Even very low levels of pesticide exposure can affect fish for generations

Susan Brander, an associate professor and environmental ecologist at Oregon State University’s Hatfield Marine Science Center, said the findings are a concern not just for fish, but for all vertebrates that commonly use fish. Insects are affected by pesticides – including humans.

“This exposure is happening not just to these fish, but to all aquatic life in areas that flow through human-populated areas,” Brander said. “It’s safe to say that we’re seeing effects at the population level if fish that have been exposed for a few days as embryos and larvae are then producing offspring that are developmentally impaired, or males that are which are not able to produce more sperm.”

Climate change is also expanding the geographic range of many insect species, resulting in increased use of pesticides in both agricultural and residential settings, and the potential for more organisms to be exposed to harmful chemicals. is increasing.

The study, published in the journal Environmental Science and Technology, Inland silversides are used as a model fish species common in North American estuaries and marine waterways, with a particular focus on San Francisco Bay and the Sacramento-Joaquin Delta. OSU researchers chose three commonly used pyrethroid insecticides (bifenthrin, cyfluthrin and cyhalothrin) because of their high neurotoxicity and persistent presence in Bay Delta waters. These pesticides are also widely used and detected throughout the country.

For the experiment, the researchers exposed silverside embryos to various pesticides for 96 hours, at a concentration of 1 nanogram of pesticide per liter of water. That’s about a teaspoon of pesticide in an Olympic-sized swimming pool, Brander said.

After 96 hours, the fish larvae were placed in clean water and reared until they were five weeks after hatching. They are then kept in large tanks until they reach reproductive maturity at about eight months of age. At that time, the researchers gave birth to adult fish and collected their offspring for rearing in clean water. Behavioral responses were measured in larval parents as well as larval offspring.

The researchers found that the fish that were actually exposed to the pesticides exhibited hypoactive behavior, or reduced activity, at the larval stage, causing them to not search for food as well as the control group. , if they were in the forest. In contrast, the second generation of fish – the generation that was never exposed to the pesticide, except for their parents – exhibited highly active behavior, swam more and worked harder than the controls. The researchers speculate that this was a compensatory response to the hypoactive behavior of the previous generation.

Tests also found that adult male fish exposed to bifenthrin and cyhalothrin caused larvae to have smaller gonads than the control group, while second-generation fecundity increased.

While much research has focused on zebrafish as a model for human health, Brander says many fish species share a large proportion of their genes with humans, and thus models for predicting this. can be used as a measure of how humans may react to a chemical.

“This study is another demonstration of how exposure to these chemicals early in life can affect fish for months and, in the case of humans, potentially for years,” Brander said. “We can potentially use this as a model for how human babies or humans in utero might respond to these chemicals — fish use the same hormone receptors as we do; the same steroids. So Something that interferes with reproduction in fish is likely to have the same effect on humans.”

Brander said the results suggest the fish were able to adapt to exposure in some ways, but may be overcompensating, and such changes cost success in other biological processes such as growth or hunting. But can come.

“In terms of environmental regulation, if we were to impose strict controls because of studies like this, it would take a few species of fish — or whatever organism — to fully recover,” he said. In being Yab,” he said.

The study’s lead author was OSU doctoral student Sarah Hutton, who graduated last year and now works in environmental consulting. Other co-authors included Samrin Siddiqui, Emily Pedersen and Christopher Mark Graf at Oregon State. Amelie Segara and Richard Conan at the University of California, Davis; and Michelle Hladik at the US Geological Survey in California. The study was funded by the Delta Stewardship Council in California.