Sep 22, 2016 02:54PM
Move a mussel: Mississippi River mussels relocated for I-74 bridge
By Anthony Watt
Sara Schmuecker, a U.S. Fish and Wildlife Service biologist, quickly recognized the species: pink heelsplitter, white heelsplitter, wabash pigtoe and pimpleback. They were as individual as their names. Some of their shells were rounded, smooth and long. Some were broad, humped and lumpy.
One little, warty, tan fellow — an inch-long, if that — caught Schmuecker's attention. She lifted it in her hand.
"It's a baby mapleleaf," she says. "It's tiny!"
The mapleleaf and its strange-looking neighbors were just a few dozen of the several hundred mussels that divers removed Aug. 2 from a stretch of the Mississippi River between Moline and Bettendorf. It was the second day of a massive relocation project expected to move about 450,000 mussels by the time it is finished this month.
The mussel bed is in the path of the new Interstate 74 bridge between Illinois and Iowa. Construction on the span is to begin next year. The joint effort of Illinois and Iowa has an overall cost estimated at $1.2 billion.
Some of the mussels in the project's path are specimens of federally or state endangered or threatened species. They must be moved to nearby places in the river that experts say are as mussel-friendly.
Three federally endangered mussels species — Higgins eye pearlymussel, sheepnose and spectaclecase — are in the bridge project area. Also present are butterfly mussels, which are listed as threatened in both states, and black sandshell mussels, which are listed as threatened in Illinois.
The removals are being done by hand. Because of the poor underwater visibility, divers from Ecological Specialists, a company specializing in the work, were bringing up all species, common and rare.
All of them will be moved to new locations, says Heidi Woeber, also a U.S. Fish and Wildlife Service biologist.
The work in August exemplified the routine. Divers brought bags of mussels, living and dead, to a barge where the live animals received an initial sort and cleaning. That included removing unwanted hitchhikers: invasive zebra mussels that compete for food and habitat. According to Fish and Wildlife, zebra mussels can cluster on a native mussel and prevent it from opening its shell to eat or breathe.
Once cleaned, the removed mussels were shipped to shore for identification and marking to help future observation, then they were separated into groups for relocation. During the process, the mussels were kept in aerated tanks to keep them alive.
About 1 million mussels are believed to live in the new bridge footprint and the region around it, Woeber says. The vast majority of them will be of the 20 or so common species, Woeber says. Only 5,000 to 7,000 endangered or threatened mussels are expected to be found in the area. Though fewer than their common cousins, they are are important overall to the survival of their declining species, she says.
As of early September, 75,000 mussels had been moved, Woeber says. Of those, 368 were Higgins eye, 30 were sheepnose, and there were 22 spectaclecase.
Another removal effort will occur before the old I-74 bridge is demolished in 2021, she says.
The mussels being moved are from areas deemed most at risk by the bridge project, according to Mary Kay Solberg, senior environmental specialist for the Iowa Department of Transportation. Those in less threatened portions of the construction zone will not be moved, but will be monitored.
Some fatalities are expected.
Mussels perform several functions in their ecosystems, including as a measure of the health of the rivers and streams.
"They become like the canary in the coal mine," Woeber says.
Anthony Watt is a writer on staff with The Dispatch and Rock Island Argus newspapers.
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