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How rising seas could sink the sea turtle

BY   September 16, 2015 at 5:10 PM EDT
 
Editor’s note: This story is part of a series, The Wild Side of Sea Level Rise, which explores the basic research behind ocean expansion and its impacts on coastal ecology.

It was a moonless Friday at the Archie Carr National Wildlife Refuge in Florida, and a loggerhead sea turtle was giving birth. I watched as her goo-covered eggs dropped in threes, each clutch landing in the sand with a wet plop. The sound echoed against the crashing waves.

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She seemed ambivalent to my voyeurism. A loggerhead, like any sea turtle, is wary of predators while picking a nesting site onshore. If unconvinced of the spot’s safety, she’ll turn tail and head back to the ocean. But once laying begins, nothing will stop her from dropping all her eggs and concealing her nest with sand. It’s a version of cruise control from the dawn of the sea turtles 120 million years ago. A primordial commitment to protecting her young, fortified by generation after generation returning to the beaches of one’s foremothers.

Archie Carr is an epicenter for this way of life. Loggerheads plant between 50,000 to 100,000 nests on Florida beaches each year — about 80 percent of the Atlantic population— but the Archie Carr refuge hosts the largest batch. One out of every four of those turtles nests on this 20-mile section of sand.

They’re not alone. Thousands from other sea turtle species join them. Giant leatherbacks with striped, referee uniform-like shells flap onto the beach with green turtles, Kemp’s ridleys and hawksbills.

It’s their birthright, and it’s slowly eroding.

You’ve heard the stats. Seas are rising as hotter temperatures melt glaciers and physically expand the ocean. By 2100, seas are expected to rise by three feet across the globe, and places like the U.S. eastern seaboard will face up to 15 inches more. Last month, NASA scientists reported that sea levels might rise even faster than initially predicted.

“Even if we were to reduce greenhouse gas emissions today or somehow mitigate temperature change, there is going to be continued sea level rise and continued warming for the next hundred or couple hundred years because of the inertia in the oceanic and atmospheric systems,” said NASA glacier scientist Tom Neumann. “So in that sense, we’ve already bought into continued sea level rise and continued warming.”

In the face of an unstoppable train, it’s natural to focus on what this means for us, for humans. About 160 million Americans — 53 percent of the population — live in coastal regions, and in cities like Miami and Annapolis, Maryland streets already flood with many high tides.

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But long before our cities wash away, thousands of critters and plants will feel the blunt hammer of these rising waves. The slow creep of rising tides and the blasts of storm surges won’t just wash away habitat. The rushing water is changing how these organisms exist, and may potentially decide whether they exist at all.

Sea turtles mostly live at sea, but return to land to lay their eggs. This habitat is threatened by rising water, but there’s another problem: females are running dangerously low on mates.

Hot girls, cool guys

The Gumbo Limbo Nature Center takes its name from the scraggly trees that populate its front lawn. Those and palm trees conceal the facility from drivers and bike riders coasting down the A1A beach highway in Boca Raton, Florida. Creamsicle rays of sunlight filter through the branches onto large sculptures of sea turtles. Founded in the 1970s, the nature center watches over wildlife on the city’s five miles of beach, with the help of its next-door neighbors, the Florida Atlantic University Marine Research lab.

It’s at that lab that we met marine biologist Jeanette Wyneken, who spends much of her time dwelling on sea turtle sex. Not copulation, but the physical sex of the reptiles.

“What we’ve been doing across this beach for the last 13 years is documenting sex ratios of little loggerheads like these guys,” she said, plucking from a tank a hatchling with a brown underbelly that resembled a gardener’s muddy shirt.

Loggerhead turtle — Biologist Jeanette Wyneken holds a young loggerhead turtle at the Florida Atlantic University Marine Research lab. Photo by Mike Fritz.

The sex of the sea turtle is determined by its environment. Hot weather produces more females, while cooler temperatures make more males. With global warming and increased drought conditions, Wyneken and her team have seen an extreme and disproportionate shift in the pattern toward females.

“In 2010, we did not see a single male. That was a drought year,” Wyneken said. Among thousands of loggerhead nests in southeast Florida that year, both near Boca Raton and a sister site at Juno Beach, it’s likely that not one male hatchling was present.

