ST. PAUL, Minn. (FOX 9) – Zebra mussels significantly modify the ecosystems of Minnesota lakes, according to a study that links invasive species to higher mercury levels in fish.

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What we know

Researchers gathered data from 21 Minnesota lakes to examine the impact of zebra mussels on the aquatic ecosystem.

They found that fish from lakes infested with invasive zebra mussels had much higher concentrations of mercury – a potent neurotoxin that threatens both aquatic life and human health.

Walleye from lakes infested with zebra mussels have been shown to contain 72% higher amounts of mercury than lakes without zebra mussels.

The study also states that “medium-sized walleyes were more than twice as likely to exceed human health-related mercury thresholds.”

The Minnesota Department of Health’s mercury concentration threshold is 0.22 parts per million, and the study indicates that walleye in zebra mussel-infested lakes reached this concentration at a much smaller size, more precisely 14 inches instead of 18 inches.

Meanwhile, yellow perch had a 157% higher mercury concentration in lakes with zebra mussels, with medium-sized yellow perch having a 50 times higher risk of exceeding the mercury threshold considered acceptable for human health.

The study also found that walleye and perch are more reliant on nearshore feeding habits due to the zebra mussel invasion.

The study was carried out by researchers from University of Minnesota College of Food, Agricultural and Natural Resources Sciences, Minnesota Aquatic Invasive Species Research Center and US Geological Survey. It was also published in the peer-reviewed journal Science of the Total Environment.

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What they say

Gretchen Hansen, associate professor in the Department of Fisheries, Wildlife and Conservation Biology and lead author of the study, said: “We were surprised to see such a strong effect of zebra mussels on mercury concentrations in fish tissues, and we look forward to conducting further research to understand exactly the mechanism behind these patterns.