As we mark the fifth anniversary of the explosion that rocked the Deepwater Horizon rig, claiming 11 lives and sparking a 87 day-long, 200-million-gallon oil spill in the Gulf of Mexico, studies continue to reveal the devastating impact of the oil—and dispersants used in clean up—on marine life. Recent reports show that the dispersants were more damaging to corals than the oil itself, and continue to diminish shellfish and sea turtle populations, while large questions loom over the ongoing unexplained deaths of dolphins along the Gulf Coast. And, as the NRDC points out, it will take years, if not decades longer to fully understand the effects of the disaster.

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The oil that leaked from the Macondo well head affected over 1,000 miles of the coastline of Louisiana, Mississippi, Alabama and Florida, with BP confirming just last month that they were working to clean up a 25,000 pound tar mat at East Grand Terre Island, La.

In addition to the ongoing clean up of oil, new research is confirming concerns about the effects of the dispersant that was used in the immediate aftermath of the spill. In applying the dispersant underwater—as opposed to on the surface—BP conducted what Erik Cordes, associate professor of biology at Temple refers to as a “grand experiment in real-time.” These chemical dispersants do not “clean up” the oil, but rather mix with it and accelerate the dispersal process, but the combination of oil and dispersant has now been shown in research by Temple University to be more harmful to corals than the oil itself.

Related: There are still 2 million barrels of BP’s Deepwater Horizon oil hanging out in the Gulf of Mexico

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Moreover, researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute note that “Although the use of dispersants decreased the impact of oil to shorelines and surface-dwelling organisms, such as birds, dispersants allowed the oil to be more easily taken up by organisms that live in the water column. Rather than disappearing, the dispersed oil ended up in bottom sediments, where it remains, posing future threats to [marine] organisms,” which is to say we may see damaging releases of oil from the seafloor for years to come.

As it stands, several marine animal populations are yet to return to their pre-Deepwater Horizon levels. A comprehensive report from the National Wildlife Federation notes an ongoing decline in the number of ridley sea turtle nests and lower spawning rates of speckled trout. In addition, there are signs of “abnormal development in many species of fish, including mahi mahi, Gulf killifish and bluefin and yellowfin tuna,” and strong evidence to show that “12 percent of the brown pelicans and 32 percent of the laughing gulls in the northern Gulf died as a result of the oil spill.”

deepwater horizon graveyard art piece

Moverover, the NWF notes, “Dolphins on the Louisiana coast were found dead at four times historic rates in 2014, and there is increasing evidence that these ongoing deaths are connected to the oil spill.” Speaking to NPR, Cynthia Sartou, executive director of the Gulf Restoration Network said, “nobody really is able to say what we may find in five years, 10 years. It’s really distressing to me. It’s not publicly seen but it is out there. It’s in the marine environment, and so whether we see it or not the potential impacts of its presence may plague us for decades.”

+ BP Deepwater Horizon

Images via U.S. Coast Guard, Green Fire Productions via Flickr Creative Commons, U.S. Fish and Wildlife, and Shutterstock.