But a mother sea turtle nests multiple times in her life, so what’s the harm if one nesting season’s a bust?

Too many generations of unisex sea turtles could be devastating for the animals. Loggerheads are threatened in the Northwest Atlantic, meaning they’re likely to become endangered in the foreseeable future. Other species nesting off Florida — greens, leatherbacks, hawksbills and Kemp’s ridleys — are endangered. This is in part because few sea turtles survive from egg to adulthood. Some eggs never hatch or are nabbed by skunks or foxes. Hatchlings make a mad dash for the sea immediately after birth, but many are consumed by seagulls or crabs.

“In the case of the loggerhead, if you do a back-of-the-envelope calculation, we’re looking at about 1 in 7,000 making it to adulthood,” Wyneken said. “So she’ll have to commit to over 10 nesting seasons, which, in the case of a loggerhead is a 20- or 30-year period, just to replace herself and maybe one mate.”

A trend toward too few males may also weaken the population’s genetic diversity, making the turtles more prone to disease.

Young loggerhead sea turtles at the Florida Atlantic University Marine lab in Boca Raton. Photo by Mike Fritz

Young loggerhead sea turtles at the Florida Atlantic University Marine lab in Boca Raton. Photo by Mike Fritz

If drought is one edge of the sword threatening turtle diversity, then storm surge is the other. An uptick in storm surges in recent years means that more nests are flooding, which suffocates the eggs or washes them out out entirely. We walked along the beach with Wyneken and her colleague Kirt Rusenko, marine conservationist for the city of Boca Raton and the Gumbo Limbo Nature Center, and stood about halfway between the crashing waves and bottom edges of the dune.

The beach is narrow — less than 30-feet wide from surf to dune in spots — and the sand doesn’t pile high above the water line. Any small rise in sea level combined with a storm surge is going to send water all the way to the dune. Huge waves from Hurricane Sandy covered the entire beach in 2010, to the point where it carved away at the dune, Rusenko said. The city had to ship in sand to pack against the foot of the dune to keep it from collapsing.

As Rusenko’s arm swept to the upper edge of the beach and the dune, one could easily picture the impact. All the sea turtle nests — from midbeach to the foot of the dune — covered in water. Water doesn’t just wash away the eggs, it suffocates them, especially at late stages of development when they’re pulling a lot of oxygen through their shells.

And it’s not just Sandy. In recent years, Wyneken and Rusenko have witnessed storms 80 miles away in the Bahamas create surges that shot all the way up into the dune.

Due to the rising threat of tidal and storm surges, scientists daily are relocating sea turtle nests in danger to areas further up the beach. One of Wyneken’s graduate students — Alex Lolavar — takes this opportunity to examine the “hot girls, cool guys” phenomenon in the wild.

Does more water mean more males?

Due to an increasing number of storm surges, researchers from Florida Atlantic University and Gumbo Limbo Nature Center relocate nests in danger of being washed out. Photo by Mike Fritz

Due to an increasing number of storm surges, researchers from Florida Atlantic University and Gumbo Limbo Nature Center relocate nests in danger of being washed out. Photo by Mike Fritz

Jeanette Wyneken and Alex Lolavar prep an artificial nest for relocated sea turtle eggs. Lolavar uses the opportunity to perform an outdoor experiment on sex ratios. Photo by Mike Fritz

Jeanette Wyneken and Alex Lolavar prep an artificial nest for relocated sea turtle eggs. Lolavar uses the opportunity to perform an outdoor experiment on sex ratios. Photo by Mike Fritz

Leatherback turtle being measured with calipers at the Florida Atlantic University Marine Research lab. Photo by Mike Fritz

Leatherback turtle being measured with calipers at the Florida Atlantic University Marine Research lab. Photo by Mike Fritz

In the lab or extremely hot drought conditions, this temperature relationship is well defined. Add heat, get females. But sometimes, in natural conditions, it’s murkier. In some seasons, scientists record hot temperatures that should produce all females based on lab data, yet the field measurements note a smattering of males. One theory is that rainfall may play a role by cooling a nest, but Lolavar and Wyneken suspect a more nuanced relationship. This is because they’ve found that years with greater rainfall than average tend to produce more male hatchlings, regardless of temperature inside the nest. Their hypothesis: Moisture or humidity might be an independent switch for turtle sex.

