Will the Gulf Sand Clean Itself?

Tar balls have landed on a beach in Galveston, Texas, meaning oil from the Gulf of Mexico spill has now hit all 5 Gulf states. It turns out that sand naturally cleans itself, but the Deepwater Horizon oil spill may be too much for it. Scientists are investigating how quickly the oil carried into Gulf of Mexico beach sands is being degraded by the sands’ natural microbial communities, and whether native oil-eating bacteria that wash ashore with the crude are helping or hindering that process.

Meanwhile, researchers aren’t convinced that the Texas oil that has drifted all the way from the BP spill. BBC News quotes a statement that says, “The testing found that the oil was lightly weathered, raising doubts that the oil traversed the Gulf from the spill source.” It could have dropped off one of the ships that regularly carry oil to Texas to be processed. BBC quotes Galveston mayor Joe Jaworski as saying, “This is good news. The water looks good. We’re cautiously optimistic this is an anomaly.”

Oceanographers Markus Huettel and Joel E. Kostka are trying to predict when most of the oil in the beaches will be gone by studying the speed of the oil degradation rate. This is not just vital information for the tourist industry, but it’s important because speed matters, since toxic crude components that remain buried on Gulf Coast beaches may start to seep into the groundwater below. They may be able to discover how to SPEED UP this natural cleaning process.

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. Huettel says, “This enormous oil spill affects hundreds of miles of beaches in the Gulf of Mexico. We can remove the oil from the beach surface, but oil is also carried deeper into the sand, and we need to understand what happens to that oil. Preventing groundwater contamination is crucial not only to Gulf Coast residents but also to coastal management and local economies like fisheries and tourism that depend on water quality.

“Oil-filled water that washes up on the beach filters through the porous sediment and carries the oil with it into the sand. 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.”

Kostka says, “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. These microorganisms include bacteria and also some microalgae that live in the water column and the sediments of the Gulf of Mexico.” Oil accumulations deposited on the beach surface are easily removed by, for example, scraping off the top layer of sand. However, the oil components that penetrate into the sand can only be removed by microbial degradation.

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