Increases in the temperature of the northern part of the Great Barrier Reef brought about by climate change have had a profound effect on sexual diversity amongst the green sea turtles in this region. We have a very good idea why this is happening, and once again it is humanity's fault.
Increasing temperatures in Queenslands north, linked to climate change, are being blamed because the incubation temperature of eggs determines the sex of turtles with a warmer nest resulting in more females.
Increased temperatures has caused many sea turtles to become female. Using a combination of endocrinology and genetic tests, researchers identified the turtles sex and nesting origin.
A study published today in the journal Current Biology - led by the National Oceanic and Atmospheric Administration (NOAA) in the U.S. and in conjunction with scientists from Australia - found the group of turtles had primarily produced females for two decades, because of increasing temperatures.
The "pivotal temperature" that creates a 50/50 split of male and female can be passed down from parent to offspring.
In the past, a particularly hot or cold year might have produced more of one sex than the other, but for a species that doesn't mate until at least the age of 25, this didn't matter much as long as it evened out over several years.
This is a Shakespearian Sonnet, inspired by recent research which has shown that climate change has caused populations of green sea turtles from the northern Great Barrier Reef to be almost entirely female.
Turtles from the cooler southern GBR nesting beaches showed a more moderate female sex bias (65%69% female). The mid-reef region has nearly no hatcheries. Additionally, 99.8 percent of "young adult" and 86.8 percent of adult-sized turtles that hatched from the same beaches were female.
If we don't actively combat climate change, we may lose green sea turtles forever.
Clownfish are all born male, with most dominant male of the group will become female.
"This is extreme ― like capital letters extreme, exclamation point extreme", Camryn Allen, marine biologist and co-author of the study, . The turtle researchers warned that without proper management, we could see these critical green sea turtle populations go extinct within a few decades.
But the only way to find that out is to do the same study for different turtle populations, which sea turtle biologist Kate Mansfield says is necessary to protect conservation efforts for the animal.
"Unfortunately in this case, that may be one thing they do not have", she added.
Allen said the government of Australia has started to take steps toward helping sea turtles, such as funding the Raine Island Recovery Project to study and support the local turtle population.
They captured 411 foraging turtles, one at a time, drawing blood to measure gender hormones and taking skin samples for DNA.
The group conducted its research over 16 days in July 2014, plying small boats around the Howick Group of islands in the north Great Barrier Reef - "an absolutely magical place", according to Jensen.
The Queensland Department of Environment has been experimenting with shade cloths for loggerhead turtles in southern parts of the state.
When the researchers combined their data with temperature data, they found the northern population has been producing primarily females for over two decades.
Indeed, the study performed by Michael Jensen of the National Oceanic and Atmospheric Administration in La Jolla and colleagues reveals that male turtles from the northern Great Barrier Reef are becoming increasingly rare.
The results are correlative rather than definitive, says Jensen, but are nonetheless "worrying".