FACTORS INFLUENCING HYDROCARBON DEGRADATION IN 3 FRESH-WATER LAKES

The mixed microbial flora of 3 lakes in Ohio [USA], with differing histories of hydrocarbon pollution was examined in relation to the ability to use hydrocarbons. Weathered kerosene was spiked with naphthalene, pristane, 1,13-tetradecadiene,and n-hexadecane and added to water-sediment mixtures from the 3 lakes, and utilization of the 4 marker hydrocarbons was measured. Each of the marker hydrocarbons was metabolized; naphthalene was the most readily used and pristane was the most resistant. Values for dissolved O2 suggest that O2 did not limit hydrocarbon degradation in the water column at any site examined. Nutrient addition studies indicated that N and P limited hydrocarbon degradation at all sites examined. Maximum numbers of heterotrophic bacteria were detected when the water temperature was .gtoreq. 10.degree. C. The data indicate that temperature limits hydrocarbon degradation in the winter, except at a site which had been impacted by an oil spill and which received chronic inputs of hydrocarbons and nutrients. In samples from that site, all 4 marker hydrocarbons were degraded at 0.degree. C. Results of temperature and nutrient-addition experiments suggest that different seasonal populations of hydrocarbon users are selected at that site, but not at other lake sites.