Endangered by Chemicals: Pollutants Acting as Female Hormones Affect Green Sea Turtle Population

A recent study led by Griffith University has found that pollution may compound the female-biasing influence of rising global temperatures on the sex ratio of clutches of green sea turtles.

The research suggests that exposure to heavy metals such as cadmium and antimony, as well as certain organic contaminants that accumulate in the mother and are transferred to her eggs, may cause embryos to be feminized in green sea turtles, a species that is already at risk of extinction due to a lack of male hatchlings.

Dr Arthur Barraza, a researcher at the Australian Rivers Institute at Griffith University, explained that green sea turtles are listed as endangered on the IUCN Red List of Threatened Species due to various factors, including habitat destruction, poaching, and accidental capture in fishing gear.

However, they also face the threat of climate change, which has a temperature-dependent sex determination mechanism in sea turtle embryos, resulting in more females as temperatures continue to rise.

The study was conducted at a long-term monitoring site on Heron Island, a small coral sand cay in the southern Great Barrier Reef, where between 200 and 1,800 females come to nest every year.

The sex ratio at the Heron Island study site is currently more balanced than nearer the equator, with two to three females hatching for every male.

The research highlights the need for continued efforts to mitigate the impact of pollution and climate change on sea turtle populations.

A study conducted as part of WWF-Australia’s Turtle Cooling Project has found that pollution may compound the female-biasing influence of rising global temperatures on the sex ratio of green sea turtle hatchlings.

The study collected 17 clutches of eggs and reburied them next to probes recording the temperature every hour inside the nest and at the beach surface.

When the hatchlings emerged, their sex was determined, and levels of 18 metals and organic contaminants were measured.

The research found that contaminants such as antimony and cadmium, which act as xenoestrogens, increase the female bias within the nest.

As the sex ratio gets closer to 100% females, it becomes harder for adult female turtles to find a mate, which is particularly important in the face of climate change already making nesting beaches warmer and more female-biased.

The study highlights the need for long-term strategies to reduce pollutants going into the oceans to protect sea turtle populations.

How Do Sea Turtles Breathe?

Sea turtles breathe air through their external nares, which are like the nostrils we have to breathe air.

They can contract and extend their neck easily to get air from the surface without needing to get out of the water.

When sea turtles breathe in the air through the nares, the air travels to the trachea, which is long and flexible due to the shape of the neck.

The trachea reaches near the turtle’s heart and then divides into two parts called bronchi, through which oxygen is delivered to the lungs.

Sea turtles have large lungs that help to store more oxygen, allowing them to stay underwater for longer periods.

However, unlike humans, sea turtles do not have a separate rib cage. Instead, their rib cage is attached to their shell, and they have muscles inside the shell above the lungs on the rib cage that expand and contract like a regular rib cage to breathe air in and out of their lungs.

These muscles help turtles to breathe easily, and the lung pressure alters when the turtles move their flippers and neck, filling the lungs with air. Learn more here, Do Sea Turtles Need Air?

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