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Reservoirs partly responsible for invasive lake species
Brittany Anas Boulder Daily Camera
A growing number of dams and man-made reservoirs is leading to a surge in unwelcome lake-water lurkers, such as zebra mussels and spiny water fleas, according to a new study led by the University of Colorado.

Impoundments create “stepping-stone habitats” for invasive species to sneak into natural lakes, ponds and waterways, where they disrupt the natural habitat.

The research team combined data on water chemistry, the distribution of five “nuisance invaders” and boating activity from the Great Lakes region for the study, according to Pieter Johnson, an assistant professor at CU and one of the lead authors.

Zebra mussels recently jumped to reservoirs in the West, including Colorado, Johnson said, leading to mandatory boat inspections at some landings. Other invaders are either already in Colorado — the rainbow smelt and water milfoil — or have a high probability of being introduced, such as the spiny water flea and rusty crayfish, Johnson said.

In Boulder, officials are looking to hire two inspectors this month to make sure zebra mussels don’t hitchhike on visitors’ boats and make their way into the Boulder Reservoir, disrupting the biodiversity, said reservoir manager Stacy Cole.

“The Division of Wildlife has been monitoring the reservoir, and there are no signs of the zebra mussels at this point,” she said.

To keep the invasive species out, the inspectors will look over all watercrafts — including boats, kayaks and windsurfers — and ask visitors to fill out a survey about other places they have taken their boats, Cole said. The initial inspections could take up to 40 minutes, she said.

Freshwater invaders can wreak havoc on natural ecosystems by competing with local fish populations, changing the water clarity and gunking up fishing gear and water-pumping equipment, according to the study.

“We believe impoundments may be functioning as ‘hubs’ for freshwater invaders, aiding their spread and establishment into natural water bodies,” said Johnson, a professor of ecology and evolutionary biology.

The study says free-flowing rivers leading to standing water may help spread the invasive species.

Researchers looked at data from 4,200 lakes and more than 1,000 impoundments —including man-made bodies of water such as cattle ponds and reservoirs — across Wisconsin and the Upper Peninsula of Michigan. The study showed non-indigenous species are up to 300 times more likely to occur in those impoundments than in natural lakes, increasing the invasion risks for natural lakes.

The results suggest that the benefits of building more reservoirs should be carefully balanced against the potential negative impacts, such as a spike in biological invasions, Johnson said.

Climate changes leading to an increased demand for water and flood control are expected to drive the construction of new reservoirs in many regions of the United States, including the Midwest, according to the study’s authors.

There are now more than 80,000 large dams and an additional 2.5 million smaller man-made bodies of water across the United States, Johnson said.

The study appears as the cover story in the September issue of Frontiers in Ecology and the Environment. Co-authors include Julian Olden of the University of Washington in Seattle and Jake Vander Zanden of the University of Wisconsin-Madison.

The study was funded in part by the National Science Foundation.