Biological invasions increasing due to freshwater impoundments
3 Sep 2008, 1317 Hrs

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Washington, September 3 (ANI): A new study, led by researchers at the University of Colorado at Boulder, US, has indicated that the growing number of dams and other impoundments is increasing the number of invasive species and the speed at which they spread, putting natural lakes at risk.

The research team combined data on water chemistry, the distribution of five "nuisance invaders" and boating activity from the Great Lakes region.

According to CU-Boulder Assistant Professor Pieter Johnson, co-lead author of the study, the results showed the increasing occurrence of such species in impoundments creates "stepping-stone habitats" for them into natural lakes, ponds and waterways in the region.

The researchers looked at invaders like the Eurasian zebra mussel, the Eurasian water plant known as watermilfoil, the Eurasian spiny water flea, the rusty crayfish and the rainbow smelt.

"Such freshwater invaders often have direct negative effects on lake ecosystems, including reduced fishing success, changes in water clarity and fouling of fishing gear and water-pumping equipment," Johnson said.

The study showed impoundments significantly reduced the average distance between "uninvaded" lakes and lakes inhabited by zebra mussels, increasing the number of natural lakes considered vulnerable to zebra mussel invasion by 50 percent.

Zebra mussels recently jumped to reservoirs in the West, including Colorado, leading to mandatory boat inspections at some landings, according to Johnson.

The other invaders are either already in Colorado - the rainbow smelt and water milfoil - or have a high probability of being introduced, like the spiny water flea and rusty crayfish, he added.

"We believe impoundments may be functioning as 'hubs' for freshwater invaders, aiding their spread and establishment into natural water bodies," said Johnson of CU-Boulder's ecology and evolutionary biology department.

The researchers wrote in the study that "reservoir construction and the conversion of free-flowing rivers to standing waters may ultimately facilitate the spread of invasive species across the landscape."

The team looked at data from 4,200 lakes and more than 1,000 impoundments across Wisconsin and the Upper Peninsula of Michigan.

The study showed non-indigenous species are up to 300 times more likely to occur in impoundments than in natural lakes, increasing the invasion risks for natural lakes.

"Collectively, these results suggest the benefits of building more reservoirs should be carefully balanced against the potential negative consequences, including increased biological invasions," Johnson said. (ANI)