Researchers analyzing the impacts of the 2010 Deepwater Horizon oil spill reveal that the damage wasn’t restricted to the northern Gulf of Mexico. Unlike the oil, mobile marine animals present during the multi-month spill, including more than 320,000 sea turtles, have traveled throughout the Atlantic Ocean. The findings were published in Biology Letters last week.
Most assessments of the Deepwater Horizon disaster have overlooked the impacts to oceanic-stage wildlife that migrate or disperse between the gulf and distant countries. That’s partly because it’s hard to determine exactly when and how many animals were passing through.
So, University of Miami’s Nathan Putman and colleagues used an ocean-circulation computer model to estimate the movements of young turtles between nesting beaches and the site of the oil spill. The turtle species that were most abundant in the area are green (Chelonia mydas), loggerhead (Caretta caretta), and Kemp's ridley (Lepidochelys kempii) sea turtles. The latter two are endangered.
Their simulations used virtual particles to represent the turtles, and a thousand of these particles were “released” daily between simulated April through August 2010 conditions. The particles were also backtracked for five years to determine where they came from before reaching their final position at the spill site.
The team estimate that 175,064 green, 21,363 loggerhead, and 3,693 Kemp's ridley turtles were in the vicinity of the affected area during the spill, and they had come from populations throughout the Gulf of Mexico, the Caribbean, and the Atlantic Ocean. Most of them came from Mexico, and the rest came from Costa Rica, countries in northern South America, the U.S., and west African countries, in descending order. That means more than 95 percent of the turtles were from nesting populations outside of the U.S.
"There is a perception that the spills impacts were largely contained to the northern Gulf of Mexico, because that is where the oil remained," Putman said in a statement. "However, this overlooks the movement of migratory and dispersive marine animals into the area from distant locations."
This map shows the likelihood of virtual particles arriving to the Deepwater Horizon oil spill site (yellow star) from major sea turtle nesting sites (white squares) within five years. Colors indicate particle density, and locations with warmer colors had a relatively high probability of transport into the spill site. Nathan Putnam/UM Rosenstiel School of Marine and Atmospheric Science