This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In a deep, dark part of the Gulf of Mexico, the number of marine animals plummeted by about 60% in the years following the 2010 Deepwater Horizon explosion, a new study found. In a crucial part of the Gulf between the light surface and the darkest depths, where the BP-operated well failed and dumped 134 million gallons of oil (507 million liters), the number of fish found dropped by 63.5% from the year after the spill to 2015.
Crustaceans, including shrimp and krill, a key food for whales, went down 62%, and larger animals like squid and octopuses fell 59.7%, according to a study published Monday in the journal PNAS. And those populations haven't come close to recovering, the study found. Researchers focused on the ocean's "twilight zone," a vast area above the seafloor, where much of the surface marine life, including dolphins and whales, feasts on creatures.
Yet little is known about this gigantic ecosystem, and this region of the Gulf had not been studied before the 2010 spill, said study lead author Tracey Sutton, a biological oceanographer at Nova Southeastern University. A 2011 post-spill exploration cited in the research, which used six sets of nets at different depths and acoustic sonar, gave scientists a good sense of how much sea life was in the area between the surface and 5,000 feet deep (1,500 meters). They returned to the same place with the same equipment three and a half years later and found sea life was between one-third and one-quarter of what it was in 2011.
"We saw this big decline," Sutton said. "The question was then why? So we looked at all of the natural variables we thought could account for it, namely temperature, oxygen supply and food.
None of those vary with the decline. The event that did was the oil spill. So we think that's the most likely cause of the decline." Researchers have kept sampling since 2015, and the low populations remained, with a slight rise in 2022 and 2023 that did not prove statistically significant or lasting, Sutton said.
Sutton's team documented the population declines with three different lines of evidence: what they caught in the nets, what their acoustic sonar found and genetic studies showing the species losing genetic diversity because of inbreeding. A lot of marine life died instantly after the explosion, which killed 11 workers, and from nearly five months of leaking oil and gas. Those pollutants got stored in the eggs of survivors and subsequent generations of critters got more compromised and weaker, Sutton said.
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