SEDIMENT CHARACTERISTICS OF MESSALONSKEE LAKE, BELGRADE LAKES REGION, CENTRAL MAINE

Messalonskee Lake is the result of glacial meltwater processes following the most recent deglaciation. The lake is supplied by Belgrade Stream that enters on the southwestern end and discharges through Messalonskee Stream on the northeast to the Kennebec River. Public concern about nutrient loading of the watershed has resulted in preliminary investigations conducted in the early 1990s. The present study investigated the lake’s sedimentology to characterize grain-size, total organic carbon (TOC), and total organic nitrogen (TON) distributional patterns. Two vibracores were extracted from the wetlands adjacent to Belgrade Stream and 56 bottom-grab samples were collected across several lake transects. Analyses included standard sieving, Spectrex laser particle size analysis (<63μm), TOC and TON using an Exeter 440 CHNO instrument. Overall, the lake is characterized by fine sand and coarse silt (Average median 4Φ), with median grain size ranging from medium sand (1Φ) where Belgrade Stream discharges into the lake to medium silt (6.3 Φ) towards the lake center. There is a significant absence of clay-sized sediment in the sample suite. Coarser sediment is found on the western margin. TOC averages 6.0%, with values ranging from 0.2-13.2%. TOC:TON ratios indicate that most organic matteris mixed algal and terrestrial in origin. There is no statistical relationship between grain-size and percent TOC data. The sediment-distribution pattern fines along the length of the lake towards the northeast, but coarser clasts along the western margin are thought to have been introduced through anthropogenic development of the area. The lake’s high TOC values is the result of sediment starvation and terrestrial contribution that has loaded the system over time. Decomposition of terrestrial OM has contributed to the available nutrients for algal growth, resulting in the TOC:TON character of present bottom sediments.