Dispersants used to fight BP oil spill damaged marine food chain, study finds
Alabama researchers studying the impact oil dispersants used to break up oil from BP’s 2010 Deepwater Horizon spill have found that the chemicals and the way in which they were used may have devastated the food chain in certain parts of the Gulf of Mexico.
The study, published Tuesday in the scientific journal PLoS ONE and praised by peers for its scope and accuracy, simulated the effects of pollutants on phytoplankton and ciliates by pumping water from Mobile Bay into large drums. Researchers then added oil, chemical dispersants, and a combination of both oil and dispersants to the water samples in proportions found in the Gulf during the BP oil spill. They then studied the effects these contaminants had on the microscopic marine life.
After a few days, researchers found that the plankton count in barrels containing oil alone grew, reinforcing an earlier Alabama study that found plankton quickly devoured carbon-rich oil from the BP spill. However, the number of plankton was severely diminished in samples containing dispersants and oil treated with dispersants.
“In those tanks, all of the energy seems to get trapped in the bacterial side. There were lots of bacteria left but no bigger things. It’s like the middle part of the food web is taken away,” lead researcher Alice Ortmann of the University of South Alabama and Dauphin Island Sea Lab told the Associated Press. Dr. Ortmann added that she and her fellow researchers, including some from Auburn University, were surprised at how devastating the dispersant alone was to the plankton.
Plant-like phytoplankton and ciliates, which propel themselves with hairlike cilia, form the foundation of the food chain. Both are consumed by larger zooplankton, which are eaten by small crustaceans, which are eaten by small fish and so on.
Brian Crother, a biology professor at Southeastern Louisiana University, told the Associated Press that the new study clearly shows that the dispersant, not oil, was to blame for the loss of plankton in the Gulf. “If these guys are on the money, they have pointed to something really disastrous happening in the Gulf,” Dr. Crother told the Associated Press.
After BP’s Deepwater Horizon rig exploded off the Louisiana coast, the Macondo well gushed oil for more than 12 weeks. Amid repeated failed attempts to stop the oil, BP workers resorted to treating the growing spill with Corexit oil dispersant. More than a million gallons of Corexit were dumped onto the spill from airplanes and boats. An additional 800,000 gallons were pumped into the oil geyser near its source in an attempt to break the oil into tiny particles – an unprecedented application using an unprecedented volume of chemical dispersants. Shortly afterward, scientists documented giant plumes of dispersed oil twisting through miles of the Gulf from the sea floor to the surface.
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