Crude oil from the Deepwater Horizon spill in 2010 caused severe defects in the developing embryos of tuna and other large marine species, scientists have discovered.
The study by a team of NOAA and academic scientists is published in the Proceedings of the National Academy of Sciences. It shows how the disaster may have affected Bluefin and Yellowfin tuna, along with other large predatory fish that spawn in offshore habitats in the northern Gulf of Mexico during the spring and summer — the time of the Deepwater Horizon oil spill, which saw millions of gallons of crude oil pouring into the Gulf.
The team assessed the impacts of field-collected Deepwater Horizon (MC252) oil samples on embryos of three pelagic fish: two species of tuna and an amberjack species. It found that exposure to crude oil adversely affects heart development by slowing the heartbeat or causing an uncoordinated rhythm — particularly bad for large predators like tuna, which rely on moving swiftly to catch their food — and which can ultimately lead to heart failure.
The newly-hatched fish were chosen for research, as they were believed to be the most affected by the oil spill. These species produce buoyant embryos that float near the ocean surface, potentially in harm’s way as crude oil from the damaged wellhead rose from the seafloor to form large surface slicks.
"The timing and location of the spill raised immediate concerns for Bluefin tuna,” said Barbara Block, Ph.D., a study co-author and professor of biology at Stanford University. "This spill occurred in prime Bluefin spawning habitats, and the new evidence indicates a compromising effect of oil on the physiology and morphology of bluefin embryos and larvae."
Scientists say the concern is that the immediate death of eggs and larvae and the longer-term heart deformities will reduce the number of fish in a species already in trouble. Bluefin tuna take between eight and 14 years to reach maturity, which could make it difficult to determine the long-term effects of the exposure to the oil.
The authors suggest there may also have been cardiac-related impacts on swordfish, marlin, mackerel, and other Gulf species.
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