Birds, fish, dolphins and turtles are still struggling in the Gulf of Mexico, four years after the worst oil spill in US history, a leading wildlife group said Tuesday.

The 2010 BP spill spewed 4.9 million barrels of oil into the waters off Louisiana, also sullying the coastlines of Mississippi, Alabama, Texas and Florida.

"The science is telling us that the impacts of this are far from over," said Doug Inkley, senior scientist at the National Wildlife Federation.

"Based on other oil spills, the impacts are likely to last for years, if not decades."

A report issued by the National Wildlife Federation summarized recent scientific studies on 14 different types of creatures affected by the spill.

Researchers have found evidence that dolphins in Louisiana's heavily oiled Barataria Bay suffer from abnormal hormone levels, lung disease and anemia.

Overall, dolphins have been stranding at three times the historic rate, with some 900 washing up dead or dying from 2010 until 2013, the report said.

About 500 dead sea turtles have been found annually in the area, also a rate much higher than that seen in years prior to the disaster.

Bluefin and yellowfin tuna have been shown to suffer irregular heartbeats due to a chemical in oil from the spill, which began after the Deepwater Horizon drilling rig exploded and sank, killing 11 people.

Toxic oil compounds have been found at increasing levels in the blood samples of loons that winter along the Louisiana coast, it added.

Sperm whales that were closer to the well have higher levels of DNA damaging metals than those in other parts of the world.

Oil is still being removed from the coast, too, said Sara Gonzalez-Rothi, the National Wildlife Federation's senior policy specialist for Gulf and coastal restoration.

"Last year, nearly five million pounds of oiled material from the disaster were removed from Louisiana's coast," she said.

"And that's just what we've seen. An unknown amount of oil remains deep in the Gulf."

Earlier this month, the US Environmental Protection Agency ended its ban on BP obtaining government contracts following the disaster.

The five-year deal with the EPA will allow the British company to pursue new oil exploration leases in deepwater tracts in the Gulf of Mexico.

In pleading guilty to the spill, BP agreed to pay the government $4.5 billion to settle criminal charges in the case.

It also agreed in 2012 to settle damage claims by businesses and individuals for about $7.8 billion.

Four years after the Deepwater Horizon oil spill, wildlife still struggling
Washington (UPI) Apr 8, 2013 - Roughly four years after BP's Deepwater Horizon oil rig exploded, spilling 200 million gallons of oil -- the biggest oil spill in U.S. history -- wildlife in the Gulf of Mexico continue to struggle.

According to a new report by the National Wildlife Federation, bottlenose dolphins, sea turtles and other animals continue to die at heightened rates, and many Gulf Coast ecosystems remain slow to recover.

"Four years later, wildlife in the Gulf are still feeling the impacts of the spill," Doug Inkley, senior scientist at NWF, said in a recent press release. "Bottlenose dolphins in oiled areas are still sick and dying and the evidence is stronger than ever that these deaths are connected to the Deepwater Horizon. The science is telling us that this is not over."

The Deepwater Horizon erupted in flames on April 20, 2010, killing 11 men working on the rig and spilling millions of gallons of oil into the Gulf. Although the tourism industry has mostly bounced back, and beaches are clean, fisherman report that catches remain lower than average -- neither the shrimp nor oyster industries are back to full strength.

Now, NWF's new report suggests non-commercial marine animals are faring even worse.

Worst among the study's findings are the continuing effects of the oil spill on dolphins and turtles. Some 500 sea turtles have been found dead every year for the past three years in the affected regions. Last years, dolphins died at three times the normal rate, and scientists have found oil to be affecting dolphins lung capacity, making them sick.

Sperm whales have been found with unusually high levels of DNA-damaging metals -- metals that match the components of the oil spilled by BP.

"Despite what BP would have you believe, the impacts of the disaster are ongoing," said Sara Gonzalez-Rothi, NWF senior policy specialist. "Last year, nearly five million pounds of oiled material from the disaster were removed from Louisiana's coast. And that's just what we've seen. An unknown amount of oil remains deep in the Gulf."