USING MICROFOSSILS TO RECONSTRUCT WATER QUALITY HISTORY IN LAKE GEORGE, NY

Lake George, NY is a headwater lake with Class AA Special water quality rating, surrounded by forever wild forest, and is a valuable tourist destination. Lake monitoring reveals increasing anthropogenic impact over the past 30 yrs (Boylen et al. 2014). We conducted a multiproxy pilot study using microfossil assemblages (testate amoebae, ostracods, diatoms, pollen, and non-pollen palynomorphs-NPP) and stable isotopes (O, C) from 8 short cores and 13 Ekman grab samples to reconstruct anthropogenic influence on the lake (e.g., salt loading, eutrophication, pollution, temperature). We characterize modern assemblages and link their biotic variability to water-quality data.

Surface sediments yield high abundances of environmental-indicator testate amoebae taxa. Salt-tolerant Centropyxis aculeata “discoides” is abundant at Lake George Village (LGV), Tea Island (TI), Northwest Bay (NWB), and Bolton Landing (BL), illustrating a biotic response to road salt runoff. Arcella vulgaris, an indicator of extremely unfavorable conditions (Neville et al. 2010), is present only in areas near towns and developed areas (Warner Bay (WB), LGV, and BL). Difflugia protaeformis “claviformis”, an indicator of high organic phosphorus (OP ~150-450 ppm; Patterson et al. 2012), is most abundant at LGV and WB, likely reflecting nutrient runoff from fertilizer. Abundance of Cucurbitella tricuspis, associated with aquatic plant life and algal mats, is very high in WB (an area closely associated with wetlands), and is also high at West Brook, LGV, BL, and Hulett’s Landing, where invasive Myriophyllum spicatum (Eurasian watermilfoil) is abundant.

Pollen, Cs, and Pb profiles constrain sediment ages and mixing depth. Our modern testate amoebae assemblages, together with published records of testate amoebae, diatoms, pollen, and NPP, provide the means to interpret downcore assemblages. Increases in OP-tolerant difflugid strains of testate amoebae as well as high productivity diatoms and NPP in shallow-water cores at Paradise Bay, and potentially NWB and TI, suggest modern eutrophication in these areas. Preliminary results of the deep-water short core at Dome Island (~30 m water depth) may suggest strong bottom currents, indicated by sparse, low-diversity oxidation-resistant NPP and consistent testate amoebae assemblages.