To test the idea, the team, led by Lolavar, has created an outdoor experiment that involves relocating loggerhead nests that are too close to the high-tide line and in danger of washing out. The night after a laying, Lolavar splits each nest in half — each contains about 100 eggs — and then digs two artificial nests. One of the resulting nests recieves of daily dose of “rain” via a sprinkler; the other is left dry.

When the hatchlings emerge, the team collects 10 hatchlings from both the wet and dry nests — 20 overall — to raise in the lab. Once the babies are old enough — 2.5 months on average — the researchers will assess their sex. Assessing sea turtle sex is not as simple as just flipping them over. In fact, in the past, the only way to determine gender was via dissection.

“The traditional way of doing this work was to sacrifice a bunch of hatchlings, but that’s not very popular. And it’s kind of counterproductive if you’re working with an imperiled species,” Wyneken said.

So from 2002 to 2004, Wyneken’s team tackled the problem by developing a non-destructive way to gauge the sex of sea turtle hatchlings. The procedure is akin to laparoscopic knee surgery. The scientists use a “tiny telescope” — a fiber optic camera — to examine the sex organs of young hatchlings without harming them. Then, once the turtles are old enough, typically three to four month old, scientists release them into the ocean.

This extra degree of care isn’t unusual for Wyneken’s lab; they specialize in it. For instance, it’s the only lab in the world, as far as she knows, that raises leatherback turtles in captivity. That’s hard partly because the turtles don’t stop swimming…even when they’re slumbering, Wyneken said. To keep leatherbacks from banging against their tank walls until the point of injury, the researchers stick little harnesses to their backs with a string attached to the center of a pole that runs over the tank. They paddle with endless strokes. Flap after flap.

Scientists attach a harness to baby leatherback turtles to prevent them from banging into the tank walls while swimming. Image by Mike Fritz

Scientists attach a harness to baby leatherback turtles to prevent them from banging into the tank walls while swimming. Image by Mike Fritz

Lolavar’s study is ongoing, but if moisture dictates sex, the result would add an interesting twist to the turtle’s global warming saga. It would suggest that the turtles have already adapted in part to sea level rise. Rapid sea level rise has happened several times over the loggerheads’ 60-million-year evolution. The last major glacier melting event, which occurred some 8,000 years ago, elevated ocean water by 21 feet in 140 years. (We’ll face close to a six foot rise, in some places, by 2100). So perhaps sea turtles evolved this moisture switch to handle former surging seas.

However, this adaptation may not save the sea turtles from rapid beach erosion.

Ebb sans flow

Beach erosion isn’t unique to Boca Raton — it is striking most of the Florida peninsula.

“That’s what we see in the Archie Carr National Wildlife Refuge. We’ve lost several meters of beach just over the last 20 years,” said biologist Joshua Reece at Valdosta State University in Georgia.

The redhaired Reece reflects on the sea turtles’ situation on the balcony of retired colleague and mentor Llewellyn Ehrhart, a biologist whom everyone calls Doc. Ehrhart resembles a silver-haired version of MacGyver. Crickets buzz around us in the sweaty afternoon heat, while Ehrhart and Reece banter about the wildlife on this barrier island. A gopher tortoise has apparently taken residence in the sandy dirt, burrowed underneath Doc’s driveway.

Doc began studying the shores of Melbourne Beach in 1982, nearly a decade before the Archie Carr refuge was officially established as safe haven for sea turtles and other wildlife. In 2012, Doc and his colleagues at the University of Central Florida teamed with Reece, who studies vulnerabilities in ecosystems, to examine how loggerhead nesting patterns had changed over the previous two decades. Since Archie Carr is a focal point for loggerhead reproduction, small shifts could have a major impact on nesting success and the species.

