Damaging high tides have cut into a record sea turtle nesting season for South Carolina.
Volunteers up and down the coast are still collecting season-end data on the nests, which will be finalized at the end of next month. But on two islands at the Tom Yawkey Wildlife Center, which got a perilously close pass from Hurricane Dorian last month, that storm and a slew of higher-than-normal king tides wreaked havoc, said Charlotte Hope, a biologist with the S.C. Department of Natural Resources' sea turtle program.
South Island lost 42 nests to Dorian, or 7 percent of the total laid.
Sand Island lost 38 nests, almost a third of the total there.
At Cape Romain National Wildlife Refuge, almost all of the nest losses on Cape Island and Lighthouse Island behind it have been due to tides or storms, according to collected data. Nests there have had about an 85 percent success rate, a 10-point dip from the year before.
Jerry Tupacz with the U.S. Fish and Wildlife Service said there were about 400 nests in place before Dorian, though workers at the refuge still don't know how many were flooded. The tides that came in shortly before the storm seem to have packed a bigger punch.
A colleague recently inventoried a row of seven nests on Lighthouse Island, and they "showed virtually no development," Tupacz said. "They probably got hit by the high tide shortly after they were laid."
Yawkey and Cape Romain are some of the most important nesting habitat in the state for the loggerhead sea turtle, a 3-foot, 300-pound emblem of marine conservation efforts along the Palmetto State's shores. While Dorian scraped past Charleston at a far enough distance that the city was spared its worst winds and tides, its eye was virtually atop Cape Romain and Yawkey.
This year had been shaping up as a record-smashing year for sea turtles, with almost 8,800 nests laid across the state, a number that surpasses data for at least the past decade, according to DNR. While loggerheads lay the vast majority of South Carolina's nests, a handful of smaller green turtles and one kemp's ridley also laid nests this year.
The laying season stretches from May to August, with volunteer groups up and down the coast marking where nests have been laid so beachgoers avoid them. In some cases, volunteers relocated nests entirely. The last hatchlings usually emerge by October.
It will not be clear until late November how well all of those nests fared.
A single storm doesn't always spell disaster, Hope said. A more pernicious problem this year was several rounds of king tides, or the highest of high tides, which occur based on the phase of the moon, the direction of wind coming off the water, or faraway storms kicking up swells in the Atlantic Ocean.
A record for the high tides was set in Charleston this year.
If a nest is covered by ocean waters only once, most of its eggs can survive. But continuous washovers can suffocate the eggs, or completely erode the sand they're embedded in.
Mary Pringle, of the volunteer Island Turtle Team, said her group regularly relocated nests that mother turtles lay near the tide line on Sullivan's Island and Isle of Palms. Most of the losses there this year came from predators, but one nest that wasn't moved did have groundwater infiltrate its egg chamber, she said; some eggs hatched but the success rate was much lower.
The water from a single washover also help lower the temperature of the nest, Hope said, which might help restore a natural balance of male and female hatchlings. The gender of hatched loggerheads depends on a narrow, 5-degree swing in incubation temperatures, and increasing heat due to climate change is making many nests mostly female, a destabilizing mix for the species.
Another danger for turtles as average global temperatures rise is a higher sea level, which eats away at sandy nesting habitat or pushes nests closer to grassy areas, where predators like raccoons may lurk.
A study from earlier this year showed that South Carolina and much of the Southeast faces a high risk of eroding beach habitat in the coming years, pushing to the brink not only sea turtles, but other nesting species, like shore birds.
In the case of Cape Romain, workers do their best to relocate endangered nests, but on hot summer days with little staff, some are inevitably left behind, Tupacz said.
"I just have to make that ugly decision sometimes," he said.