MULTI-PROXY ANALYSIS OF ORGANIC MATTER SEDIMENTATION IN THREE MAINE LAKES
The annual mass accumulation rate (MAR) of sediment from each lake was determined: CL: 7.63mg/cm2 yr, TP: 5.23mg/cm2yr and LL: 23.0mg/cm2yr of sediment accumulation. Organic Carbon (OC) MAR’s were calculated as 1.17 mg/cm2yr at CL and 1.02mg/cm2yr at TP. Analyses of δ13C vs. C/N data at CL and TP suggest a mix of aquatic and C3 land plant organic matter sources. δ15N for CL has a mean value of 6.26 which is much higher than TP (4.05‰) and LL (4.48‰). The heavier values found at CL suggest higher anthropogenic effects due to human and/or animal waste from the watershed.
Seasonal variability is also noted within each record. For instance, all three lakes show seasonal variability in organic matter characteristics, likely attributed to seasonal changes in productivity. In addition, LL exhibits a shift between winter and spring in δ15N and %N values suggesting that the flooding of the western branch of the Penobscot River during the spring season loaded nutrients into the system causing an increased productivity rate.