‘It was inevitable’
that the invasive species make its way to Minneapolis, according to MPRB
by Tesha M. Christensen
Zebra mussels have officially infested Minneapolis waters.
They have been found in Lake Hiawatha.
Minneapolis Park and Recreation Board (MPRB) water quality
workers found several of the small, invasive mollusks Aug. 28 on a plate
submerged in the lake as a detection device. Following that discovery, MPRB
staff throughly searched both upstream and downstream to see if there were more
in the city.
“Mussels were found on the underside of the Lake Hiawatha
fishing dock where the sampler is located, on beach buoys, and on large rocks
at a few locations just downstream of the lake – but none were found upstream
to Xerxes Avenue,”observed Debra Lynn Pilger of the Minneapolis Parks and
Recreation Board.
“Some might suspect that because Lake Hiawatha sees very
little boat traffic, and has no boat launch, it would be immune from this type
of infestation,” observed Standish-Ericsson Neighborhood Association
Neighborhood Coordinator Bob Kambeitz.
“But since the Minnehaha Creek flows into and out of Lake
Hiawatha, it’s not surprising that zebra mussels would work their way into the
lake from upstream at Lake Minnetonka.”
The Minneapolis Parks and Recreation Board has been expecting
to find zebra mussels since 2010 when they were discovered in Lake Minnetonka
and the entire watershed was declared infested. Minnehaha Creek flows from Lake
Minnetonka through Lake Hiawatha to the Mississippi River, which has been
designated as a zebra mussel infested water body by the Minnesota Department of
Natural Resources (MNDNR).
At the end of the 2012 sampling season, zebra mussels had
made their way to Brownsdale Dam, about a mile upstream from the Minneapolis
city limits.
“It was inevitable,”said Pilger. “It was just a matter of
time until they got here.”
NO
TREATMENT
There is no treatment for zebra mussels, according to Pilger.
“We will be focusing our efforts on keeping them out of other lakes,” she said.
While the creek flows through Lake Hiawathaa, at Lake Nokomis
water only flows out. According to Doug Walter of the Nokomis East Neighborhood
Association, “The lake’s level is kept higher than that of the creek and excess
water flows over a dam to prevent the possibility of invasive species entering
Lake Nokomis.
“Up until a year or so ago, there was an inflatable bladder
that automatically raised a pivoted weir (or gate, if you will) to keep the
lake’s discharge above the creek.
It used a complicated system of electronic water level sensors and an
air compressor with the requisite to adjust the height. However, the equipment
proved trouble-prone and expensive to maintain (let alone not working during
heavy storms where power was knocked out). That was replaced with a fixed dam.”
PLAN
FOR PREVENTION
Zebra mussels cause problems for both swimmers, who are cut
by the sharp shells, and anglers, who lose tackle.Groups of mussels can damage buoys, dock supports,
boat parts and other underwater structures. A native to Russia, they spread
easily and have few predators.
In 2012, the MPRB Board of Commission began inspecting boats
at public launches at Lake
Harriet, Lake Calhoun and Lake Nokomis, and placed bait disposal receptacles at
many of the city’s most popular fishing spots in an attempt to block the spread
of zebra mussels.
The discovery of zebra mussels in Lake Hiawatha underscores
the need for continued diligence in complying with the state’s laws to prevent
and curb the spread of invasive species, according to the Parks and Recreation
Department.
Anglers, boaters and other recreationists must remove all
aquatic plants, zebra mussels, and other prohibited invasive species, drain
water from all water equipment including portable bait containers, and drain
bilges and livewells by removing the drain plug before leaving the boat
landing.
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SIDEBAR/WEB SITE INFORMATION
ABOUT ZEBRA MUSSELS
Zebra mussels are native to
freshwater lakes and rivers of southeastern Russia and traveled to the United
States via ballast water in freighter ships. They spread easily and have few predators.
Zebra mussels can easily
outcompete our native mussels because they not need a larval host, and they
have a much more rapid growth rate in addition to a shorter time to
maturity. In their larval stage
they are able to spread by floating through the water, eventually settling on
hard surfaces and reproducing after just short of a year.
Zebra mussels can have many
impacts on water bodies.
Initially, the mussels can increase the water clarity by filtering out
large amounts of some types of algae.
Negative impacts can range from sharp shells collecting on beaches,
growth on structures that may require cleaning, waterfowl die offs, increased
blue-green algae blooms (which zebra mussels do not prefer to eat), changes in
the fish community structure, and increased aquatic plant growth.
STOP THE SPREAD
To help prevent the spread of
zebra mussels and other aquatic invasive species:
• Always
remember to Clean, Drain, and completely Dry any equipment moving between water
bodies.
• Do
not move equipment from Lakes Nokomis and Hiawatha to other water bodies –
always move from non-infested to infested waters.
• Be
especially conscientious about the potential of transferring AIS from the creek
or Hiawatha to Lake Nokomis.
• As
buoys and structures are removed from lakes this fall, please inspect them
carefully for anything that could be zebra mussels and report any findings to
Environmental Operations.
