Some swim more than 6,000 miles – dodging sharks and boats alike on the journey – for the chance to feed in Palm Beach County’s grassy sea turtle haven.
The Lake Worth Lagoon has become a growing destination for endangered green sea turtles coming from Mexico, Costa Rica and the southern reaches of the Atlantic Ocean.
Within the lagoon, sea grass beds around Little Munyon Island near John D. MacArthur Beach State Park have the highest concentration of these two- to three-year-old, vegetarian sea turtles attracted to the submerged food supply and protection from predators that the waterway provides.
Since 2005, scientists have counted more than 500 of the green sea turtles in the lagoon from North Palm Beach to the Boynton Inlet. That includes more than 200 last summer, according to findings presented Thursday.
"What happens here matters," said biologist Jonathan Gorham, who has tracked the lagoon’s sea turtle population since 2005. "Ecologically, it’s interesting (that) what happens in the Lake Worth Lagoon influences sea turtle nesting throughout the western hemisphere."
The success of green sea turtles in the Lake Worth Lagoon also shows good signs for efforts to restore marine habitat and water quality in the local waterway that has been ravaged by waterfront development and polluted stormwater runoff.
Sea turtles are considered the “canary in the coal mine” for the Lake Worth Lagoon, offering a good barometer for the overall environmental health of the lagoon. If sea turtles are thriving, that means organisms lower on the food chain are also thriving.
"We wanted to know a little bit more about how important the lagoon was for turtles," said Paul Davis, of Palm Beach County’s Environmental Resources Management department, which commissioned the sea turtle study. "The results were pretty surprising."
Biologists are finding more sea turtles than expected. The turtles are also a different age range from the adults that come to lay eggs on local beaches and the hatchlings that emerge from the buried nests and try to make their way out to sea.
Gorham and his team last summer looked for turtles from elevated platforms on small boats. They used nets to scoop turtles from the lagoon. The turtles were measured, weighed and checked for signs of disease. Blood samples taken during the 15- to 20-minute exams helped determine where the sea turtles came from.
Water pollution, fishing lines and other trash floating in the ocean, ocean front development and commercial fishing are among the man-made threats to sea turtles.
Environmental restoration projects in the Lake Worth Lagoon since the late 1990s years seem to be making the waterway more attractive to turtles.
Clearing out exotic plants and planting mangroves and also creating new oyster beds and sea grass beds are efforts aimed at improving both water quality and marine habitat in the lagoon.
Biologists have determined that during the spring and summer, the lagoon is an important developmental habitat for juvenile green sea turtles that come to feed for a while before moving back out to sea, said Gorham, of the Jensen Beach-based Inwater Research Group.
"It’s a pretty small, discrete area that (has) a tremendous abundance of green sea turtles," Gorham said about the waters around Little Munyon Island. "Small turtles are feeding and growing and then they move off."
Cause for concern remains for sea turtles in the lagoon.
Nearly 40 percent of the green sea turtles examined by the research teams suffered from a tumor-causing disease called fibropapillomatosis. Those tumors, which environmental groups blame on water pollution, can be deadly for turtles if they spread too far.
Also, more than 60 percent of all sea turtles found dead or injured in the lagoon and ocean waters off the coast of Palm Beach County have evidence of boat strikes, according to the county.