Green Sea Turtles in the Great Barrier Reef Turn Female
Climate change has long been affecting the Great Barrier Reef, causing coral bleaching and harming many species of marine animals and plants. Now, almost all the sea turtles in the Great Barrier Reef turn females. Green sea turtles do not develop into females or males because of sex chromosomes. They are influenced by the temperatures outside the egg. The sex of the growing embryo depends on the temperatures that surround the egg.
Scientists have developed a new study, proving that this biological trick can endanger the future of green sea turtles as the planet gets warmer. Numerous sea turtle populations are affected by heat. The new study published in the journal Current Biology shows that the heat has such a great impact that most of these young reptiles are females.
David Owens is a professor emeritus at the College of Charleston. He was not part of the study, but he argues that this report represents one of the most crucial conservation papers of this decade. Most likely, it will green sea turtles from a few decades to a century to completely lose all the males in their populations.
Climate change affects green sea turtles
The environment in which the mother lays the egg dramatically influences the sex of a green sea turtle. Camryn Allen is a National Oceanic and Atmospheric Administration endocrinology researcher. She is also the co-author of the new study. She argues that these creatures have temperature-related sex determination. Hence, for them, is not like for the rest of the animals. It is not genetics, but the temperature which decides their sex.
At a pivot temperature, turtles hatch as both females and males. The pivot temperature represents 29.3 degrees Celsius. If the temperature drops a few degrees below this value than all the sea turtles will be born males. In case the temperatures rise, then all the sea turtles that hatch will be females. Michael Jensen is an NOAA marine biologist and the co-author of the study. He claims that a change of only a couple of degrees can trigger a transitional range from 100% males to 100% females.
The prime turtle nesting grounds are situated along the east coast of Australia, near the tip of the continent. Approximately 200,000 turtles lay their eggs on the beaches of Raine Island. Here takes place one of the largest green sea turtle gatherings. These marine creatures play a really important role in their ecosystems. They eat sea grass beds, and the nibbles of the turtles seem to keep plants healthy.
The area where the turtles feed is not inhabited by humans. The lands are pristine. However, many tiger sharks and dugongs pass by. Along the east coast of Australia, scientists have gathered 30 years of knowledge about this particular species. This area seems to be the perfect spot to analyze the population of green sea turtles.
Scientists used historical data regarding temperatures
When developing the study, researchers have collected turtles for several weeks. They released them immediately after taking some plasma samples. They argue that it is pretty difficult to differentiate young male turtles from females. There are no particular external features that could help them. In the past, scientists used to cut open young turtles to analyze their gonads.
However, researchers involved in the study do not want to have a negative impact on their population. The International Union for Conservation of Nature lists green sea turtles as an endangered species. Allen came up with a new technique to reveal the sex of the turtles via their hormones. In a California lab, scientists have analyzed the plasma samples.
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Allen says that they could not use genetic tests since these turtles do not have sex chromosomes like we do. Back in 2016, biologists have revealed the first turtle thermometer gene in snapping turtles. Even if not all the species of turtles depend on temperatures to establish their sex, snapping turtles are similar in this regard to green sea turtles. Scientists have also revealed that turtles which grow in colder conditions tend to grow larger.
Hence, if the larger turtles are males, it might benefit the entire species. Other studies have indicates that green sea turtles, as well as other reptiles which depend on temperatures, might change due to warmer climate. Owens says that many species of turtles around the world suffering right now because of a warmer climate. Some of the turtle species researchers had studied show 90% female populations.
Most green sea turtles that hatch are females
Raine Island seems to be a baby factory when it comes to green sea turtles. However, the study shows that the assembly-line only goes in one direction. Female turtle hatches after a female turtle. Hence, the study concluded that 99% of the young turtles are females. Furthermore, 87% of mature turtles are female. Hence, for every male turtle, there are about 116 female turtles.
Even if the entire population does not vanish tomorrow, in the long run, the entire species will disappear if temperatures continue to rise. As long as the high number of female turtles can find males to fertilize their eggs, the population might increase. These creatures do not need a 50:50 ratio of females to males. Jensen argues that only a few males can go a really long way.
Compared to female turtles, male turtles mare more frequently. Rory Telemeco is a biologist at California State University Fresno who studies the connection between reptile development and temperature. She argues that this discovery can have a wide range of “cascading consequences”.
Study authors used historical air and sea temperatures to estimate sand temperatures in the breeding grounds between 1960 and 2016. Researchers revealed that by the 1990s, the sand temperature estimates were higher than the pivot temperature. The main factor here is climate change.
One more time, climate change damages a species living near the Great Barrier Reef. The hot temperatures influence the sex of green sea turtles through their eggshell. Scientists have developed a new study which revealed that there are more female turtles which hatch compared to males. The sex of green sea turtles is not influenced by sex chromosomes, but by weather conditions. If temperatures continue to rise than this species will completely disappear.