We’ve known for years that the chemicals we pour down our drains and flush into our sewers often has a negative impact on the fish that live in our lakes and rivers. But a recent study of 50 different freshwater sites in Great Britain, undertaken by the University of Exeter, has shown that the impact of some of our waste products may be worse than expected.
The estrogens found in some birth control pills and plastics is actually causing some male fish to become intersex, meaning that they are starting to display both male and female physical characteristics. For example, their sperm counts have been greatly reduced, and some have even started producing eggs. These effects were found in roughly 20% of the male fish that were tested at the study sites.
The effects of these estrogens on fish go beyond altering their sex, though. Some of the estrogens found in plastics are even more dangerous in that they can damage the valves in their hearts. And the problems don’t end with just the affected fish themselves, since the offspring of these fish have proven to be more susceptible to these chemicals. This means that, even if the pollution stopped immediately, it could take several generations of fish for the effects of the chemicals to wear off.
It’s not just estrogens that are problematic, either. Other studies have shown that antidepressants that end up in the water are also causing problems. They are making some fish more social and less shy. This is problematic because it is changing the way some fish interact with predators. Since they are more social, they will sometimes swim right up to a predator instead of trying to hide. Of course, this results in increased death rates for these prey species.
This is not the first study to look at the effects of estrogen exposure on fish gender. Research conducted in the Potomac River in Washington, D.C., discovered that over 80% of male bass fish in the river had become intersex. Many of them had begun producing eggs. After being tested, they were found to be contaminated with hundreds of different chemicals.
Scientists hope to discover which specific chemicals are more likely to produce these changes in fish. Then, they intend to figure out a way to stop them from getting into the world’s freshwater ecosystems, or perhaps even find a way to mitigate their effects on the animals that live in the water. At a time when fish populations worldwide are declining due to habitat loss and climate change, researchers hope these studies will help them decide how best to protect them.