Green sea turtles are one of the most amazing creatures on this planet. They travel the world on the currents of the ocean and return to their birthplace to give birth to the next generation of turtles.
Researchers studying the green sea turtles have recently discovered that the turtles that have hatched at the northern end of the Great Barrier Reef are missing a pivotal factor in their survival: the male species.
Many reptiles gender is not determined by chromosomes but rather the temperature at which the eggs are incubated. As climate science has grown, many have predicted that human-induced climate change could potentially cause a species to only produce one sex, eventually leading to to extinction.
With the recent finding on the northern end of the Great Barrier Reef, it appears that prediction has come true for at least the green sea turtles on the northern end of Queensland.
Sea turtles birth is determined by what is called temperature-dependent sex determination (TSD). When eggs hatch from sand that averaged 29ºC (84ºF) over the incubation period, they produce a 50-50 mix of males and females. Cooler temperatures mean more males, while warmer ones mean more females. As temperatures warm faster on the northern end of the reef, reptiles and coral alike are the ones with the most to risk.
The green sea turtle has always seen a the hatching’s gender vary based on a hot or cold year but due to the age at which they first give birth at, typically 25 years, they have always naturally balanced out the population. But with the never before seen staggering difference in gender hatching, global warming has many concerned about the future of the species and the health of the ecosystem. Green sea turtles play a pivotal role in the balance of the ecosystem including being one of the only species that eat jellyfish and control the population.
The southern end of the reef is still faring better as 65-69 percent of turtles are female and could actually improve breeding prospects compared to a 50-50 ratio in a species where some males mate with many females but the mid-reef region has almost no hatcheries. Among those born north of Cooktown, 99.1 percent of the juvenile turtles researchers examined were female, along with 86.8 percent of adults which causes concern the high level of concern.
Turtles from both ends of the reef feed in the same places, so researchers have used genetic analysis to classify where a turtle was born while establishing its sex. The same feeding grounds also had some turtles from New Caledonia and other Pacific islands, whose sex ratios were quite similar to those of turtles born at the southern end of the Great Barrier Reef.
Looking forward, researchers are performing experiments on shady beaches favored by the loggerhead turtles in the south. The idea is that the shaded areas could be extended to the green turtles, hopefully to rebuild a healthy population of male and female turtles.