Effect Of Temperature On Utilization Of Oil Derived C In Coastal Wetland Soils Under Aerobic Conditions.

Coastal marsh soils may be exposed to weathered crude oil in the event of an oil spill. Certain fractions of this oil may serve as labile carbon sources for the microbial communities present in these soils, thereby, altering various biogeochemical processes, specifically carbon flow. As temperature is a major regulator of biogeochemical cycling of nutrients, this study was designed to understand its influence on carbon flow and microbial metabolic functions in coastal marsh soils in the presence of oil under aerobic conditions. Several parameters were assessed over the course of this laboratory manipulation study. Treated oiled samples and oil free controls were held under aerobic conditions at two different temperatures (18°C and 28°C). Headspace CO₂ was used to determine the rates of microbial respiration. The isotopic δ¹³C signatures were used to determine the microbial utilization of carbon from oil and from soil organic matter. Activities of several hydrolytic C enzymes were determined using fluorometric analysis to determine changes in metabolic functions. Based on the results, this study suggests that different fractions of soil carbon are utilized under low and high temperature conditions. The rates of CO₂ respiration were higher at higher temperature and do not appear to be significantly affected by the presence of oil relative to the control samples. The data obtained from the isotopic analyses also appear to suggest that temperature is the major factor in determining which fraction of C is utilized from the soil rather than the presence of oil.