On Deepwater Horizon Anniversary, Dolphins Face Decades of Recovery

New research shows that a wide range of marine life is suffering long-term harm six years after the biggest oil spill in U.S. history.
Bottlenose dolphins are riding the wake of a ship. (Photo: Getty Images)
Apr 20, 2016· 3 MIN READ
Katy Reckdahl is a New Orleans–based writer. Her work has appeared in The New Orleans Advocate, The New York Times, and The Atlantic, and other news organizations.

Six years ago today, on April 20, 2010, the Deepwater Horizon oil rig exploded in the Gulf of Mexico, killing 11 workers and spewing 205 million gallons of crude oil for 87 days, devastating wildlife and coastal communities.

Now scientists putting together a federal environmental-restoration plan are estimating that it will likely take 40 to 50 years for the hardest-hit populations of common bottlenose dolphins to recover from the disaster on their own. Kathleen Colegrove, a veterinarian pathologist on a team of nearly 20 researchers examining dolphin deaths in the oil-spill zone as part of a new study, said that recovery may seem long, but because of the effects she has seen in adult dolphin females and stillborn or newborn dolphins, she thinks that the estimates are accurate. “Reproductive effects have long-standing consequences,” Colegrove said.

Six years after the disaster, researchers are finding long-term damage in a broad group of marine creatures.

In a research summary, the National Oceanic and Atmospheric Administration didn’t pull any punches. “Current evidence suggests that the Deepwater Horizon oil spill is a contributor to the largest and longest-lasting die-off in the Gulf of Mexico,” scientists wrote. They summarized the body of work about dolphins as “a picture of chronic poor health, failed pregnancies, and increased mortality of coastal bottlenose dolphins in the aftermath and footprint of the Deepwater Horizon oil spill.”

A government document called the Programmatic Damage Assessment and Restoration Plan carefully outlines the injuries that the spill caused as it released an average of more than 1.5 million gallons of oil into the Gulf every day, creating a detectable oil slick the size of Virginia that was visible along the coastline and in the water long after the well was capped.

Earlier in April, U.S. District Judge Carl Barbier approved an $8.8 billion settlement with oil giant BP, the party that he ruled was primarily responsible for the spill. The U.S. Department of the Interior will use that money to implement the restoration plan.

Colegrove’s work builds on a large body of research showing how the enormous spill affected dolphins. To date, the data show that Louisiana’s estuary dolphins, which live closest to the shore, were killed by the oil at high rates and are struggling to carry their babies to term.

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The oil devastated the pods of bottlenose dolphins that live in Barataria Bay, just off the southeastern coast of Louisiana, which died at a 35 percent higher rate and saw nearly a 50 percent drop in reproductive success, according to research published last year. Those numbers won’t rebound anytime soon because dolphins are slow to mature and have 380-day pregnancies.

People may grieve dolphin mortalities more than those of other creatures. “I think people feel a kinship with dolphins because of their intelligence and their charismatic personalities,” Colegrove said. But the overall findings—that the oil spill depleted key populations—are echoed in hundreds of other species, even the horsefly that two Louisiana State University Agricultural Center researchers have been studying.

Claudia Husseneder and Lane Foil have found that in oiled wetlands, the population of the greenhead horsefly crashed, and few of its larvae grew. “While nobody cares much about this bloodsucking nemesis, this species is a bioindicator of the food web in marshes,” Husseneder said.

The damage assessment’s list of injuries is long: flawed gills and livers in the southern flounder; adverse effects at all oyster life stages; DNA damage in freshwater turtles; anemia, liver dysfunction, and alterations in heart function in birds; and growth and reproductive issues in fish, such as the juvenile red drum, Pacific white shrimp, and Gulf killifish.

Not all the Gulf’s 22 species of marine mammals are as easy to find as its bottlenose dolphins. The others were tracked through audio recorders and catalogs of visual sightings. Researchers have determined that the endangered sperm whale, though it lives farther from shore, lost 7 percent of its population and will take an estimated 21 years to recover. Bryde’s whales, a large, filter-feeding baleen, lost 22 percent of its population and will take 69 years to recover, the plan estimates.

BP has consistently denied any culpability for animal die-offs. In the case of dolphins, BP spokesperson Geoff Morrell has said that nothing definitively links sickness and death in the Gulf’s dolphins to exposure from the well.

Sometimes it is tough to refute Morrell’s statements, because while the massive amounts of data collected by researchers have long been available online, some researchers who worked on the damage assessment have been barred from speaking with reporters about their research until the long-running litigation over the spill concludes.

Demetri Spyropoulos, Alexis Temkin, and other scientists from the Medical University of South Carolina are using stem cells from sentinel animals—dolphins, whales, American alligators, and humans—to test reactions to dioctyl sodium sulfosuccinate, or DOSS, an ingredient in Corexit, a dispersant used to clean up the spill. The South Carolina team has identified the compound as a likely “obesogen,” an endocrine disruptor that has the potential to alter a fetus’ stem cells, making them more likely to become fat cells. “What doesn’t kill you makes you fatter,” team members sometimes quip.

Such effects could be generational in oil-exposed people, leading to more newborns that are predisposed to obesity, they said.

Colegrove’s team is also looking at the long-term effects of dolphin fetuses exposed to oil and of adult dolphins chronically sickened by oil—most often through damage to lung and adrenal glands—to the point where the mammals struggle to reproduce. Her team found that 22 percent of dolphins from the oil-spill zone had bacterial pneumonia, compared with 2 percent outside the zone. While 15 percent of stillborn and juvenile dolphins found outside the spill zone had abnormal lungs, 88 percent in the zone had such abnormalities, including partially or completely collapsed lungs.

“We found fetal distress and infections in wombs that led to failures,” said Colegrove, who added that she encountered some of the worst lung lesions she’d ever seen, “and that was consistent with what we’d seen in previous studies. It’s the downstream effects of having a sick mom.”