WASHINGTON — In one of nature's best comeback stories, endangered green sea turtles have multiplied in Florida during the past two decades and are now thriving in protected waters from Melbourne to the Florida Keys, marine scientists have discovered.
Intense conservation efforts have helped these 300-pound vegetarians flourish, with females laying hundreds of eggs along Florida's east and southwest coasts and returning every two or three years to the exact same spot to nest again. Reported nests have increased more than sixfold since 1990.
Their migrations between nesting seasons have been a mystery. But a recent study that tracked a sample of mother turtles by satellite — published last month in the Biological Conservation journal — indicates that green sea turtles spend much of their time foraging on sea grass and algae in or near marine sanctuaries in the Florida Keys.
"They are big, fat and healthy," said Kristen Hart, a research ecologist who led the study for the U.S. Geological Survey. "They seem to be finding what they need here, and that's kind of cool."
One major conclusion: Conservation efforts — especially the marine protected areas in Florida that limit commercial activity and some fishing and boating — are helping save the endangered turtles.
This study and similar evidence from around the world shows the value of MPAs and could inspire attempts to designate more of them along the Florida coast, said Lou Fisher, administrator of the Sea Turtle Conservation Program in Broward County.
Florida's legions of turtle lovers have long backed MPAs, but some commercial interests, including fishermen, oppose the restrictions. Some businesses also object to ordinances limiting bright lights along the beachfront to avoid disorienting hatchlings on their way to the sea. But these limits appear to be helping the turtles.
"It looks like the [conservation] work is very beneficial," Fisher said. "It started out low, but the trend is an increased number of green-turtle nests here and throughout the state of Florida."
Marine scientists now are more worried about other varieties of sea turtles, such as loggerheads, which roam far from Florida and face a wider array of threats, including trawlers and long-line fishing. The green sea turtles, though capable of migrating hundreds of miles, stick closer to home and benefit from the state's protected waters, especially around refuges in Brevard County and the Keys.
Nobody knows how many green turtles live in warm waters around the world, but their nests were sparse enough in the late 1970s to designate them as "endangered" in Florida and "threatened" worldwide. Conservation efforts since then, including creation of three MPAs in Florida in 2009, helped save a turtle with ancestors that go back to the age of the dinosaurs.
By 2011, 10,701 nests were reported on 200 miles of closely monitored beachfront along Florida's Atlantic and Gulf coasts, most of them clustered around the Archie Carr National Wildlife Refuge near Melbourne. That's more than a sixfold increase since the 1,651 counted in 1990.
Statewide nest counts, including the 200 miles of monitored beaches, amounted to 15,352 in 2011. The total included 7,513 in Brevard County, 3,733 in Palm Beach County and 261 in Broward County.
"Finding a green-turtle nest had been a very rare event. We would find only a handful every year," said Barbara Schroeder, the national sea turtle coordinator for the National Marine Fisheries Service, who grew up in Orlando and surveyed beaches in Brevard County as a state marine scientist in the 1990s. "For surveyors now, it's very common."
The recent findings, she said, "clearly show the importance of the Florida Keys and the value of marine sanctuaries that have that extra degree of protection. It underscores the importance of these protected areas and could shed light on additional areas that could be considered."
The latest migration study used satellite telemetry to track tags that were attached to the shells of mother turtles in the Dry Tortugas, just west of Key West. That way their movements can be documented.
This and other recent studies indicate that most green turtles that hatch in Florida forage in the Keys or along the state's east or southwest coasts, though some migrate as far as the Bahamas before returning to their nesting sites. One tagged turtle swam up Florida Bay and into the western Everglades before returning to the Dry Tortugas.
Their biggest threat in Florida comes from boat strikes, because the turtles must surface to breathe.
"They lay lots of eggs across a broad area so they can hedge their bets on making it," Schroeder said. "So it's important to maintain that distribution and ensure that those beaches remain good places for turtles to nest, regardless of how developed the surrounding areas are."
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Green sea turtle
Roots: Sea turtles go back to the age of the dinosaurs.