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June 15, 2020

10 years later, whales and dolphins are still recovering from Deepwater Horizon disaster

Ten years ago today, a research ship studying devastation from BP’s Deepwater Horizon found a dead  25-foot-long endangered sperm whale. Oil had been gushing into the Gulf of Mexico for almost two months, without an end in sight. And as a result, the disaster killed almost 100 endangered sperm whales in the Gulf out of a population of only about 1,600 in 2010.

At least 150 dolphins and whales were found dead during the Deepwater Horizon disaster response. But not all marine mammals killed by this drilling disaster were found and counted, in part because of the vast size of the Gulf and because many sank or were consumed before they could be spotted. For each dead whale counted there could be 50 more that die undetected.

Oil from the Deepwater Horizon contaminated prime habitat for dolphins and whales in the northern Gulf of Mexico. Oil exposure caused lung disease, suppressed immune systems and failed pregnancies. Animals that died from these injuries were part of the largest and longest marine mammal unusual mortality event (UME) on record in the northern Gulf. An UME is an official designation of an unexpected and significant die-off of a group of marine mammals. An UME demands immediate response to look for the cause of the deaths and how to help.

Marine mammals and the Deepwater Horizon disaster:

  • More than 1,400 marine mammals were seen in the oil slick.
  • All 21 species of marine mammals found in the Gulf were exposed to oil.
  • In hard hit Barataria Bay, Louisiana, bottlenose dolphins suffered 46% more failed pregnancies and an estimated 800 dolphins died.
  • 17% of the Gulf of Mexico Bryde’s whales died. Nearly half were harmed by oil. With only approximately 40 whales alive today, they are among the most endangered whales in the world. The oil industry continues to push them to the brink of extinction.

The diversity of marine mammals affected by the Deepwater Horizon and the scale of the impact was unprecedented. Dolphins and whales play an important role in the food web as top predators.  These animals have long life spans and reproduce slowly-some groups will take decades to recover. Our oceans are counting on us to prevent this from happening again and protect new areas from this dangerous industry.  

This is the fourth piece in an Oceana series looking back at the repercussions of 2010 BP Deepwater Horizon disaster and highlighting notable moments in the 87 days that followed, as millions of gallons of oil spewed into the Gulf of Mexico. To learn more about the BP disaster, explore Oceana’s report, Hindsight 2020: Lessons We Cannot Ignore from the BP Disaster.

Explore other key moments in the series: Read about current efforts to stop the expansion of offshore drilling, BP’s failed attempts to stop gushing oil with junk and what happened when oil reached Florida’s beaches.