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HABITATS AND SPECIES AFFECTED

Federal wildlife officials reported that 1,144 sea turtles, 609 of which were dead, and 109 marine mammals (mostly dolphins, almost all of which had already died) were collected on or near the shore. Many of these animals were visibly oiled, but some may have died of other causes. In the case of sea turtles, scientists believe that many of the deaths may be attributable to drowning in shrimp trawls in the mad dash that occurred in anticipation of fisheries closures due to the spill. Whatever the cause, the turtles have been rendered more vulnerable to the oil spill effects.  Wildlife rescuers collected more than 8,000 birds; tragically, about 6,000 of these birds had already died when they were collected. Others were rehabilitated but may not have ultimately survived the traumatic experience. Many more birds were oiled by the crude polluting coastal marshes.

Numerous species of fish, seabirds, marine mammals and sea turtles have been impacted from the oil spill. Collecting the stranded animals reveals only a portion of the oil spill’s casualties. It may be decades until the true consequences of the oil spill on wildlife are understood.  During the oil spill, about one-third of the Gulf of Mexico’s waters were closed to fishing. Some fisheries are still closed, and  concerns remain about food safety.

OPEN-WATER HABITAT

At the height of the oil spill, Atlantic bluefin tuna, a critically imperiled species whose numbers have already been decimated by overfishing, were spawning in the Gulf of Mexico. This area — particularly the area affected by the spill — comprises the only known spawning grounds for the western population of Atlantic bluefin tuna. The oil proved toxic to eggs, which float near the surface, and to young fish hiding in floating sargassum seaweed, which may have collected oil and increased the fish’s exposure. On May 24, 2010, the Center petitioned the federal government to protect Atlantic bluefin tuna under the Endangered Species Act, pointing out that the few adult tuna that made it past the gauntlet of longlines back to their Gulf spawning grounds were then threatened by oil and toxic dispersants. Scientists estimate that the oil spill killed more than 20 percent of juvenile western Atlantic bluefin tuna in 2010 — and that estimate doesn’t consider the expected long-term negative effects of the oil spill in the tuna’s breeding habitat.

Endangered sperm whales were spotted passing through the giant slick. Blue, fin and sei whales also swim through these waters. As air-breathing mammals, whales traveling through the area had no choice but to surface amid the oily sheen for breath. Breathing toxic fumes can damage mucous membranes and airways. In extreme cases, it can even cause death. In addition, experts predicted that the plankton that baleen whales like blue whales and fin whales rely on would suffer major declines from the pollution.

Another species at the base of the food chain, the menhaden, may also feel the impacts of the spill. In addition to supporting a fishery harvesting on average more than one billion pounds a year, the menhaden is a critical food source for sharks, tuna, swordfish and marine mammals. It’s a particular favorite of fish-eating birds like herons, gannets, gulls, osprey and brown pelicans. As with many other species, the oil spill struck during the middle of the menhaden’s spawning season.

NEAR-SHORE AREAS

The sea-grass beds south of the Chandeleur Islands and elsewhere along the coast provide food, shelter and nursery sites for a multitude of marine life, including numerous fish and shark species. Sea-grass beds also provide key habitat for West Indian manatees that munch on the sea grass and raise their young in these shallow, calm waters. Oil can smother sea grass, robbing these gentle giants of their food source. In addition, oil can get into manatees’ eyes and sensory hairs on their noses when they surface to breathe, causing inflammation and infection that impair the animals’ ability to breed and feed.

Kemp’s ridley sea turtles forage and nest along the Louisiana coast. Breton Sound and the Chandeleur Islands, the first coastal areas to be hit with BP’s oil, are particularly important areas for this species. Ironically, the turtle’s success in crawling toward recovery may have put it at risk due to increased numbers of juveniles coming to nearshore waters during the spill to forage on blue crabs, many of which were contaminated by toxic oil. Adult females also passed through the area on their way to nesting beaches along the coasts of Texas and Mexico during the height of the spill.

Oil can affect sea turtles in a number of ways. Ingestion of oil through contaminated food and absorption through direct physical contact can lead to damage to the turtle’s digestive tract and other organs. Oil can also cause inflammation of mucous membranes in the eyes, nose, and throat, which can lead to infection. Eggs laid in oil-contaminated sand — or by an oil-contaminated mother — may not develop properly, while newly hatched turtles may become oiled while crossing a contaminated beach. Hopes remain that efforts to relocate sea turtle eggs were successful, and that the turtles will survive their migrations and return to nest one day.

Another species whose success story may have been turned on its head is the brown pelican. Delisted in 2009, the brown pelican was one of the more prominent victims of oiling, loss of habitat and loss of food supply.

COASTAL WETLANDS AND BEACHES

Oil coating coastal marshes and other wetlands contaminated sediments, poisoned wildlife and smothered salt-marsh grasses and other wetland vegetation. The death of vegetation in wetlands could result in significant erosion and habitat loss. Sandy beach habitat also suffered significant oil contamination. Oil still persists in the marshes with little being done to restore these sensitive habitats.

Coastal birds were especially hard hit. These species were exposed to oil as they rooted in the oil-soaked mud and sand to feed on small crustaceans, dive for fish, consume oil-tainted prey, and move through oil-tainted water and vegetation. The litany of ill effects these birds can experience from oil includes hypothermia, drowning, starvation, organ damage, and impaired reproduction. Tragically, for many species the wetlands and beaches now affected by the oil spill were the last bits of unspoiled habitat they had.

The state of Louisiana estimated that more than 130 species of coastal birds were threatened by the BP spill. These include the piping plover, a tiny and critically endangered shorebird, as well as numerous other shorebirds such as terns, gulls, sandpipers, oystercatchers and avocets (to name a few). The list also includes some of the most magnificent wading and wetland birds we know: the roseate spoonbill; the wood stork; and numerous species of ibis, herons, egrets, bitterns, rails and ducks.

Deepwater Horizon explosion photo courtesy U.S. Coast Guard