Sex and sea turtles: New study reveals impact of climate change, sea level rise

October 15, 2015, Florida Atlantic University
Loggerhead turtles are already fighting an uphill battle since roughly one in 2,500 to 7,000 sea turtles make it to adulthood. Credit: Florida Atlantic University

Marine turtles deposit their eggs in underground nests where they develop unattended and without parental care. Incubation temperature varies with environmental conditions, including rainfall, sun, shade and sand type, and affects developmental rates, hatch and emergence success, and embryonic sex. Although the loggerhead turtle has been around for more than 60 million years, drought, heavy rainfalls and climatic changes are impacting hatchling sex ratios and influencing future reproduction. Because sea turtles don't have an X or Y chromosome, their sex is defined during development by the incubation environment. Warmer conditions produce females and cooler conditions produce males.

Researchers from Florida Atlantic University have just published the results of a four-year study in the journal Endangered Species Research, on the effects of turtle nest temperatures and temperatures and on hatchling sex.

"The shift in our climate is shifting turtles as well, because as the temperature of their nests change so do their reproduction patterns," said Jeanette Wyneken, Ph.D., professor of biological sciences in FAU's Charles E. Schmidt College of Science. "The nesting beaches along Florida's coast are important, because they produce the majority of the loggerhead hatchlings entering the northwestern Atlantic Ocean."

Loggerhead turtles are already fighting an uphill battle since roughly one in 2,500 to 7,000 sea turtles make it to adulthood. The typical loggerhead produces about 105 eggs per nesting season and would have to nest for more than 10 nesting seasons over the span of 20 to 30 years just to replace herself and possibly one mate. And, if enough males aren't produced because of climate changes, then this will result in a dire problem for this species.

"If climatic changes continue to force the sex ratio bias of loggerheads to even greater extremes, we are going to lose the diversity of as well as their overall ability to reproduce effectively. Sex ratios are already strongly female biased," said Wyneken. "That's why it's critical to understand how environmental factors, specifically temperature and , influence hatchling sex ratios."

The majority of hatchlings in the sampling were female, suggesting that across the four seasons most nest temperatures were not sufficiently cool to produce males. Credit: Florida Atlantic University

Wyneken and her team documented rainfall and sand temperature relationships as well as rainfall, nest temperatures and hatchling sex ratios at a nesting beach in Boca Raton, located in southeast Florida. Nesting season, which runs from April through October, were sampled across 2010 and 2013. The researchers used temperature dataloggers in the sand at three locations and buried them at three different depths to create temperature profiles of the sand column above the level that would directly influence eggs. The rainfall data were graphed in temporal synchrony with sand temperature for each depth.

Nest temperatures were recorded throughout incubation. Rainfall data collected concurrently with sand temperatures at different depths showed that light rainfall affected only the surface sand; effects of the heaviest rainfall events tended to lower sand temperatures, however, the temperature fluctuations were very small once the moisture reached upper nest depths.

The nesting beaches along Florida's coast are important, because they produce the majority of the loggerhead hatchlings entering the northwestern Atlantic Ocean. Credit: Florida Atlantic University

Nest temperature profiles were synchronized with from weather services to identify relationships with hatchling sex ratios. The sex of each turtle was verified laparoscopically to provide empirical measures of for the nest and the nesting beach.

"The majority of hatchlings in the sampling were female, suggesting that across the four seasons most nest temperatures were not sufficiently cool to produce males," said Wyneken. "However, in the early portion of the nesting and in wet years, nest temperatures were cooler, and significantly more males hatched."

Explore further: Warmer beaches influence sex ratios of loggerhead hatchlings

Related Stories

Warmer beaches influence sex ratios of loggerhead hatchlings

October 22, 2013

While Dirk Hartog Island is the southernmost rookery for loggerhead turtles (Caretta caretta), UWA and Murdoch University biologists say climate change may ultimately lead to the species nesting successfully on beaches further ...

Baby sea turtles starved of oxygen by beach microbes

February 26, 2015

On a small stretch of beach at Ostional in Costa Rica, hundreds of thousands of sea turtles nest simultaneously in events known as arribadas. Because there are so many eggs in the sand, nesting females frequently dig up previously ...

Sea turtles set new nesting records in US

September 7, 2015

Sea turtle experts along the southeastern U.S. coast say new nesting numbers reinforce their belief that loggerhead sea turtles are making a comeback after 37 years of protection as a threatened species under the federal ...

For sea turtles, there's no place like magnetic home

January 15, 2015

Adult sea turtles find their way back to the beaches where they hatched by seeking out unique magnetic signatures along the coast, according to new evidence from the University of North Carolina at Chapel Hill.

Recommended for you

Understanding how to control 'jumping' genes

June 22, 2018

A team of Texas A&M University and Texas AgriLife Research scientists have made a new discovery of how a single protein, Serrate, plays dual roles in controlling jumping genes.

5 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

gkam
1 / 5 (2) Oct 15, 2015
No sweat. philstacy just referenced a paper which says there is no sea level rise, so the turtles must be making a joke on us.

How did they know to do that?
plasmasrevenge
1 / 5 (2) Oct 15, 2015
Perhaps the point of the research should be to ask the question of how the turtles survived through former changes in climate over those 60 million years. It seems to me that the point of this research is politicized by its refusal to ask that obvious, arguably more important question.
gkam
1 / 5 (2) Oct 15, 2015
Maybe they already know. Since you are not in their field, you will have to look it up.
barakn
3.7 / 5 (3) Oct 15, 2015
The usual easily debunked denier argument: climate has changed in the past, so nothing could possibly go wrong. The rate of change determines whether species can adapt quickly enough to keep up with the change. Do some research on mass extinctions before you open your trap again.
barakn
5 / 5 (1) Oct 16, 2015
Looks like Noumenon also needs a lesson on what a 'rate' is.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.