Pollution from the deadly Deepwater Horizon explosion and oil spill in 2010 could take decades to biodegrade, with golf ball-sized clods of weathered crude oil staying buried on Gulf Coast beaches, according to a new paper in the journal Scientific Reports.
“This oil contains substances that are harmful to the environment and to humans,” said Florida State University oceanography professor Markus Huettel. “Understanding the fate of this buried oil is critical, as it can persist for long periods of time.”
The study published by Huettel and graduate student Ioana Bociu “found that these buried clumps of oil and sediment, usually measuring less than 10 centimetres in diameter, take roughly three decades to fully decompose,” Science Daily reports, “a result of their smaller surface area to volume ratios and the limited oxygen, moisture, and nutrients available to their live-in microbes.”
Without the “unique ecological properties of a sandy beach, the same golf ball-size agglomerates would take more than 100 years to break down.”
And along with the more common agglomerates, “more extreme contaminants discovered by the researchers would require even longer periods to completely degrade,” the news report adds. “After the Deepwater Horizon spill, we found sediment-oil-agglomerates at Pensacola Beach that were the size of an office printer, and even larger,” Huettel explained. “After burial, these would persist in the beach much longer than our golf ball-size agglomerates.”
After BP’s Deepwater Horizon oil rig exploded and caught fire, producing an environmental calamity that destroyed Gulf Coast wetlands and “flattened” biodiversity in surrounding waters, the resulting spill contaminated an estimated 965 of sandy beaches along the Gulf of Mexico coastline. “Portions of that oil were quickly removed,” Science Daily recalls, citing past research by Huettel and another colleague, and “smaller Deepwater Horizon-derived oil droplets were degraded by sand-dwelling microbes, or pervasive microscopic organisms, within just one year of washing ashore.”
Cleanup efforts also managed to capture “significant amounts of larger oil particles,” the news story notes. “But these muscular cleanup operations were not able to unearth all of the harmful oil, some of which was buried as deep as 70 centimetres in the sand.”
Huettel stressed the crucial role of tidal groundwater oscillations in aerating beach sand and nourishing microbes that gradually degrade the spilled oil. “The beach, breathing in tidal rhythm, thus can be compared to a large organism that aerobically ‘digests’ the organic matter—including oil—by inhaling oxygen and exhaling carbon dioxide,” he said.
But the process isn’t infallible, Science Daily warns.
“If the load of organic and inorganic particles grows unsustainably, once-pristine beach and coastal sands can become a muddy mess, impenetrable to oxygen, and therefore inhospitable to aerobic degraders. This ecological deterioration can result in hypoxic zones—areas deprived of oxygen—which are becoming increasingly common around the world.”
So “protecting the beaches therefore is critical to maintaining a healthy shore environment,” Huettel said.