22-4 A Preliminary Analysis of Modern and Historic Diatom Assemblages from Buckeye Lake, Ohio, USA

Abstract:

Ohio’s lakes are important economic, recreational, and cultural hubs; however, they are subjected to harmful pollutants such as nutrient inputs from agricultural runoff, which have a drastic impact on the water quality and health of lacustrine ecosystems. Buckeye Lake, Ohio’s oldest manmade reservoir, is a prime example of the ways in which nutrient pollution impacts the health of lake ecosystems and communities that depend on them. Over the past few decades, total phosphorus (TP) concentrations have been elevated enough for the lake to experience hypereutrophic conditions. Resultant blooms of microcystin (a harmful algae) have reached dangerous levels during the summer months, shutting down recreational areas. Examining environmental proxies helps inform the local community’s nutrient management strategies. Here, we examine past water quality of Buckeye Lake by assessing changes in diatom assemblages through the retrieval and analysis of a lacustrine sediment core. Many species of diatom prefer highly specific ranges of water quality parameters (e.g., pH and TP); as such, changes in their relative abundance (RA) in death assemblages can reflect past changes in these parameters.   

To examine the modern diatom assemblage of Buckeye Lake, sediment samples were collected from the top ~1 cm of the sediment surface using either an Eckman dredge or gravity corer. Additionally, to examine historical diatom assemblages, a sediment core was collected using a Bolivia piston corer. Diatom RAs will be determined through counting and imaging ~500 diatom valves (half-shells) from modern samples, and ~300 subfossil valves from each core sample. Based on previous analyses of modern diatom assemblages from other hypereutrophic manmade reservoirs in the same ecoregion as Buckeye Lake, we expect the modern/core-top assemblage of the lake to be dominated by species in the genera  Aulacoseira (e.g., A. ambigua and A. subarctica) and Discostella (e.g., D. stelligera and D. pseudostelligera). Throughout the sediment core samples, we expect to see an increase in the RAs of diatoms that prefer eutrophic conditions, such as small species in the genus Stephanodiscus (e.g., S. parvus and S. hantzschii). The results of this research will be shared with our community partner, Buckeye Lake for Tomorrow, who will integrate information about baseline nutrient states into their environmental management strategy. 

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