Abstract:

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.

Suggested Citation:

K. Ramesh Reddy, Kanika Inglett. 2015. Temperature dependent degradation of oil-C in coastal wetland soils under aerobic conditions.. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N78S4MV0

Purpose:

Manipulative experiments in the lab on reference soil (not oil contaminated). Laboratory closed system experiments were done by adding weathered oil. Treatment conditions included low- and high-temperature incubations and measuring the respired-C (carbon dioxide). Stable isotope probing of soil organic matter and the respired carbon dioxide was done to determine the distribution of soil organic matter-C and oil-C utilized (in biomass and respired) by the microorganisms.

Data Parameters and Units:

Soil biogeochemical parameters (pH, soil moisture, Total C, Total N, isotope signatures of C and N), respiration rates, microbial biomass. TABLE1. Metal analyses of soils: Samples [A, B, C], reps, metal concentration(mg/kg) [Na, Mg, Al, Si, S, Cl, K, Ca, Mn, Fe, Co, Ni, Cu, Pb]. TABLE2. Basic biogeochemical analyses of soils: Samples [A, B, C], reps, LOI (%), Moisture (%), MBC (mg/kg), pH, Total Carbon (%), Total Nitrogen (%), Enzyme activity (mol/gdW[BGL BXY, CEL, NAG]. TABLE3. Averages of microcosm respiration analyses: Sample (number), Samples [A, B, C], [OILED, CONTROL, BLANK no-soil no oil, TRT-Temperature [HT high temperature = 28 degrees Celsius, LT low temperature = 18 degrees Celsius ], CDO Carbon Dioxide Respiration Rate (ugC/g dw soil/d), delta C 13 - CO3(per mil).

Individual Files: