An Oil Spill Killed the Gulf’s Dolphins—Are Santa Barbara’s Marine Mammals Next?

A new study shows the strongest link yet between the Deepwater Horizon spill and the deaths of Gulf dolphins.

A bottlenose dolphin in the Gulf of Mexico. (Photo: Joe Raedle/Getty Images)

May 21, 2015· 2 MIN READ
Taylor Hill is an associate editor at TakePart covering environment and wildlife.

For the past five years, dolphins have been dying in the Gulf of Mexico at higher-than-normal rates.

While multiple studies have labeled the 168 million gallons of oil left behind by the Deepwater Horizon spill as a “contributing factor” to the mortalities, a new study appears to leave little doubt: The petroleum that blanketed the Gulf Coast in 2010 is killing the animals.

Researchers from the National Oceanic and Atmospheric Administration found that bottlenose dolphins stranded in the oil spill–affected area had higher rates of lung and adrenal lesions—ailments found in other marine mammals exposed to petroleum products after an oil spill—than dolphins outside the Gulf.

“These dolphins had some of the most severe lung lesions I have seen in the 13-plus years that I have examined dead dolphin tissues from throughout the U.S.,” said Kathleen Colegrove, a veterinary diagnostic laboratory professor at the University of Illinois and a coauthor of the study, which was published in the journal PLOS One.

While British Petroleum puts out press releases refuting study after study linking the disaster to animal deaths, another oil spill in Santa Barbara, California—albeit much smaller in scope—could mean petroleum-related animal impacts are coming on the West Coast too.

For Gulf dolphins, the lesions led to higher-than-average adrenal disorders and cases of bacterial pneumonia—factors that contributed to the area’s unusual mortality event, which NOAA is calling the largest-ever die-off of bottlenose dolphins in the area.

Researchers ruled out diseases that have caused dolphin deaths in the past, leading scientists to one conclusion: The BP spill contributed to the high number of dolphin deaths in Alabama, Louisiana, and Mississippi.

“No feasible alternative causes remain that can reasonably explain the timing, location, and nature of these distinct lesions,” Stephanie Venn-Watson, the lead author of the study and a veterinary epidemiologist, said on a press call Wednesday.

The Santa Barbara spill has grown from original estimates of 21,000 gallons spilled and a four-mile slick offshore to 105,000 gallons and two nine-mile slicks at sea. An onshore pipe operated by Texas-based Plains All American Pipeline burst Tuesday afternoon, flowing down a storm drain onto beaches and into the ocean.

RELATED: The New Santa Barbara Oil Spill Is a Reminder of How Little We’ve Learned

So far, only 7,700 gallons of crude have been recovered by vessels working offshore, and thousands of gallons are splattered along rocks and sandy shorelines. Early estimates suggest that as many as 100,000 gallons spilled from the pipe before the leak was stopped.

In the two days since the spill, impacts to wildlife have proved minimal: Five oiled pelicans and one sea lion were rescued and are receiving treatment at a nearby rehabilitation facility.

“Just because there’s a lot of oil in the environment doesn’t mean we will have huge numbers of animals,” Mike Ziccardi, director of the Oiled Wildlife Care Network, said in a statement. “Sometimes there are small spills with large numbers of animals and huge spills with just a few animals.”

But it’s still early, and the cleanup efforts are expected to continue for months, officials say. As the Gulf of Mexico’s dolphins show, the effects of an oil spill last long after the cleanup crews are gone.

Toni Frohoff, a cetacean researcher with the animal advocacy group In Defense of Animals, studies Santa Barbara’s resident coastal bottlenose dolphins, a population known to migrate as far north as Monterey Bay.

“Dolphins and whales feel the impacts from oil spills internally and externally—they’re exposed in a radically intense and prolonged way,” Frohoff said. “They breathe in the noxious fumes and are stuck in the water, which can cause lesions in their lungs, ulcers in stomachs, and make their adrenal glands stop functioning.”

While there is a large population of offshore bottlenose dolphins in the Pacific Ocean that will likely be unaffected by the spill, the smaller population of California’s coastal bottlenose (a separate ecotype recognized by scientists) could feel the effects.

“This is their home, and they are vulnerable,” Frohoff said.

But it’s not all doom and gloom for the dolphin. In the Gulf of Mexico, recent figures from NOAA have shown fewer dolphin strandings in each month of 2015 so far compared with last year. Last year’s strandings totaled 117, nowhere near the high of 335 in 2011—the year following the spill.

At Mississippi’s Institute for Marine Mammal Studies, Jonathan Pitchford has been studying the seasonal distributions of bottlenose dolphins along the entire Mississippi Sound for the organization.

“Early on, we saw the jump in strandings, but over the past couple years, the population studies we’re conducting have shown largely a stable population,” Pitchford said. “Not much has changed.”