Waterborne toxic pollutants can affect fish for generations

The effects of some forms of chemical poisoning acquired from the environment can pass down three generations. At least in fish.

Small fish that get exposed even to low levels of synthetic endocrine-disrupting chemicals that have become common in many freshwater sources can end up passing on the genetic impacts of these chemicals to their offspring that were never directly exposed to the same chemicals, say researchers at Oregon State University in the United States.

This phenomenon can impact three generations of fish, which is equivalent to having grandparents that come in contact with pollutants in their environment passing the effects on to their grandchildren, the scientists explain in a study published in the journal Frontiers in Marine Science.

Endocrine disruptors mimic hormones in the body and can lead to adverse biological effects in aquatic and other animals by triggering changes in their development, behavior and fertility rates.

These chemicals are used in a myriad of household and industrial products, including flame retardants, food items, toys, cosmetics and pesticides. They often leach into water sources where they then accumulate. Even in small quantities they can have a marked impact. It has been shown previously that when fish are exposed to these chemicals in their environment their populations can end up suffering from altered sex ratios, lower fertility rates and various deformities.

In their own research the scientists in Oregon examined how the chemicals impacted generations of inland silversides (Menidia beryllina), a small fish native to estuaries in the eastern part of North America and the Gulf of Mexico where they feed largely on zooplankton. These little fish  are an important source of food for birds and predatory fish.

In an experiment the scientists exposed inland silversides to the equivalent of just a few drops of endocrine disruptors in an Olympic-size swimming pool, which is a relatively low concentration. They then set about studying three generations of fish for 21 months to see if the effects of the chemical passed from generation to generation.

To their surprise they found marked changes across three generations, even though only the first generation was exposed to the endocrine disruptors for a few weeks in early life. The growth and development of subsequent generations were also found to be affected. Needless to say, that is a disconcerting finding.

“It’s really important to understand how animals can deal with stress in the environment, particularly when we are introducing new stressors on a daily basis,” stresses Susanne Brander, an assistant professor and aquatic toxicologist at the university’s Department of Fisheries and Wildlife.

“Our research helps show what animals do to respond to these changes and how quickly they can respond to them. That’s going to help us understand our impact on the environment in the long run,” she adds.