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Every year, the Great Lakes region spends up to half a billion dollars fighting invasive aquatic mollusks. The tiny mussels clog up pipes for drinking water and power plants, and they're a threat to fish like salmon. They've also been migrating across the country. Last year, they reached the Columbia River Basin in the Northwest, the only major river system in the U.S. without an established population of mussels. Boise State Public Radio's Rachel Cohen reports on efforts to eradicate them.
RACHEL COHEN, BYLINE: Michael Stephenson has spent years worrying about a tiny invasive creature smaller than a fingernail. Then last fall, they arrived. The larval form of quagga mussels and one adult were found in the Snake River, which feeds the Columbia.
MICHAEL STEPHENSON: I'm feeling very anxious about it.
COHEN: Stephenson works for Idaho Power, the state's largest utility, serving 1 1/2 million people. It operates 15 hydropower plants downstream of where the mussels were detected. He says the small bivalves are a big problem. They spread rapidly and attach to pretty much any surface in the water. One estimate says they'll cost the Northwest $500 million a year to deal with. Atop one of the Idaho Power dams, Stephenson points to a metal filter between the reservoir and the powerhouse.
STEPHENSON: Probably 2-inch round steel bars. As the quagga mussels grow on them, those gaps between the bars will close down, which will reduce the water that's going into the dam.
COHEN: The company currently uses a mechanical rake to remove sticks and vegetation, but prying quagga mussels off could require scuba divers. It's also considering buying special ultraviolet lights to kill baby mussels floating through its facilities.
STEPHENSON: If we get an infestation in the Snake River, it may be the biggest problem we've dealt with yet as far as infrastructural issues.
COHEN: Last fall, Idaho poured a copper-based chemical into the river to try to eradicate the mussels. Similar toxins have been proven to kill mussels elsewhere, but this treatment in a major river was unprecedented.
NIC ZURFLUH: And that's been weighing quite a bit on my mind, just gauging how effective the treatment was last fall.
COHEN: Nic Zurfluh, the invasive species lead at the Idaho Department of Agriculture, says it's been a long winter of waiting to see if the chemical worked.
ZURFLUH: Not having detections, I would take that as really great news, but just knowing - you know, that's not going to tell the full picture until we go by a little while with non-detects.
COHEN: The tiny mussels are hard to find. It might take a few months, even a few years, to get an all-clear. If the mussels are still in the Snake River and make it down into the Columbia, it would increase risk to fish that migrate from inland spawning grounds to the ocean and bring vital nutrients back, nutrients the quagga mussels absorb. Anthony Capetillo is an invasive species biologist with the Nez Perce Tribe and a tribal member.
ANTHONY CAPETILLO: If the quagga mussels are sucking all the oxygen and all the nutrients out of the water, then that takes away from the fish, so they're not able to grow as they usually would.
COHEN: Salmon, in particular, he says, are already suffering because of dams and climate change.
CAPETILLO: All the money that we've been putting into all these projects to get these salmon and steelhead and lamprey back into these waters, all of that could potentially be for nothing if we allow these invasives to come and take hold.
COHEN: Idaho officials hope their efforts have prevented that scenario. At this waterfront near Twin Falls, they're requiring all boats entering and exiting the river to be washed down because it would just take a mussel from out of state hitching a ride on a boat or kayak for a new introduction tomorrow.
For NPR News, I'm Rachel Cohen.
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