Acute inhibition of bacterial growth in coastal seawater amended with crude oils with varied photoreactivities

Abstract

The increased potential for contamination of seawater by crude oils requires studies of bacterial biodegradation potential, but little is known of the differential negative impacts of oils on bacterial growth. No two wells generate chemically identical oils; and importantly, solar exposure of crude oil may differentially affect the bacterial response. Elucidating the role that sunlight plays on the potential toxicity of spilled crude oils is imperative to understanding how oil spills might affect microbes in the tropical and subtropical waters of Florida. This study examined light exposure of six different crude oils, and subsequent microbial responses to altered oils. Marine bacterioplankton heterotrophic activities were measured via3H-leucine incorporation after the addition of oils’ water accommodated fractions (WAFs) that were created under varied solar conditions. Inhibition of production increased with higher concentrations of WAFs, but dose-response trends varied among the oils. Increased solar exposure during WAF preparation generally led to more inhibition, but trends varied among oils. WAFs were also prepared under different parts of the solar spectrum. Solar-irradiated WAFs resulted in significant but variable acute toxicity vs. dark counterparts. Solar-induced toxicity was primarily a result of visible and not ultraviolet light exposure. Results indicate responses to oil spills are highly 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 photochemical changes and oil source in modulating microbial activity and bioremediation potential.

Clarifying the murk: unveiling bacterial dynamics in response to crude oil pollution, Corexit-dispersant, and natural sunlight in the Gulf of Mexico

“…For each dataset consisting of dark or sunlight-exposed variants for seawater controls, other condition variables included oil-only treatments, dispersant-only treatments, and combined oil and dispersant treatments. A Water Accommodated Fraction (WAF) was prepared using Macondo oil, a light crude oil also known by its well designation MC-252 surrogate (from the Deepwater Horizon oil spill), at a concentration of 1%, with sterile seawater as previously described (Headrick et al, 2023). This WAF was subsequently added to the mesocosms treated with oil.…”