Can microbes break down oil washed onto Gulf beaches?

the sand affects the microbial community and degradation of buried oil,” Huettel said.

Currents and winds carry the oil, and oil combined with dispersants — chemicals that disperse the crude into very small oil droplets — to the Gulf shores, where it washes up on sandy beaches. Larger crude-oil accumulations such as pancake oil (round, flat accumulations of heavy crude oil), and tar balls (weathered crude oil accumulations that have been formed into ball-shaped structures) are deposited on the beach. Meanwhile, liquid oil (in the form of an oil sheen, or small dispersed droplets) can penetrate many feet deep into the permeable beach sand.

“Oil-filled water that washes up on the beach filters through the porous sediment and carries the oil with it into the sand,” Huettel said. “In addition, the water-level drop between high and low tide causes a water-level drop within the beach sediment that can transport oil that has penetrated into the beach into even deeper sediment layers.”

“Crude oil is a natural component that constantly seeps out of Gulf of Mexico sediments — obviously in much smaller quantities than those now caused by the drilling accident — so native microbes have evolved that consume this oil and thereby degrade it,” Kostka said. “These microorganisms include bacteria and also some microalgae that live in the water column and the sediments of the Gulf of Mexico.”

Kostka said oil accumulations deposited on the beach surface are easily removed by, for example, scraping off the top layer of sand. The oil components that penetrate into the sand, however, can only be removed by microbial degradation.

“If oxygen is present — as it is in the water and in the upper layers of the beach sand — the microbes decompose the oil aerobically (by using oxygen),” Kostka said. “This degradation process is much faster than the degradation under anaerobic conditions (when no oxygen is available), such as those found in deeper sediment layers of the beach. That’s why at the site of the Exxon Valdez oil spill in Alaska, oil can still be found deeply buried in the gravel beach sediments, because anaerobic microbial degradation is slow and, in Alaska, slower still because of the cold climate.”

“Unfortunately, said Huettel, “crude oil contains such harmful substances that even small amounts can kill fish larvae — which means that oil stored in deep layers of beach sediment present a potential source of toxins to near-shore waters and groundwater.”

Their NSF-funded study (“Rates and mechanisms controlling the degradation of crude oil from the MC252 spill in Gulf of Mexico beach sands”) is the latest of several collaborations between Huettel and Kostka that have examined organic matter transport and degradation in Gulf sands. The current project also contributes to the energy-related research that Kostka performs for Florida State University’s Institute for Energy Systems, Economics and Sustainability (IESES), which has been heavily involved in providing information and expert advice to Florida’s governor’s office and legislature regarding oil and gas development.

Kostka is an environmental microbiologist and microbial ecologist known for his studies of the services that microbes provide to humans and ecosystems. He serves as associate director for IESES, where he has developed and oversees an initiative he named SABER (Systems Approach to Bioenergy Research). A member of the Florida State faculty since 1999, Kostka has served since 2007 as the co-principal investigator of a five-year, $15 million grant from the U.S. Department of Energy for research on biologically mediated cleanup of radioactive waste from nuclear weapons production at U.S. DOE sites.

Huettel, a biological oceanographer, is an expert on biogeochemical processes in coastal sediments. Central themes of his research include the influence of hydrodynamics on organic matter degradation, oxygen dynamics and nutrient cycling in coastal sediments. Before joining the Florida State faculty in 2003, Huettel was research group leader at the Max Planck Institute for Marine Microbiology in Bremen, Germany.