Endangered Turtle Population under Threat as Pollution may Lead to Excess of Females Being Born
Published:10 Jan.2024    Source:Griffith University

A Griffith-led study on the influence of pollution on the sex ratio of clutches of green sea turtles has found that it may compound the female-biasing influence of rising global temperatures. Published in Frontiers in Marine Science, the researchers concluded that exposure to heavy metals cadmium and antimony and certain organic contaminants, accumulated by the mother and transferred to her eggs, may cause embryos to be feminized in green sea turtles (Chelonia mydas), a species already at risk of extinction from a current lack of male hatchlings.

Green sea turtles are listed as endangered on the IUCN Red List of Threatened Species, threatened with risk of extinction due to poaching, collisions with boats, habitat destruction, and accidental capture in fishing gear. But they also face another more insidious threat linked to climate change. Sea turtles' embryos developing in their eggs have temperature-dependent sex determination, which means that more and more develop into females as temperatures keep rising. In the northern part of the Great Barrier Reef off Australia, hundreds of females are born for every male.
From these results, it is concluded that these contaminants mimic the function of the hormone estrogen, and tend to redirect developmental pathways towards females. As the sex ratio gets closer to 100% females, it gets harder and 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. Determining which specific compounds can change the hatchling sex ratios is important for developing strategies to prevent pollutants from further feminizing sea turtle populations. Since most heavy metals come from human activity such as mining, runoff, and pollution from general urban waste, the best way forward is to used science-based long-term strategies to reduce the amount of pollutants going into our oceans.