EVALUATING POTENTIAL FOR WATER QUALITY DECLINE IN MAINE LAKES

Understanding lake vulnerability with respect to eutrophication and loss of water quality is important in a changing chemical and physical environment. This project aims to identify and measure physiochemical characteristics that make lakes vulnerable to external stresses including regional warming and land use changes. We hypothesize that sediment chemistry, lake morphology, water temperature distribution, and percent agriculture control phosphorus (P) concentration, and hence, lake water quality.

We studied 24 lakes in Maine covering a wide range of trophic state. Water samples were collected twice (June and August) in 2015, and analyzed for a suite of elements, with a focus on P. Short sediment cores, collected in June 2015, were sequentially extracted and analyzed for P, aluminum (Al) and iron (Fe) in different fractions. The results show that lakes whose sediment has a NaOH-extractable Al to dithionite-reducible Fe ratio (Al(_NaOH+BD):Fe(_NaOH+BD) ratio) > 3 are less susceptible to internal P release. Likewise, lakes that stratify strongly during the summer have lower epilimnetic P concentrations. Among other factors, lakes that are susceptible to internal P release are those with sediment Al(_NaOH+BD):Fe(_NaOH+BD) ratio < 3, and those that stratify weakly during the summer. Identifying and quantifying factors that lead to lake eutrophication allow us to classify susceptible lakes and inform the stakeholders, such as lake residents and policy makers, with respect to best practices for lake stewardship.