PRELIMINARY ANALYSIS AND PALEOENVIRONMENTAL ASSESSMENT OF THE SPONGES AND DIATOMS PRESERVED IN A LATE HOLOCENE TO RECENT SEDIMENT CORE FROM BROWN’S LAKE, WAYNE COUNTY, OHIO

A 1.5-meter sediment core taken from Brown’s Lake, a kettle lake near Shreve, Ohio and dated with Pb-210 and C-14 records changes in climate, ecology, and sedimentation through the last 2000 years. The most notable observation is the significant increase in silty wind-blown sediments indicating the beginning of anthropogenic activities, including European-American upland deforestation and other land use changes in the area at the beginning of the 19th century. Below this sequence is a peat and loess mixture where sedimentation rates and organic debris increase drastically. The bottom of this core is dated by radiocarbon to between 1430 – 1530 CE. Microfossils in the form of siliceous sponge spicules and diatom frustules were collected and analyzed to measure population dynamics through time as well as to infer ecological changes in the lake. Using the wet oxidation method to remove organic material from samples, 3 genera of freshwater sponge (Racekilea, Heteromeyenia, Anheteromeyenia) have been identified based on the morphology of their spicules via light microscopy. Marked changes were noted however, further research is needed to infer what environmental conditions are indicated by the presence or absence of their remains. Seventeen diatom genera were recorded in the core, and the eight most prominent (Eunotia, Tabellaria, Cyclotella, Lindavia, Discostella, Gomphonema, Stauroneis, Navicula) were counted at 5cm intervals on smear slides. We found spikes and dips in diatom populations that suggest periods of warming and cooling that affected these organisms. Preliminary results and dating suggest that these organisms exhibit population changes that align with warming and cooling events of the late Holocene such as the Little Ice Age, Medieval Warming, the Late Antique Little Ice Age, and possibly the Roman Warming Period, as the bottom of the core dates back to around 2 kya.