WATER QUALITY ANALYSIS AND SOURCES OF TOTAL COLIFORM AND E. COLI BACTERIA IN THE SENECA LAKE, NY, WATERSHED

Seneca Lake, the largest and deepest Finger Lake, is a Class AA drinking water supply for approximately 100,000 people in central New York. This study investigated the concentration of total coliform and Escherichia coli (E. coli) bacteria. The goal was to determine significant sources of bacterial contamination within the watershed resulting from, for example, septic systems, sewage treatment plants and human or animal feces. The watershed is an ideal natural laboratory to study the biological integrity because its 29 subwatersheds drain a variety of land use activities, on-site treatment systems and other potential sources of bacterial contamination.

Seven primary streams, nineteen streams in all, four lake sites and twelve nearshore lake sites were sampled during the summer months over a two year period (2003-2004). Water samples were collected in sterile bags and kept cold until analysis in the lab using Hach’s m-ColiBlue24 broth filtration technique (CPU/100mL). Standard water quality tests were measured on site, including pH, conductivity, and temperature using Oakton handheld meters; chloride, hardness, and alkalinity concentrations using LaMotte student titration kits. Water samples were also collected and filtered through a pre-weighted 0.45 micron filter for total suspended solids, and the filtrate was analyzed for dissolved nutrient concentrations (phosphate, nitrate and silica) by spectrophotometer, and major ion concentrations by ion chromatograph.

Total coliform and E. coli bacteria concentrations were typically well below the EPA maximum contaminant levels (MCL’s) for Class A drinking water (2400 CFU/100mL for total coliform and 235 CFUs/100mL for E. coli). Lake samples were typically ten times less concentrated than stream water, and lacked any temporal or spatial trends. Wilson and Hector Falls, regularly had higher bacteria concentrations than the other streams, suggesting higher bacterial inputs from larger amounts of agricultural land and septic systems, respectively, than the other subwatersheds. The bacteria concentrations did not correlate with nutrient concentrations or other measured parameters. This study suggests that agriculture and septic system sources pose potential but not detrimental impacts on the bacterial integrity of the Seneca Lake watershed.