UNEARTHING THE EFFECTS OF EUROPEAN-AMERICAN SETTLEMENT ON A NORTHEAST OHIO KETTLE HOLE THROUGH DIATOM STRATIGRAPHY

Recently, wetland conservation has highlighted the necessity for measuring limnological changes in lakes and ponds following European-American settlement. Prior studies at Brown's Lake (kettle hole) in northeast Ohio identified a 25-cm thick 'anthropogenic' layer of silts and clays, interbedded between organic-rich muds, marking the time of settlement stratigraphically and representing intensive land clearing and tillage in Wayne and Holmes counties during the 1800s. In addition to stratigraphic sections, regional tree-ring records assist with dating settlement activities. However, the effects of settlement and limnological changes caused directly or indirectly by settlers are not well-understood. Diatoms respond to modifications in water quality and habitat parameters, and siliceous cell walls enable preservation in sediments as fossils. Thus, diatom stratigraphy can record the history of limnological changes. Two 1-m sediment cores from the kettle hole's center were extracted using a modified-Livingstone sampler. The cores were analyzed for lead-210 concentration, magnetic susceptibility, organic content, and diatom distribution. Lead-210 radiometric dating shows the anthropogenic layer was deposited before 1846. Magnetic susceptibility increased while organic content decreased during the layer's accumulation. An initial diatom study (200 cells) reveals non-motile and slightly motile genera (i.e., Cocconeis sp., Eunotia sp., Tabellaria sp., and various centric species) dominated before settlement. After settlement, however, motile genera (i.e., Gomphonema sp., Navicula sp., and Nitzschia sp.) dominated. Thus, this shift may be interpreted as a consequence of human-caused limnological alterations. Further diatom analyses will deepen understanding of Brown's Lake's limnological history and guide initiatives in restoring wetlands to their pre-settlement conditions.