Sea-turtle research on heat's effect on eggs may aid conservation

Joe Burbank, Orlando Sentinel / Sep 02, 2012)

By Ludmilla Lelis, Orlando Sentine
As people flock to the beach on Labor Day, sea turtles are emerging from their dune nests in what could be record numbers.

Canaveral National Seashore and neighboring beaches in Central Florida are reporting record numbers of loggerhead sea-turtle nests, a promising change from a decade-long drop.

But now a new threat is looming: rising temperatures. Summer temperatures are slowly increasing at Canaveral. And with climate-change scenarios projecting even hotter summers, there's increasing concern that it might get so hot that the eggs may literally fry.
This could mean trouble especially for the male of the species, which is already at a disadvantage in Florida. Sea-turtle biologists have long used the adage "hot mamas, cool dads" as a reminder that loggerhead sea turtles become male or female based on the temperature when their eggs incubate — higher temperatures make them females.

With the prospect of even hotter weather as a backdrop, the interplay between temperatures and sea-turtle eggs is the basis for a study by University of Central Florida graduate student Monette Auman, who is tracking nest temperatures and hatching success of some loggerhead sea-turtle nests at Canaveral National Seashore.

"It's an interesting subject to discuss because there are questions like, 'What does an overabundance of females mean to the population?" Auman said. "And what happens if rising temperatures put sea turtles in a more precarious situation?"

From 2001 to 2011, average temperatures at Canaveral were 1.3 degrees Fahrenheit higher than they were from 1961 to 1990, according to a new study released by two environmental groups, the Rocky Mountain Climate Organization and the Natural Resources Defense Council.

Climate-change scenarios suggest that average temperatures could continue to increase an additional 1.8 to 4 degrees by 2060, the report said.

Loggerhead sea turtles are protected under federal law as a threatened species, and Florida beaches are home to 90 percent of the nation's loggerhead nests, making the state's shoreline crucial to the species' survival. The marine-turtle nests are closely tracked, and regulations protect them from human interference.

In recent years, scientists have been concerned that the loggerheads may be in trouble. Though nest counts steadily increased during the 1990s, those counts plummeted 40 percent to record lows in 2007.

This summer could be the turtle's comeback season, though. Archie Carr National Wildlife Refuge, straddling Brevard and Indian River counties, is one of the world's most important nesting beaches and has had 18,425 nests to date. Volusia County has had a record-setting 902 loggerhead sea-turtle nests. Canaveral National Seashore has topped its prior record with more than 5,700 nests.

"We saw almost a 40 percent decline in loggerhead nesting in Florida [from 1999 to 2007], and it seemed that something was seriously wrong with the population," said David Godfrey, executive director of the nonprofit Sea Turtle Conservancy. "Yet nesting is skyrocketing this year, and it reminds you as a turtle conservationist that we don't know everything that is affecting turtle behavior or nesting patterns."

Scientists have long known that temperature can have a strong effect on the coldblooded reptiles. A winter freeze can shock young turtles into paralysis, as happened to thousands of young green sea turtles in 2010.

On the flip side, heat can speed up egg incubation, make all the turtle eggs turn female and, at the extreme, cause the eggs to fail. Some studies estimate that 80 percent to 99 percent of Florida hatchlings may be female, while the nests at beaches in Georgia and the Carolinas tend to produce more males.

Rising temperatures, and other effects of climate change, pose a great threat to the sea turtle and its habitat at Canaveral, the study by the environmental groups says.

"If the trend continues, we'll have more females and fewer males, and at some point, we may have nothing but females," said Stephen Saunders, president of the Rocky Mountain organization.

Auman hopes to take the temperature research further. Through her work at Canaveral, she aims to get a closer look at temperature and its effects on the nests. With the data collected from her temperature probe, she hopes to find correlations between the temperature readings and the hatching success.

The research could offer scientists information that could help Florida wildlife officials help conserve the species, said Blair Witherington, a research scientist with the Florida Fish and Wildlife Research Institute, the research arm of the Florida Fish and Wildlife Conservation Commission.

"We can forecast what populations are likely to look like given the climate regime we're heading into," Witherington said. "On a warmer beach, with more females, what will that population be like?"


Source: http://articles.orlandosentinel.com/2012-09-02/news/os-sea-turtles-hot-sand-20120827_1_loggerhead-nests-nest-counts-loggerhead-sea-turtle-nests

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