Zebra mussels found in Lake Hiawatha

‘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.