There were some immediate impacts to the animals of the Gulf of Mexico that could be seen with the naked eye: pelicans black with oil, fish belly-up in brown sludge, smothered turtles washed up on beaches. But not much time has passed since the spill, and it will take many more years of monitoring and research to understand what happened.
Strandings of both dolphins and sea turtles increased significantly in the years following the spill. "From 2002 to 2009, the Gulf averaged 63 dolphin deaths a year. That rose to 125 in the seven months after the spill in 2010 and 335 in all of 2011, averaging more than 200 a year since April 2010," reported Reuters in 2015. Since then, dolphin deaths have declined, and long-term impacts on the population are not yet known. Kemp's ridley sea turtle nests have gone down in the years since the spill, and long-term effects are not yet known.
Seabirds were initially harmed by crude surface oil—even a small bit of oil on their feathers impeded their ability to fly, swim and find food by diving. Seabird losses may have numbered in the hundreds of thousands, but reliable estimates are hard to come by. Looking beyond the sea, researchers are currently studying how oil may have affected land birds that live in the marshes along the Gulf coast.
Invertebrates in the Gulf were hard hit by the Deepwater Horizon spill—both in coastal areas and in the deep. Shrimp fisheries were closed for much of the year following the spill, but these commercially-important species now seem to have recovered. Deep-water corals grow very slowly and can live for many centuries. Found as deep as 4,000 feet below the surface, corals near the blowout showed signs of tissue damage and were covered by an unknown brown substance, later identified as oil from the spill. Laboratory studies conducted with coral species showed that coral larva exposed to oil and dispersant had lower survival rates and difficulty settling on a hard surface to grow.
The impact of the spill on fish communities is still largely unknown. Lab studies have shown that oil can cause heart defects in the developing larvae of bluefin tuna and other fish, but we won't know if this occurred in the wild until after those larvae would have grown up. Some fish larvae populations actually grew after the spill, as they had more food in the form of oil-eating microbes.
There were some reports of deformed wildlife after the spill. For years following the spill there were reports of fish with lesions and deformities, and some reports of eyeless and deformed shrimp after the spill. However, consuming Gulf seafood is now completely safe.
Over 1,000 miles of shoreline on the Gulf of Mexico, from Texas to Florida, was impacted by oil from the Deepwater Horizon blowout. Much of this area has been cleaned, but eroded shorelines are taking longer to recover and erosion rates have accelerated in these areas.
You can explore more ecosystem effects in our interactive.