A federal study of sea otters in Prince William Sound, Alaska, where the Exxon Valdez supertanker spilled around 30,000,000 gallons of oil about 25 years ago (the second largest spill after the Deepwater Horizon disaster) has concluded that the otters have returned to pre-spill numbers. And it just took a quarter century...
One of the reasons why it took so long, according to the study, is that sea otters feed on clams and oil from the spill remained in sediment at the bottom of the water for years after the spill. "One of the lessons we can take from this is that the chronic effects of oil in the environment can persist for decades," lead author and research biologist Brenda Ballachey told the CBC.
Sea otters rely on their thick fur to survive in cold water. Fur covered by oil loses its insulating value. A sea otter with oiled fur must groom itself, which leads to the ingestion of oil and causes other problems, including time taken away for feeding, Ballachey said.
At the time of the Exxon Valdez spill, emergency responders recovered nearly 1,000 sea otter carcasses from the entire spill area, with estimates for the total number of immediate otter deaths going up to around 3,000.
Even a decade after the spill sea otters weren't returning to the areas hit the hardest by the disaster. According to the study, things started to get better after 2007, and it's only in 2009 that many areas of western Prince William Sound were back to sea otter population of levels that compared to pre-spill population.