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 additional unseen effects can continue on undetected for years.
Swimming through oil slicks made dolphins' lives difficult enough. But those exposed to the oil in the region were also found to be extremely ill, and strandings of both dolphins and sea turtles increased significantly in the years following the spill. It will still be a few years before we know if their populations in the Gulf have been affected.
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. But the effects of the oil are also being passed onto birds that are not directly exposed to oil. Scientists have found that pelicans nesting in Minnesota, which feed in the Gulf of Mexico during winter, are laying eggs that contain chemical compounds from petroleum and dispersant. There is concern that the presence of these chemicals will lead to developmental and reproductive problems.
The oil may have wiped out microscopic populations of plankton and microbes—including the larvae of fish and other animals that people eat—almost immediately. At its worst, this could mean that whole groups of young born in the same year may have been killed, which could create gaps in species populations and impact the entire food web. For example, the mouth of the Mississippi is an important spawning area for bluefin tuna; they were spawning during the time of the spill. It will be a few years until scientists know for sure how their population was affected, but it's possible that up to 20 percent of the western population of endangered Atlantic bluefin tuna larvae may have been killed by the BP oil spill.
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 baby coral exposed to oil and dispersant had lower survival rates and difficulty settling on a hard surface to grow.
There were some reports of deformed wildlife after the spill. For years following the spill there were reports of fish with lesions and deformities. These were likely caused by stress as the animals tried to avoid pollution in the water. And there were 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.