A HISTORIC SEDIMENT RECORD OF LANDSCAPE DISTURBANCE AROUND EDINBORO LAKE, NORTHWESTERN PENNSYLVANIA

Lakes are vulnerable to changes within the watershed, especially those that increase sediment and nutrient influx. Effective watershed management requires a means of evaluating the impact of these changes from multiple sources. Presented here is an analysis of the impact of human settlement on the sedimentation history of Edinboro Lake, a small kettle lake in Erie County, Pennsylvania, adjacent to the town of Edinboro.

Sedimentation history was investigated with Livingston cores taken from the deepest (27ft) portion of the lake. Bulk density, percent organic matter (LOI), and magnetic susceptibility were measured at 2 cm intervals from split cores. Pb²¹⁰ and Cesium data were obtained from a separate core, taken in close proximity to those in this study. Samples for dating were taken at 4 cm intervals to constrain sediment age. Mass accumulation rates were calculated using these dates.

Core data was compared to the history of human activities within the watershed. Results show a steady increasing trend in the mass accumulation rate from 1855 to present by about 2mg/cm²/yr, likely related to increasing human development in the watershed. A considerable increase in bulk density between 1920-1940 parallels a historic period of shore-adjacent subdivision, clearing, and construction of the Lakeside community, likely generating high bulk density runoff. Two dramatic spikes in sedimentation are clearly correlated with two large dredging operations around the edges of the lake. The first dredging operation occurred c.1955 and channelized large swaths of the wetland at the lake’s north end. Sedimentation during this time reflects the low bulk density and high organic content of the disturbed peat. Wetland removal allowed allochthonous clastics from soil runoff to enter the lake. The second dredging occurred between 1989-1994 to control weeds and remove sediment around the perimeter of the lake. High bulk density and low organic content within this time frame suggests disturbance of the underlying glacial clastic sediment not encountered during earlier dredging. Increases in magnetic susceptibility accompanying the Lakeside development and following the c.1955 channeling at the north end of the lake are associated with increases in bulk density, the product of eroded soil from the watershed.