MELBOURNE, Fla. — As the sun rises over sea turtle nests across the Space Coast, biologists are seeing new glimmers of hope.
Many feared for the future of Florida’s three most endangered types of sea turtles – green, loggerhead and leatherback turtles – but this year, evidence suggests they are bouncing back.
This is especially true along Brevard County’s Space Coast, where astronauts have launched to the moon and where these prehistoric leviathans have laid countless eggs.
“Yes, in general we had a good season for leatherback turtles (a new record, although the numbers are still low given that we are in the northern part of where leatherback turtles nest along our coast),” wrote Kate Mansfield, an associate professor at the University of Central Florida.
“Over the decades, green sea turtles have made an incredible comeback,” she added, attributing conservation action. “Loggerheads usually hold their own.”
But a year doesn’t make a trend, Mansfield warned. “Sea turtle work is ‘slow science’ and we need decades of data before we can truly assess population trends,” she noted.
Many reasons for concern remain: Sea turtles today lay their eggs in holes in warmer sands, which means few or no males hatch and less genetic diversity, sending recent population rebounds in reptilian tendrils of uncertainty. As with alligators, the temperature of the incubating egg determines the sex of a sea turtle.
“Generally speaking, it is certainly concerning that increasingly hot summers are altering the sex ratios of hatchlings from our beaches, producing more females,” Mansfield said.
“There are a number of factors that play into the temperatures that turtle eggs experience during incubation – the brood depth, the rainfall, the color of the sand or the time of year the nest is incubating. .”
Research in South Florida found that in the warmer beach sands of recent summers, almost all sea turtle hatchlings are female. Scientists suspect similar, less extreme changes in sex ratios along Space Coast beaches, but lack the data to prove it.
There are also other problems.
Hotter summers also mean thicker and thicker seaweed so hatchling turtles can sail to reach the Gulf Stream, where seaweed is less of an obstacle and more of a vital food source and place to dodge predators.
Seaweed isn’t the only thing turtles avoid. They must also avoid beach furniture, fishing nets, and some perish by swallowing tar or floating plastic.
Green sea turtles defy odds
Paddling against these ever-stronger currents of challenge, only the fittest survive. From each hatch, estimates range from one in 1,000 turtles to one in 10,000 surviving long enough to become an adult turtle.
But the good news is that one species in particular defied the odds.
In the 1970s, biologists found only a handful of green sea turtle nests at Archie Carr National Wildlife Refuge and the Melbourne Beach area, both located in Brevard County. Many biologists thought the greens would soon disappear, but decades of conservation action have paid off.
Commercial fishing pressure, disease, and habitat loss have reduced reptile numbers. Hatchlings roam the roads because of the bright lights on the beach. In countries where their sweet-tasting meat is relished by locals, the perils are worse.
But the number of green sea turtle nests on key beaches, which include more than a dozen miles of shoreline in Brevard, has increased eighty-fold since standardized nest counts began in 1989, according to Florida Fish and Wildlife Conservation Commission.
Greens are just one of three species that use the Carr Refuge as their primary nesting location. Endangered Leatherback Sea Turtles and Threatened Loggerhead Sea Turtles also nest on Brevard beaches and have shown promising long-term trends, despite fluctuations in recent years.
Loggerheads are the most abundant sea turtle species that nest in Florida. In 2012, loggerhead sea turtle nesting hit a nearly 24-year high along Florida beaches, according to state biologists, doubling the number of nests the reptile had dug five years prior.
Hot sands impact turtle hatchlings
But loggers and other sea turtles face darker and warmer weather, warn wildlife biologists, pushed by global warming.
Darker sand absorbs more heat from the sun, creating changes in turtle eggs that result in more females. If the beach sand is too white, there is more reflection and cooler sand, which means the number of males increases.
Sand 82 degrees Fahrenheit or hotter tends to make a woman hot. Below this temperature, males become more susceptible. No one knows exactly why. The theory is that a mixture of hormones sends chemical signals, triggered by the temperature of the beach sand, that turn on some genes but turn off others. A sea turtle’s sex is determined about 40 days after the start of its incubation period, which averages about 60 days.
Enter the dredges and trucks that deposit countless cubic yards of sand on Florida beaches after every big storm.
Biologists fear that if the re-fed beach sand is too light or too dark, it could skew the turtles’ sex ratio, threatening the species’ long-term survival. Too little of either sex could thwart reproduction and genetic diversity. A smaller mating pool for turtles means less resilience and a higher risk of birth defects and disease.
A 2008 study by Florida Atlantic University found that up to two males for every five female loggerheads hatch on Florida sands, which is considered a healthy ratio for the endangered species.
Nighttime darkening of sand color on Brevard beach restoration projects has sometimes caused local residents to see red.
The new sand being pumped to Brevard beaches comes from an area about five miles off Cape Canaveral called Canaveral Shoals.
County contractors test the sand daily to ensure it is the correct grain size and color and has the correct carbonate content. The sand looks darker because it’s been on the ocean floor for years and isn’t lit by the sun, but biologists say sea turtles have evolved and adapted to the range sand colors here.
Sargassum algae: too much of a good thing?
Sea turtles are also having to deal with thicker-than-usual Sargassum seaweed this summer. The Caribbean Sea delivers the seaweed seasonally to the Gulf Stream and then to the beaches of central Florida.
Oceanographers expect sargassum and other macroalgae to thicken on our beaches each year, due to increased coastal runoff and warmer waters driven by climate change.
“Sargassum in the surf zone is actually a bit more of a threat to at least hatchlings when it washes ashore,” Mansfield said.
Hatchlings are “wired” to swim offshore to where they stay for at least a few years.
“But, that first push to go overseas is essential,” Mansfield added. “If they encounter obstacles, like piles of sargassum, that means they need to expend more of that precious energy that should be spent swimming – and offshore, away from coastal predators.”
It’s especially daunting for newborns who are half the size of a deck of cards, Mansfield said.
“So even a foot-tall pile of sargassum would be like trying to scale a two- to three-story building. Also, there’s a risk of newborn babies getting stuck,” he said. she declared.
But biologists like Mansfield continue to testify and document a species that is about to keep the sun from setting on its species, especially the mothers.
“For larger turtles, it’s less of an issue because nesting females can usually cross, assuming it’s not a huge amount,” she said.
Turn off your beach lights
Beachfront homes and businesses must turn off or shade their lights during sea turtle nesting season, which officially begins Sea turtle nesting season begins March 1 for Florida’s Atlantic Coast. Brevard County has a “blackout” ordinance in effect from May 1 through October 31 that requires all lights visible from the beach to be covered, blocked, relocated, or turned off from 9 p.m. to 5 a.m. This includes flashlights, cell phones and red lights. Although sea turtles are less affected by red light, they still see it.