EVALUATING POTENTIAL FOR WATER QUALITY DECLINE IN MAINE LAKES
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.