The oil dispersant that was used to clean up the oil after the Deepwater Horizon oil spill had likely toxic effects for oysters, according to Morris Animal Foundation-funded researchers at the University of Connecticut. The team determined this by comparing the low levels of toxicity of oil, the dispersant and a mixture of the two on Eastern oysters.
There’s an unfortunate trade-off to using dispersants like this. They may prevent giant oil spills from washing ashore and damaging wetlands, but they also cause negative effects for species below the ocean’s surface that might have been spared if dispersants weren’t used,
…said Lindsay Jasperse, a member of the university’s research team that published the study in the journal Aquatic Toxicology.
After the Deepwater Horizon oil rig spilled more than 170 million gallons of oil into the Gulf of Mexico, nearly two million gallons of Corexit 9500 was deployed into the water area to break the oil down.
Oysters serve as water purifiers, filtering out particles and nutrients from the water to improve the quality for surrounding species. Oyster reefs also prevent erosion and provide habitat and protection for many crabs and fish. Unfortunately, as they are immobile and so abundant, they are at a significant risk for critical exposure to oil and oil dispersants following environmental disasters.
In a controlled environment, researchers compared the toxicity of oil alone, the dispersant alone and a mixture of the two on oysters.
They namely tested both the oysters’ feeding rates, or how well they could filter algae, and immune functions, or how well they could absorb and destroy bacteria, which indicates an oyster’s ability to fight off infection. Findings included:
- For the oysters’ immune function, the dispersant alone was the most toxic, followed by the dispersant and oil mixture. Oil alone did not impact the oysters’ immune function at all.
- For the oysters’ feeding rates, they found the mixture of the dispersant and oil had the most toxic effect, followed by oil alone and then the dispersant alone.
Knowing the effects dispersants and oil have on oysters can help us make better mitigation recommendations the next time an environmental and ecological crisis like this happens. Species are interconnected, and what harms oysters will likely cascade through their ecosystem to the detriment of all,
…said Dr. Kelly Diehl, Morris Animal Foundation Interim Vice President of Scientific Programs.
