Sex and Sea Turtles: Climate Change, Sea Level Rise Impacts
The shift in climate is shifting turtles as well, because as the temperature of their nests change so do their reproduction patterns. Warmer conditions produce females and cooler conditions produce males.
The nesting beaches along Florida鈥檚 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.
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鈥檛 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 91社区 have just published the results of a four-year study in the journal , on the effects of turtle nest temperatures and sand temperatures and on hatchling sex.
鈥淭he shift in our climate is shifting turtles as well, because as the temperature of their nests change so do their reproduction patterns,鈥 said Jeanette Wyneken, Ph.D., professor of biological sciences in 91社区鈥檚 Charles E. Schmidt College of Science. 鈥淭he nesting beaches along Florida鈥檚 coast are important, because they produce the majority of the loggerhead hatchlings entering the northwestern Atlantic Ocean.鈥
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鈥檛 produced because of climate changes, then this will result in a dire problem for this species.
鈥淚f climatic changes continue to force the sex ratio bias of loggerheads to even greater extremes, we are going to lose the diversity of sea turtles as well as their overall ability to reproduce effectively. Sex ratios are already strongly female biased,鈥 said Wyneken. 鈥淭hat鈥檚 why it鈥檚 critical to understand how environmental factors, specifically temperature and rainfall, influence hatchling sex ratios.鈥
Wyneken and her team documented rainfall and sand temperature relationships as well as rainfall, nest temperatures and hatchling sex ratios at a loggerhead turtle 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. 聽
Nest temperature profiles were synchronized with rainfall data from weather services to identify relationships with hatchling sex ratios. The sex of each turtle was verified laparoscopically to provide empirical measures of sex ratios for the nest and the nesting beach.
鈥淭he majority of hatchlings in the sampling were female, suggesting that across the four seasons most nest temperatures were not sufficiently cool to produce males,鈥 said Wyneken. 鈥淗owever, in the early portion of the nesting and in wet years, nest temperatures were cooler, and significantly more males hatched.鈥
The work was supported, in part by the National Save the Sea Turtle Foundation, Save our Seas Foundation and donations to the Nelligan Sea Turtle Support Fund.
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