Seasonal diatom community responses to development and climate change in Lake George, an oligotrophic lake in the Adirondack Mountains

Lake George is a highly monitored, oligotrophic lake that experiences widespread tourism in the summer months. The southern basin has more shoreline development than the northern basin, resulting in a south to north gradient of anthropogenic impairment. This study aimed to assess differences in nearshore diatom communities regarding gradients of water chemistry and watershed development throughout the lake. Using redundancy analyses, water chemistry explained more variation within diatom assemblages than watershed variables. Seasonal comparisons of watershed types, based on development, revealed SPC values to be significantly higher in the southern basin in all three seasons (spring, summer, and autumn). Among the three seasons, summer demonstrated the best potential for further monitoring of diatom communities with the north and south basins demonstrating differences in Shannon–Weiner (H′) diversity index values and proportions of Asterionella formosa, Fragilaria crotonensis, and Lindavia lemanensis. Dominant diatoms from previous studies in the lake were compared to present populations and showed a concomitant reduction in Stephanodicus spp. and Melosira spp. while smaller centric species continue to increase. Given the differences between the two basins, climate change is likely to manifest differently in the southern, more productive basin than the northern basin.