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Valdez 'bugs' chomp away.

Valdez 'bugs' chomp away

Last month, Environmental Protection Agency biologists initiated experiments on a soiled beach in Alaska's Prince William Sound to see whether treating its sandy and rocky shoreline with either of two types of fertilizer would enhance the natural detoxification of crude-oil residues (SN: 6/17/89, p.383). Preliminary data from those tests, released late last week, indicate that fertilizing indigenous aquatic bacteria indeed appears to accelerate the breakdown of oil spilled from the Exxon Valdez supertanker.

According to the EPA report, "natural biodegradation of the oil was already well underway ... by the time the fertilizer was applied." This, it says, explains why the researchers found so many oil-degrading microbes at the start of their study. Just one week after beach fertilization began, however, the microbial communities had expanded measurably. And, as suspected, the fertilizers' formulations appeared to influence their efficacy. Sites treated with the water-soluble fertilizer contained 30 times more oil-degrading bacteria than did untreated beach plots. Sites sprayed with a fertilizer incorporating a vegetable oil to help it bind to the crude oil, however, housed 100 times more of the beneficial bacteria than nearby untreated zones.

Observation of the oil/fertilizer-treatment areas "clearly shows a striking disappearance of the [tanker] oil from rock surfaces," the report says. While EPA scientists haven't established that the bacteria ate the oil rather than simply loosening it to be washed back into the sound, such analyses are underway. Early data do indicate that the fertilizers have not collected in near-shore waters or overfed offshore algae, contributing to an oxygen-depleting algal bloom.

Noting the preliminary success of these bacterial-feeding regimes, EPA has expanded its Valdez microbial-detoxification program to include studies of nutrient movement within the beach and to monitor for adverse effects of the nutrient releases.
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Title Annotation:Exxon Valdez supertanker
Publication:Science News
Date:Jul 15, 1989
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