Nearly five years after the Deepwater Horizon disaster unleashed an undersea gusher in the Gulf of Mexico, environmentalists say the spill's aftermath still threatens marine life in the region.

The National Wildlife Federation (NWF) says dolphins are still dying in abnormally high numbers off the coast of Louisiana, the recovery of an endangered sea turtle has stalled, and deep-sea corals are showing signs of damage from oil exposure. In a new, 29-page report, the wildlife advocates look at how 20 species have fared since the blowout and say many more were likely hurt.

"Given the significant quantity of oil remaining on the floor of the Gulf and the unprecedented large-scale use of dispersants during the spill, it will be years or even decades before the full impact of the Deepwater Horizon disaster is known," the NWF says. "It is clear that robust scientific monitoring of the Gulf ecosystem and its wildlife populations must continue — and that restoration of degraded ecosystems should begin as soon as possible."

The group compiled findings from numerous researchers studying the aftermath of the blowout, which killed 11 workers on the drill rig Deepwater Horizon and left crude oil spewing into the Gulf for three months. Oil major BP, which owned the well at the heart of the disaster, has paid more than $32 billion in cleanup costs, compensation, and fines and faces nearly $14 billion more in a court case now pending in New Orleans.

The Kemp's ridley sea turtle, which nests along Gulf Coast beaches, had been an example of successful recovery efforts for endangered species before the disaster, NWF spokeswoman Lacey McCormick told VICE News.

Since conservation efforts began in earnest in the 1980s, "the upward trajectory of the species was amazing," McCormick said. But as many as 65,000 of the animals may have died in 2010, and the number of nests — which had been growing by 15 to 20 percent a year before the disaster — dropped 25 percent in the next two years, she said.

"It's sort of becoming clear that the recovery of the Kemp's ridley sea turtle, which we once considered basically pretty much inevitable, now appears to be in doubt," McCormick said.

An endangered Kemp's ridley sea turtle. (Photo via Flickr)

And scientists are still tracking what they call an "unusual mortality event" among dolphins in the Gulf — a spike in fatalities that began two months before the spill, but has persisted ever since. More than 1,100 dolphin deaths have been logged since the spill was capped in July 2010, the National Oceanic and Atmospheric Administration (NOAA) says.

While NOAA is looking into whether disease played a role in the deaths, the numbers aren't running high along the Texas and Florida coasts, which saw little oil.

**Related: **Scientists say an area the size of Rhode Island is coated with oil from the BP well explosion

BP issued its own 5-year report in mid-March that found no "significant long-term impact" to any Gulf species. BP public-relations chief Geoff Morrell called the NWF report "a work of political advocacy" that "conveniently overlooks" government and independent studies of the spill's legacy.

"The dire predictions made in 2010 have fortunately not come to pass — in large part because of the Gulf's resilience, natural processes, and the effectiveness of response and clean-up efforts mounted by BP under the direction of the federal government," Morrell said in a written statement.

But McCormick told VICE News that much of the federal research documenting the damage remains under wraps as the court cases go on.

"It would be great to have that right now," she told VICE News.

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