 Biologist Joshua Reece (right) and Llewellyn "Doc" Ehrhart chat about sea turtle nesting at Archie Carr National Wildlife Refuge. Photo by Mike Fritz

Biologist Joshua Reece (right) and Llewellyn “Doc” Ehrhart chat about sea turtle nesting at Archie Carr National Wildlife Refuge. Photo by Mike Fritz

The study isolated three major threats to sea turtles nesting in the refuge and throughout Florida: coastal development, increasingly warming temperatures and sea level rise.

“It’s really important that we look at those three things at the same time, because they have synergistic effects,” Reece said.

Land use by humans pairs with sea-level rise to create a vise on sea turtle nesting. Typically, beaches are dynamic. As waves rise, the dune can flatten and replace the sandy beach, and then the inland area becomes the dune. However, because people have hardened the shorelines by laying cement foundations for beach condos or built asphalt coastal highways, this shifting cycle doesn’t occur anymore, meaning the beach gets narrower with each passing tide and storm.

“Climate change is nothing new to sea turtles,” Reece said. “They’ve been here for hundreds of thousands of years, and they’ve dealt with climate change more rapid than what we’re seeing today. What they haven’t dealt with is climate change in the context of human infrastructure.”

Due to global warming, loggerhead sea turtles are nesting earlier in the year than before, but they also appear to be shifting northward at the refuge. It isn’t clear yet if this shift is happening statewide, but at Archie Carr, Reece’s research has found that the nests are moving north. As a result, more of their nests are landing in narrow, heavily eroded beaches that can’t ebb and flow due to urban development.

This land shortage comes at a time when turtle numbers are rising. Conservation policies over the past few decades have banned turtle harvesting for food, and fishermen have modified their deep sea nets, so they no longer ensnare sea turtles. As a results, sea turtle nesting in Florida seems to be rebounding from the historic lows recorded during 2000 to 2010. In fact, this year marked the strongest nesting summer on record.

But that means more turtles occupying a smaller and smaller habitat. And if sea levels rise by 1.5 feet, as climate scientists predict they should by 2100, then Reece and his colleagues predict that 43 percent of the turtles’ nesting ground could disappear.

“As these beaches become increasingly narrow, there’s simply not enough room for as many sea turtles that nest on this beach to lay nests without actually digging up an existing nest and disrupting those eggs,” Reece said. “Also, if the turtles shift to new nesting grounds, the refuge doesn’t move with them. We need proactive strategies to shift those wildlife protections too.”

Total nests and washouts on the five-mile stretch of Boca Raton

 Total Nests
 Lost Nests due to Washouts


A $2 billion band-aid

Florida residents have limited options for abating sea level rise, and most are unsustainable or detrimental to turtle conservation.

Beach renourishment offers a buffer for the seas and temporarily rebuilds turtle nesting grounds, but it is costly. Most nourishment projects last between five to 10 years and cost millions of dollars. Over the last 25 years, Florida has spent more than $2 billion to renourish beaches with 250 million cubic yards of sand, according to the Western Carolina University’s Program for the Study of Developed Shorelines. Yet, storm surges and high tides will worsen, requiring even more renourishment as time passes.

“It’s simply not a viable long-term strategy to continue pumping that sand up onto the beach. As sea levels rise, we can’t keep pace,” Reece said. Plus, after each renourishment, it takes two to three years for the sand to settle or “equilibrate”, and during this time, more nest washouts occur.

Wyneken said shipped-in sand can make the beach harder, as hard as concrete, and that can impede a mom’s ability to dig a nest. A sea turtle nest is typically shaped like an upside-down lightbulb, but due to this beach renourishment, it’s not uncommon to find nests that look like toilet plungers. Misshapen nests — with a narrow neck and wide base — mean that the hatchlings have a smaller escape route. Many can’t get out, and the result is a goopy mess of trapped baby turtles.

A green sea turtle swims off the coast of Florida. Photo by Jim Abernethy

A green sea turtle swims off the coast of Florida. Photo by Jim Abernethy

Armouring the coast is another option. Physical structures, like seawalls or rocky riprap, can block the oncoming waves, but any sand on the sea side of the armoring would wash away, leaving none for sea turtles or other organisms.

