Pollution Has Unexpected Effect on Green Sea Turtles

Researchers say it's helping create too many females
By John Johnson,  Newser Staff
Posted Nov 27, 2023 11:48 AM CST
For Green Sea Turtles, a Big Problem: Too Many Girls
It's a safe bet that most of these green sea turtle hatchlings are female.   (Getty / atosan)

For male green sea turtles, it's the second part of a double whammy they could ill afford. A new study suggests that ocean pollution is contributing to a serious gender imbalance—way too many females are being born and way too few males, reports Science Alert. As the Washington Post explains, male green sea turtles already were in trouble because of a birthing quirk of the species: Nest temperature influences gender, and the warmer the sand is, the more females are produced. Given that global temperatures have been on the rise for years, that has put the male-to-female ratio out of whack, so much so that scientists say the turtles' very existence is at risk. Now comes this new study in Frontiers in Marine Science, adding to the problem.

Researchers took liver samples from hatchlings in the southern Great Barrier Reef and analyzed them for pollutants, such as the heavy metals cadmium and chromium, along with polychlorinated biphenyls, or PCBs. The higher the concentrations, the more likely the hatchlings were to be female, because the contaminants also influence gender, per a news release at Griffith University in Australia. Essentially, the contaminants "mimic the female sex hormone estrogen" inside the embryo, explains the Post, and that tilts the odds toward female births.

Adult females accumulate the pollutants in their bodies, where they're absorbed by the eggs they produce and can remain for years inside their offspring, say the researchers. The news is grim for a species that already has some colonies that are 99% female. But the researchers also voice hope for eventual improvement—provided we humans cooperate. "Since most heavy metals come from human activity such as mining, runoff, and pollution from general urban center waste, the best way forward is to [use] science-based long-term strategies to reduce the input of pollutants into our oceans," says Jason van de Merwe, a marine ecologist at Griffith and lead author on the study. (More sea turtles stories.)

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