LATE HOLOCENE ENVIRONMENTAL VARIABILITY AS RECORDED IN THE SEDIMENT OF A NORTHEASTERN OHIO KETTLE LAKE

Lake sediment can provide records of past changes in climate, water budget and lake level, ecosystems, and human impacts to the environment. This study uses the sediment from Brady Lake, a kettle lake in northeastern Ohio, to determine Late Holocene natural and anthropogenic environmental variability. Because no bathymetric map of the lake existed, one was created in ArcMap by collecting 7,507 latitude, longitude, and water depth measurements with a Garmen 125 fathometer and GPS unit. Sediment dispersal processes were studied by collecting surface samples throughout Brady Lake. Dense sandy sediment having low organic content (<5%) were present in water less than 2 m deep. Low density, porous muds having high organic content (30%) accumulate below 2 m due to sediment focusing. A 4.13-m-long Livingston piston core was collected from the central deep water basin to evaluate approximately 3,000 years of environmental change. Between 4.13 and 1.9 m core depth, low density gyttja having 70% organic content and a C/N ratio of ~13.7 is present. These sediment characteristics are interpreted as the pre-Euro American settlement period when the watershed was forested and sediment yield was low. However, within this interval an 18-cm thick layer of light brown gyttja with higher C/N ratio (17.4) may correspond to changing watershed conditions and an increase input of terrigenous sediment. At 1.9 m core depth, the gyttja abruptly changes to bedded mud having increased concentrations of Pb, Cu, Zn, and Cr interpreted as the onset of Euro-American settlement in 1805. Further impacts occur with the construction of the Pennsylvania and Ohio Canal in 1840 when the level of Brady Lake was raised in order to provide a source of canal water. Between 0.85 and 0.20 m core depth, black mud having high ferrimagnetic content and Pb concentrations up to 302 µg/g reflects increased anthropogenic impacts. This core interval may correspond to the presence of a major lakeside amusement park from 1891 to 1960. In the upper 0.2 m, Pb, Cu, Zn and Cr concentrations decline likely due to the closure of the amusement park and the enactment of environmental regulations.