Florida’s coasts have another option in the form of “managed retreat”. In this scenario, people would vacate coastal areas, and construction crews would rip up man-made structures like roads, businesses and houses. With beaches being no longer constricted by hardened shorelines, they can move as waters elevate. This choice would obviously be less popular for Florida’s ever growing coastal population, Reece said. The state added more than 7 million people to its shorelines over the last two decades, which is second to only California in terms of coastal growth. Last autumn, Reuters reported that of 3,302 applications to build residential structures on Florida beaches since Jan. 1, 2000, only 114 have been denied permits.

“We must allow our beaches to move, but that is going to be really hard to do culturally and socially,” Doc said

As Doc and Reece talk about this grave future, their exuberance provides welcome counterweight. Reece’s enthusiasm is apparent as he walks down the beach. He casually lists off plant species when he passes a dune — “look, there’s some sea grape” — and you crane your neck to observe. One of his undergraduate students — senior Erika Schumacher — drove two hours from Orlando to check out the refuge with us. Her trip wasn’t for class credit, since school was still out. She merely came to observe.

Kate Mansfield, director of the UCF Marine Turtle Research Group (right), reviews the plans for a nighttime search for nesting sea turtles at Archie Carr National Wildlife Refuge in Melbourne Beach, Florida. Photo by Mike Fritz

Kate Mansfield, director of the UCF Marine Turtle Research Group (right), reviews the plans for nighttime search for nesting sea turtles at Archie Carr National Wildlife Refuge in Melbourne Beach, Florida. Photo by Mike Fritz

A pair of loggerhead hatchlings at the University of Central Florida Marine Turtle Research station in Melbourne Beach, Florida. Most mornings, the researchers collect any stragglers left behind in nests and then release them at night when fewer predators are active. Photo by Mike Fritz

A pair of loggerhead hatchlings at the University of Central Florida Marine Turtle Research station in Melbourne Beach, Florida. Most mornings, the researchers collect any stragglers left behind in nests and then release them at night when fewer predators are active. Photo by Mike Fritz

Erika is part of collective of students who recently led a petition to save Reece’s job. Like so many small colleges across the U.S., Valdosta State is facing lower enrollment, and the school is cutting the youngest faculty to balance the budget. Reece is facing the axe, even though his research grants are scheduled to bring more than $250,000 over the next two years.

Later that evening, Reece took us to meet Kate Mansfield, who took over directorship of the UCF Marine Turtle Research Group in 2013 when Doc stepped down. During the summer, a dozen researchers – a pack of undergrad and graduate students — live at a beach house about half a mile behind the refuge’s dune. Inside, it feels like half lab, half summer camp. The students sit around a square coffee table playing cards or chat on the screened-in balcony in the back. Two undergrads — Connor Carrell and Cody Sparaco — kill time by passing around a drawing notebook of sketches.

Each night around 9 pm, two of the researchers hop onto ATVs parked in the driveway. Their mission is to drive along the beach and spot mother turtles as they come on shore to nest. During peak nesting, 600 moms might hit the beach in one night. If the scouts spot one, then they will radio their location to Brazilian graduate student Gustavo Stahelin or another team leader at the base, and the rest of the scientists will head to the site. After a mom finishes laying, they’ll conduct health assessments and potentially tag the turtle so they can keep tabs on her nesting patterns.

So there we stood with a mother loggerhead.

“She has just finished clearing out a body pit, then she takes her rear flippers and she digs out an egg chamber, Mansfield said, narrating the turtle’s movements. “Once she gets all the way down to the bottom of where she can reach with her rear flippers, she kind of creates this lightbulb shape for the egg chamber.”

Nearby, students crowded around a bucket. Inside the bucket were two hatchlings that had been found on the beach earlier that day.

“If we have any stragglers left over in the nests, we will bring them back into a dark closet. Keep them in a quiet spot during the daytime. And then release them at night after dark, when the visual predators are not as active,” Mansfield said.

As the little ones scuttled toward the beach’s edge, I considered the survival of this beach. Will these hatchlings return one day to this shore expecting warm sand and find instead a hardened bluff or a concrete sea wall?

The mother loggerhead began crawling back to sea, her nest fully concealed. She moved like an human infant, front left flipper, rear right, front right, rear left. In the still-soft sand, her staggered shuffle left an imprint like bulldozer tracks.

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