5 of The World's 7 Sea Turtles are Threatened by the BP Gulf Oil Spill

The BP Gulf oil spill is threatening not only fish (and fishermen), birds and marine mammals, but sea turtles. As both the slick on the surface and the plumes deep underwater spread across the Gulf of Mexico, and the duration of the spill extends from days into weeks into months, more and more turtles are put at risk. For sea turtles in the Gulf, it's a threat they can't necessarily survive. All of the five species that live out some portion of their lives in the Gulf are endangered or threatened species. There are only seven species of sea turtle worldwide, making the Gulf's habitat critically important for the conservation of the world's turtles.

"Sea turtles can suffer both internal and external injuries from contact with oil or chemical dispersants," said Elizabeth Wilson, a marine scientist who is the fisheries campaign manager at Oceana, the world's largest ocean conservation organization. "In addition to regulating bycatch in commercial fisheries and protecting critical habitat areas, the U.S. government can now add 'preventing future oil spills' to its list of essential sea turtle protections."

Oceana is urging President Obama and Congress to permanently ban further offshore oil drilling, not only in the Gulf of Mexico, but along the Atlantic Coast and in the Arctic off Alaska as well.

What follows are profiles of the turtles at risk. Already nearly three dozen oiled turtles (like the Kemp's Ripley turtle pictured here) have been found alive since the spill; more than 320 sea turtles have been found dead. While the loss of wildlife from the oil spill is a disaster unfolding relatively swiftly, slow-moving disasters are also a consequence of our reliance on fossil fuels like oil and coal: Ocean acidification and global warming are two major long-term threats to the health of the oceans as well, including the world's dwindling sea turtle populations.

The National Oceanographic and Atmospheric Administration had this to say about sea turtles and oil in a 2006 book: "While the probability of any given spill affecting sea turtles is low, even one spill—if it occurred at just the wrong time and place—could be catastrophic to one of these endangered species. Sea turtles are likely to be at greatest risk from oil spills, for example, when they are gathering in a particular area to nest, right after hatching, and when foraging in ocean convergence zones."

The Gulf of Mexico is such a place, and this – nesting and hatching season – is such a time.

Loggerhead Turtle (Caretta caretta)

The most abundant sea turtle in U.S. waters, the loggerhead is found worldwide in tropical and temperate waters, and yet it is has been listed as a threatened species since 1978 (220 years after first being described by the father of taxonomy, Carl Linnaeus) and its population continues to decline. Pacific loggerhead turtles, which migrate an incredible 7,500 miles, have declined 80% in 25 years, and though the Atlantic or Indian ocean populations have not declined as rapidly, they are in retreat.

Prime nesting for loggerheads in the Atlantic occurs in June and July from Virginia to Alabama, but extends to a lesser extent from April through September and throughout the Gulf of Mexico to Texas and the Yucatan Peninsula. Populations of nesting turtles have been steadily declining, and scientists have recently confirmed that loggerheads around the world live in distinct sets, so the loss of turtles in U.S. waters, for instance, is unlikely to be replaced with turtles from other waters.

So why are they threatened? Beach nesting habitat has declined, predators have proliferated because of human activity and at sea, fishermen targeting other fish often catch loggerheads as "bycatch," and because some nations still hunt turtles for meat. Finally, because they take 35 years to reach sexually maturity.

The Gulf oil spill may be particularly harmful because breeding-age females that nest in the Gulf of Mexico, and many from the largest nesting colony in the U.S., on peninsular Florida, congregate in Gulf waters. Many juvenile turtles also spend a significant amount of time in the near-shore waters of the Gulf of Mexico. Nesting beaches may also be oiled, and newly emerged juvenile turtles are known to use the Gulf loop current; oil has already reached this river of water, carrying it to Florida.

Green Turtle (Chelonia mydas)

Unique among sea turtles for its vegetarian diet, green turtles evidentially find algae and seagrass quite nutritious, since they are the largest of the hard-shelled sea turtles, growing from tiny two-inch hatchlings into 300-plus-pound behemoths.

Green turtles are widespread – nesting in 80 countries and living offshore as many as 60 more – but was listed as threatened throughout its range by the U.S. government in 1978; it is listed as endangered in Florida and on Mexico's Pacific coast, and global conservation organizations and the U.N. consider it endangered worldwide. Nesting numbers have declined 50% or more in the last century. Why? Primarily hunting, of turtles and their eggs, and fisheries bycatch. The Gulf of Mexico and Florida are critically important habitats, though they can be found as far north in the U.S. as Massachusetts.

It may take as little as many as 50 years for an individual to reproduce. The loss of a generation of turtles to the oil spill could set back recovery efforts significantly.

Kemp's Ridley Turtle (Lepidochelys kempii)

The smallest sea turtle in the world, Kemp's Ridley turtle adults still weigh in at 100 pounds, and live only in the Gulf of Mexico and along the U.S. East Coast. A critically endangered species, Kemp's Ridley turtles have one of the most unusual synchronized nesting habits, with wave after wave of females washing ashore in and around Rancho Nuevo, Mexico, on the Gulf Coast from May to July. There, it is called the "arribada" or "arrival."

It's the reliance on one nesting area (95% of nesting happens there) that led to a precipitous decline in their numbers, since historically local people harvested the eggs for food; since hunting has been curtailed, fisheries bycatch has taken a toll, but populations have shown signs of rebounding. It's the outflow of hatchlings that puts Kemp's Ridley turtles at risk from the BP oil spill. The young enter prevailing currents, like the Gulf Loop, and are carried throughout the Gulf and into the Atlantic, and they drift with seaweed on the surface for as long as two years, where they could be easily caught in an oil slick.

Hawksbill Turtle (Eretmochelys imbricata)

Though its name comes from its sharp beak-like mouth, the Hawksbill mainly feeds on sponges and other invertebrates in coral reefs. Its beautiful tortoiseshell coloring continues to make it a target of hunters, which can legally catch them in some of the Caribbean. Fisheries bycatch is also a problem, but loss of coral reefs is the largest threat to their existence. It's been listed as an endangered species since 1970.

Found worldwide, Hawksbill nesting is especially abundant in Puerto Rico and the Caribbean; they nest rarely but are found in the U.S. along the Gulf Coast, especially in Florida and Texas, and they range widely – with migrations documented of over 1,000 miles.

If nesting beaches and coral reefs in the Florida Keys are affected by the BP oil spill, these turtles could lose significant U.S. population.

Leatherback Turtle (Dermochelys coriacea)

The largest sea turtle, the only sea turtle without a hard shell, the only sea turtle to tolerate cold water, and the world's largest reptile, the Leatherback can reach six feet in length and weigh 2,000 pounds – almost as much as a Smart car.

Listed as an endangered species in 1970, Leatherback turtles have declined 80% in the Pacific, but population declines in the Atlantic have been less severe. The biggest threat to the species' survival is hunting and fisheries bycatch.

While the Gulf of Mexico is not the most important habitat, these long-range migrants can be found throughout the Gulf.