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Easy Fix For Threatened Sea Turtles?

Easy Fix For Threatened Sea Turtles?

Shading and environmental controls may help save the population.

The Lightworks via flickr

Tuesday, July 10, 2012 - 18:15

Joel Shurkin, Contributor

(ISNS) -- Changes in climate and environmental threats have put all seven species of sea turtles on the endangered list, and while the threats seem to grow, saving the turtles from some dangers may not be expensive or complicated.

Two teams of scientists have published reports on new, growing threats to the animals -- and in both cases, the solutions to the problems are cheap and have already made a difference.

A team from Princeton and Drexel Universities and several government laboratories has found that rising temperatures on the nesting beaches on the coast of Costa Rica are jeopardizing the breeding population. A second team of scientists from federal, academic, and nonprofit organizations has warned that levels of the chemical compounds known as  perfluoroalkyls, or PFCs, known to be toxic in laboratory animals, are building up in five of the species.

In the case of the rising temperatures, the danger simply disappears by adding a little shade. To deal with the increasing PFCs, the solution is to stop making the stuff.

Female sea turtles crawl onto the beaches, often where they were born, to lay 100-120 eggs in the sand. Hatchlings emerge after 60 days and race through a gauntlet of predators to the water. Maybe one in 100 hatchlings survives to maturity.

The animals have been threatened for years by egg poachers -- human and animal -- and by getting caught and drowned in fishing nets.

The Princeton-Drexel team studied the plight of leatherback turtles on Costa Rica's western coast, where they are particularly threatened. Using internationally assessed climate models; they believe the turtles could be wiped out in that area by the end of this century. The beaches are projected to get hotter and drier.

Their work is published in Nature Climate Change.

Vincent Saba, a fisheries biologist with NOAA's National Marine Fisheries Service center in Princeton, said the turtles, which have been around for some 90 million years, adapted to changing environments in the past. What makes the current situation dire is the speed of the change.

"Natural selection works with individuals, not populations," Saba said. "You need to have a substantial amount of time for each generation to adapt to a changing climate."

Leatherbacks work on turtle time. They mature late, possibly 15-29 years.  They reproduce every 2-7 years. No one knows exactly how long they live, but experts estimate between 30-50 years or more. Other turtle species can live to more than 100 years, Saba said.

By the end of this century, Saba said, there would have been only a few generations, not long enough for them to adapt. They would have to move their nesting beaches elsewhere, or come onshore earlier in the season.

Saba emphasizes that the research was valid only for the beach he researched, on the eastern Pacific. Leatherbacks are doing better in the Atlantic, although what happens in the Pacific could eventually happen there. Temperatures are expected to rise worldwide.

There is no evidence that the Costa Rica population on this beach have yet actually been affected. Saba and his colleagues were projecting what could happen according to the models.

The solution? Nest shading. Nest corrals or enclosures were originally designed to keep insect larvae off the eggs as well as raccoons and dogs. The corrals offer shade as well, cooling the temperature of the sand. Studies done on Atlantic beaches show artificial shading also cools the nests, Saba said. That could work in the Pacific as well.

Meanwhile, another team of scientists has found that pollution from PFCs is reaching possibly toxic levels in five of the seven turtle species: the green, hawksbill, leatherback, loggerhead, and Kemp's ridley. Their work is published in the journal Environmental Toxicology and Chemistry.

PFCs are used in stain-resistant clothing, firefighting foams, food processing, nonstick cooking utensils, and in plastics manufacturing.

The researchers did not perform toxicological tests on the animals, which were caught in the waters of the southeastern U.S., to see whether they actually were harmed. But they found levels in the turtles approaching concentrations known to harm rodents and fish in laboratories, said lead scientist Jennifer Keller of the Hollings Marine Laboratory in South Carolina.

All five species had levels associated with suppressed immune systems, and three had levels either suggestive of risk for liver and neurobehavioral toxicity or thyroid disorders.

Alan Goldberg, a toxicologist at Johns Hopkins Bloomberg School of Public Health, said it was an interesting paper, but he was skeptical of extrapolating from laboratory rodents to the turtles.

"[Turtles'] metabolism of these compounds may -- and I say may -- be completely different from rodents," Goldberg said.

Keller said the researchers had no choice; no one has produced a model relating rodents to reptiles or amphibians, although her group is working on one.

The good news, however, is that the solution to the problem may be simple. In 2001, 3M Co., one of the main manufacturers of one type of PFC, perfluorooctane sulfonate, halted manufacturing of the substance.

Keller and her team found last year the amount of perfluorooctane sulfonate in turtles had actually declined from 2001-06.


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Joel Shurkin, photo by Abigail Dunlap

Joel Shurkin is a freelance writer in Baltimore who has also taught journalism and science writing.