Comparison of microbial growth and community structure in response to different crude oils with varying photoreactivity

Wade H Jeffrey1, Melissa Ederington-Hagy2, Lisa Nigro3, Arianna L Simmering4 and Erika L Headrick4, (1)University of West Florida, Department of Biology, Pensacola, FL, United States, (2)University of West Florida, Center for Environmental Diagnostics and Bioremediation, Pensacola, United States, (3)University of West Florida, Center for Environmental Diagnostics and Bioremediation, Pensacola, FL, United States, (4)University of West Florida, Center for Environmental Diagnostics & Bioremediation, Pensacola, FL, United States
Abstract:
Investigations of the relationships between crude oil and bacterioplankton have provided clues into how crude oil constituents are degraded, and how anthropogenic spills affect system nutrient cycling and food webs. Some studies have indicated that this relationship changes when crude oil is exposed to solar irradiance. Oils are complex mixtures of hydrocarbons and other elements, yet there is minimal information regarding a direct comparison of different crude oils under varying solar exposure and corresponding biological responses. The acute and longer-term biological effects of solar-exposed crude oil from six Gulf of Mexico wells and one oil from Wisconsin were investigated. Coastal seawater samples were amended with irradiated and non-irradiated water accommodated fractions (WAFs) of crude oil to be analyzed for acute inhibition, longer-term growth patterns and microbial diversity. The oil sample from the Wisconsin well yielded significant differences from the Gulf of Mexico-derived treatments in all aspects of our study. Two of the Gulf of Mexico oils showed greater acute toxicity when irradiated under photosynthetically active radiation (PAR) than under full sun (UV) conditions. Most oils produced greater acute toxicity from solar-exposed WAF treatments versus dark counterparts. When changes in the microbial diversity were examined in longer exposures, the WAFs that illicited the greatest growth inhibitory response also resulted in the greatest changes in bacterial community structure. Variability in known oil degrading bacterial groups also differed depending on the source oil. These results indicate that microbial responses to oil spills are dependent on the source of the oil, and solar conditions at the time and location of the spill. The data presented here demonstrate the importance of PAR in photochemical change, and the need to consider local environmental conditions and oil source when predicting oil spill effects.
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