Pollutant Turns Fish into Poorer Parents and Fiercer Rivals

Topic: Environment

Researchers found that a common pollutant in water turned male fish into worse fathers and more aggressive rivals. The study was conducted on an entire lake ecosystem, not just in a lab.

A team of researchers has discovered that a common wastewater pollutant called ethinylestradiol (EE2) can have surprising effects on the behavior of male fathead minnows. EE2 is a synthetic estrogen used in oral contraceptives and other hormone therapies.

While laboratory studies suggested that exposure to EE2 would reduce aggression in male fish, researchers studying an entire lake ecosystem found the opposite. They observed more fish around active nests, increasing competition and causing nesting males to spend more time defending territories and eggs.

To better understand the hormone's effects in a natural setting, researchers conducted a whole-lake experiment, monitoring male fathead minnows before, during and after a three-year period during which trace amounts of EE2 were added to an experimental lake. They compared the fish with populations living in nearby lakes that were not exposed.

The researchers found that EE2 changed the social dynamics of the fish population. Male fathead minnows normally establish territories, court females and guard the eggs laid in their nests. During the exposure period, competition around active nests increased. The added rivalry, combined with reduced parental care and fewer eggs in nests, likely contributed to the population collapse observed during the experiment.

Why It Matters

This study shows how pollution can affect not just individual animals but also the entire ecosystem. Understanding these effects is crucial for protecting wildlife populations and our environment.

Key Facts

• Researchers studied the effects of ethinylestradiol (EE2) on male fathead minnows in a lake ecosystem over three years.
• The study found that EE2 increased competition among fish, leading to reduced parental care and population collapse.
• Laboratory studies had previously suggested that EE2 would reduce aggression in male fish, but the whole-lake experiment showed the opposite effect.
• EE2 is a synthetic estrogen used in oral contraceptives and other hormone therapies.
• The study was conducted by researchers from McMaster University, the Swedish University of Agricultural Sciences, and Fisheries and Oceans Canada.

Key Terms

Ethinylestradiol (EE2)

A synthetic estrogen used in oral contraceptives and other hormone therapies.

Implications

This study shows how pollution can affect not just individual animals but also the entire ecosystem. Understanding these effects is crucial for protecting wildlife populations and our environment.