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Just a year and a half after quagga mussels first were discovered to
have colonized the West -- home to some of the most extensive water
delivery infrastructure in the country -- the dime-sized mollusks have
spread to new water bodies, and water managers are experimenting with
new ways to keep the invasion in check.
Quagga mussels, which are closely related to zebra mussels, have
colonized several reservoirs in the Lower Colorado River Basin and a
few other areas in the West, but water managers are hoping they can
contain the problem through inspections and an aggressive public
education campaign.
Quagga mussels arrived in Lake Mead in
2006, most likely on a boat that had plied infested waters in the Great
Lakes, where both quagga and zebra mussels have wreaked havoc for
years. The mollusk's arrival in Lake Mead, part of Glen Canyon National
Recreation Area, marked the first time invasive mussels established a
population west of the continental divide. In the ensuing 20 months,
they have expanded down the Colorado River, through two other
reservoirs -- Lakes Mohave and Havasu. The mollusks have also colonized
Pueblo Lake in Colorado, and reservoirs in the San Diego area.
The
spread of quagga mussels has state and federal water managers concerned
that water infrastructure and aquatic ecosystems will be taken over by
the mussels, which have already caused billions of dollars of damage in
the Great Lakes area.
"They have the potential to really
increase operation and maintenance costs," said Peter Soeth of
Reclamation's commissioner's office in Denver, Colo. "They will tend to
close off pipes and clog gates."
Jeff Lane of the Salt River
Project, which provides water and hydroelectricity to the Phoenix
metropolitan area, said that if quagga mussels invade its delivery
pipes, they could disrupt water deliveries.
"We're trying to be proactive so we can hopefully head them off at the pass, so to speak," Lane said.
Infrastructure, ecosystem concerns
Dave Britton,
assistant aquatic invasive species coordinator for the U.S. Fish and
Wildlife Service's Southwest region, said it is "very probable" that
water delivery infrastructure at Lake Mead and the Lower Colorado River
will become clogged with quagga mussels, slowing or stopping water flow.
Britton is worried about the harm to ecosystems as well: Quagga
mussels are filter feeders, meaning they scoop up phytoplankton,
depleting water bodies of nutrients and out-competing native mussels.
And since they attach to any hard surface, they glom on to turtles and
crustaceans as well as pipes and waterworks.
Mark Olson,
project leader at the Willow Beach National Fish Hatchery, just south
of Lake Mead, said the hatchery had to stop raising razorback suckers
for use in reintroduction and recovery efforts for the endangered fish
after quagga mussels begun clogging screens and other equipment.
"We
used to take the larvae directly from the river, raise them a few weeks
and then ship them to a facility out of state," Olson said. "We can't
do that anymore because of the infestation." Another, captive stock of
suckers from a different hatchery where quaggas have not been detected
is now used for the project, he added.
Quagga and zebra
mussels, which belong to the same genus, both display black and white
"stripes" and attach to hard surfaces -- common for marine bivalves but
not for native freshwater mollusks. They are native to Eurasia, and
most likely hitched a ride in the ballast water of ships. Quagga
mussels arrived later than zebra mussels but have now spread farther
west than their slightly more diminutive cousins.
While it is
virtually impossible to eradicate quagga mussels from large reservoirs,
water managers and biologists are hoping to keep the tiny bivalves from
spreading. While little is known about how the mussels are adapting to
the Southwest, biologists suspect they may thrive in warmer water.
"It
hasn't affected operations yet, but we're doing research on protective
measures we can take to reduce their impacts on our facilities," Soeth
said. Researchers are trying various coatings that prevent mussels from
attaching to structures, and are experimenting with ways to control the
bivalves. This fall, Reclamation plans to conduct an experiment that
would use a certain type of bacteria to kill quagga mussels without
harming other organisms. The bacteria, which has been effective in
killing zebra mussels, will be unleashed on quagga mussels in Davis
Lake, Soeth said.
"What we're seeing here in the western
United States is one size does not fit all," Soeth said. "We're seeing
different things on growth rates, how big they're getting, how fast
they're getting. And we're trying to understand why that is."
Federal
water managers also have launched an educational campaign warning
boaters to drain water from their crafts and clean the hull to avoid
carrying mussels to new water bodies. A similar campaign in Minnesota
has kept zebra mussels, which invaded the state's eastern border two
decades ago, from spreading inland.
Quagga mussels carried on a single boat can infest an entire lake.
The
Metropolitan Water District of California, which takes water from Lake
Havasu in Arizona, has used chlorination to kill quagga mussels, but
Reclamation cannot use that method at its dams because it would also
harm plant life and aquatic life downstream, Walsh said.
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