Sea turtle nesting season begins; beach work is weeks behind
Beach renourishment in Boca Raton
“It’s good they’re doing the renourishment,” says Kirt Rusenko. He’s a Marine Conservationist with the Gumbo Limbo Nature Center in Boca Raton, Florida.
He’s talking about the $9.5 million dredging project underway right out the center’s front door, and by extension, a similar project in Juno Beach. His stance might seem surprising, given that both projects are now certain to push well into sea turtle nesting season, which begins March 1 every year. But he’s a realist, and he sees beach-widening as the lesser of two evils.
“I’m a proponent because the only other choice would be seawalls,” Rusenko says. And seawalls would leave nesting turtles nowhere to go. “I just wish it would go a little faster.”
The contractor for the Boca project, Great Lakes Dredge and Dock Company, expects to have things wrapped up by the end of March. That’s according to Jennifer Bistyga, a Coastal Project Administrator for the city. And, she reassures, turning the nesting ground into a construction site won’t cause any problems.
“If anything was ever found inside the construction zone,” Bistyga says, “we’d stop immediately to make sure there’s no impact.”
Dredging barge off Boca Raton
The Boca operation, unlike the hopper dredge off Juno Beach, is basically just a big vacuum, continuously sucking sand off the bottom and depositing it on the beach. In fact, she says, the 24/7 rumble of the machinery underwater works in favor of wildlife.
“The vibration that’s going on beneath a hydraulic dredge tends to keep turtles and other critters away,” Bistyga says.
There’s something else tempering Rusenko’s concern about the violation of the annual nesting deadline. He knows that critically-endangered Leatherbacks are usually the first sea turtles to come trudging ashore. And he knows far more of those head for Juno Beach than for Boca.
“They get 10 times the Leatherbacks we do,” Rusenko says.
Dredge pipe in Juno Beach moves water and sand with a muted ‘whoosh’
Up in Juno Beach, big sections of the project are finished. Other places, massive pipes run parallel to the water line, and bulldozers roar around. And it’s going to go on for awhile. The latest estimates have construction violating turtle season by at least six weeks.
“I think the latest completion date is sometime in the middle of April,” says Palm Beach County environmental analyst Reubin Bishop.
“They’re almost halfway done. They’re within a thousand feet of the pier, which is what I consider halfway,” Bishop says. He’s checking the latest reports and emails for a completion estimate, and there’s a pause.
“Off the beach by April 20th,” Bishop confirms. Or a little more than seven weeks past the point when humans are urged to stop any sort of activity that might disturb the nesting Leatherback, Loggerhead and Green sea turtles. Even street lights are turned off in the area so the turtles don’t confuse incandescent bulbs with stars. The South Florida beaches are some of the turtles’ last safe nesting grounds.
Sections of 36” pipe wait to be fastened together; Juno Beach Pier in the background
Until the dredging is over, experts will comb the beaches looking for disoriented turtles or nests that need to be moved to some safer stretch of sand. But even in the hands of the most skilled conservationists, that kind of patrolling just solves some problems... while it creates others.
Back at Gumbo Limbo, Kirt Rusenko says the renourishment raises issues for the turtles that no one has addressed yet.
First, he says, the turtles seem to avoid the new sand. Usually, on an undisturbed beach, about half the turtles that come ashore make nests. The other half just turn around; they’re called “false crawls.” That’s a ratio of one to one. But the success rate is much lower where the sand has been pumped in from the ocean bottom. (See Gumbo Limbo research abstract here.)
“In a renourished area we’re seeing seven false crawls” for every nest, Rusenko says, or a ratio of seven to one. Scientists suspect higher salinity prompts the turtles to avoid the beach. Rusenko says six to eight inches of rain eventually solves the salinity problem, and the turtles accept the beach again.
But then there’s the promise that if nests are found in the renourishment area, they’ll be moved somewhere safe.
Rusenko, whose own organization would be involved in such a move, says it’s not that simple.
“Sea turtle eggs are very sensitive to movement,” he says. “Moving them can cause up to 30 percent mortality.”
So when dredging is allowed in sea turtle nesting season, the only help also hurts.