MIAMI (CBSMiami/AP) — Florida’s great egrets are having a bit of trouble these days getting in the mood to mate thanks to environmental toxins.

A University of Florida study has found that eating bad fish, contaminated with increased levels of mercury, is turning egrets off from sex.

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Using more than 20 years of biological and environmental data, the UF researchers found that mercury exposure led to a 50% reduction in the propensity of great egrets to initiate breeding in the Florida Everglades, meaning the heavy metal is affecting their reproduction process much earlier than previously thought. The study also noted the full effects of mercury exposure among wading birds may be “systematically underestimated.”

The study reported heavy metals and other contaminants can disrupt hormones, which can then impact a desire to breed.

According to the U.S. Environmental Protection Agency, most mercury pollution is emitted during the burning of fossil fuels and other human activity. This mercury floats through the atmosphere before settling on a surface, like water, where it can undergo a process called methylation, producing methylmercury, a highly toxic form that builds up in fish, shellfish and animals that eat fish, in a process known as bioaccumulation. Methylmercury is more easily absorbed by animals, and because it can stay in tissues for many months, it can move up the food chain and accumulate in predators like great egrets.

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Most human exposure to mercury is from eating fish and shellfish contaminated with methylmercury.

“This study suggests that there are a lot of birds that are just sitting out the breeding season. It’s not that they are starting and not successfully finishing; they aren’t even attempting to breed,” said Peter Frederick, one of the study’s co-authors. “And when you don’t breed, you don’t produce any chicks at all.”

The study is published in the journal “Environmental Science & Technology.”

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