sewer line and Lake Waramaug has been the site of many remediation efforts since the early 1980s, including the installation of two in-lake aeration systems. Continuous lake monitoring since the late 1970s has shown an improvement in lake conditions.

Lake sediments record the past conditions and processes in lake basins, thus we can determine pristine water conditions prior to human disturbance and document the progression and decline of cultural eutrophication. Sediment freeze cores collected from Beseck Lake and Lake Waramaug contain remarkably well-preserved, sedimentary facies and bioturbation structures that represent the last ~100-300 years of lake history. Both of these lakes are seasonally anoxic and currently deposit organic-rich black mud in the summer though water conditions have clearly changed in the last century as indicated by fluctuating organic carbon concentrations, Fe/Al and C/N ratios, and redox-sensitive trace element (U, V) concentrations. These initial results establish that Beseck Lake and Lake Waramaug sediments record the history of these lakes prior to significant human impact, during the onset and peak of cultural eutrophication, and throughout the current remediation efforts. We propose to build a detailed history of Beseck Lake and Lake Waramaug with two main objectives: 1) determine the source(s) and accumulation rates of sedimentary organic carbon, organic nitrogen, and detrital minerals, and 2) determine the paleoredox level of the lake by examining the size distribution of framboidal pyrite and by comparing redox-sensitive elemental concentrations to present-day sediments overlain by oxic or anoxic waters.

The results of this work will provide local and state governing agencies with a long-term reference example with which to compare future remediation strategies. This study also employs several analytical techniques that have not been fully explored in freshwater sedimentary systems and we expect that this work will lead to future advances in scientific methodology.

Progress/Completion Report, PDF

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