Too many green turtles being born female due to rising sea temperatures

15 Jan 2018

Image: divedog/Shutterstock

In another example of the ecological damage caused by rising sea temperatures, the sex diversity of green turtles in the Great Barrier Reef has been thrown out of whack.

As if the mass bleaching of coral in the Great Barrier Reef wasn’t enough of a problem, new research on the local green turtle population has revealed some startling and worrying facts.

According to the World Wildlife Fund, rising sea temperatures in the region has resulted in the species’ population – almost 200,000 – in the northern area of the reef being almost completely female.

During the incubation period of the turtle eggs, the sex is dependent on the warmth of the mother’s nest – meaning the warmer the nest, the more females are born.

As sea temperatures increase, the creature’s sex diversity has been thrown completely out of whack, with findings showing that among the green turtles found in nesting beaches, 86.8pc were female.

This “extreme female bias” has been occurring over the past 20 years and is remarkably different to the southern reef, where a more moderate female sex bias of between 65pc and 69pc was found.

 ‘Should ring alarm bells’

The study was led by Dr Michael Jensen from the US’s National Oceanic and Atmospheric Administration. It involved catching green turtles at the Howick Group of islands where both northern and southern green turtle populations forage in the Great Barrier Reef.

Determining the sex of the turtles was then achieved using a combination of endocrinology and genetic tests.

The Great Barrier Reef is home to more than 1,500 species of fish, seven species of threatened marine turtles and more than 30 species of marine mammals.

Speaking of the findings, WWF Australia CEO Dermot O’Gorman said: “Finding that there are next to no males among young northern green turtles should ring alarm bells, but all is not lost for this important population.”

Earlier this month, it was revealed that coral bleaching has affected so much of the world’s existing reefs that some areas may be bleached beyond repair.

The study found that the time between bleaching events in coral reefs has dropped dramatically by a factor of five in the past 30 to 40 years, bringing it to an unsustainable level.

Colm Gorey was a senior journalist with Silicon Republic