Zebra mussels talk draws full house

By Casey Merkwan

Concerned community members and experts packed a room at the Chanhassen Community Center last week to learn more about the dreaded zebra mussels.

More than 50 people attended a forum that featured speakers Steve McComas, an aquatic biologist and ecologist, Luke Skinner from the Minnesota Department of Natural Resources and Eric Evenson, district administrator of the Minnehaha Creek Watershed District to talk about the problem of zebra mussels and what’s next for Minnesota lakes.

Skinner said there is no safe way to eradicate zebra mussels, so the focus is on preventing any further spreading.

“There’s a lot of concern about a lot of invasive species but right now the zebra mussel is the poster child for spreading in the state,” Skinner said.

Skinner said it is possible to kill off zebra mussels but there’s risk of killing other species. He also said the larger the lake the harder they are to control.

“In a lake like this [Minnetonka] with this many bays and islands and stuff, the reality of trying to manage it here is it’s not going to happen,” he said.

Since the discovery of zebra mussels in July of last year, experts say the key is to prevent them from spreading.

It’s possible the non-native invasive species have been in Lake Minnetonka for more than two years.

“They were also found on the other side of the dam of Lake Minnetonka so theoretically Minnehaha Creek is considered to be infested as well,” McComas said.

Zebra mussels originated from the Black and Caspian seas in Europe. It is suspected that the species traveled to the United States via cargo ships in the late 1980s.

After the discovery of the zebra mussels in July, agencies performed an enhanced assessment to determine the distribution of the infestation and to find adult zebra mussels to lead them to a breeding point.

“They were fairly hard to find,” McComas said. “In a big lake it really is looking for a needle in a haystack trying to find a breeding population.”

Divers didn’t find a breeding spot. McComas said there was 100 hours of dive time, 30-40 volunteers and 20-30 spots where zebra mussels were found in Lake Minnetonka, mostly on the east side of the lake.

Lake Minnetonka and neighboring lakes were also assessed for how hospitable the lakes were for zebra mussel population growth.

McComas said the calcium levels in all 26 bays of Lake Minnetonka were high enough that they could support optimal growth of zebra mussels.

Other factors that are optimal for zebra mussel growth are PH levels, the right concentration of chlorophyll and bottom conditions.

Zebra mussels attach easily to hard surfaces with substrate, for example rocks. If the bottom of the lake is sand and silt, the mussels can attach to each other as well.

Lake Minnetonka has the conditions that would support moderate growth of zebra mussels and 43 percent of lake bottom could be colonized, McComas said.

Christmas Lake has the potential to have 60 percent of the lake bottom colonized, according to McComas.

Zebra mussels kill native mussels and also compete with young fish for food. They can also block underwater pipes.

McComas said zebra mussels start spawning when the water temperature reaches 54 degrees.

Currently, water temperatures are in the high 30s. By late May the water temperatures will raise to optimal spawning time.

“This isn’t something that the state can do on their own, this isn’t something the watershed district can do on their own, this isn’t something that counties can do on their own. This is going to have a coordinated effort, a cooperative effort to really get anything to happen here and it is going to involve all the agencies, it’s also going to have to involve lake associations and individuals out there,” Evenson said.

As a result Evenson, Skinner and McComas emphasized the need to prevent further infestation of the zebra mussels.

Evenson suggested implementing a red lake, blue lake program to help stop spreading.

The program would use a red sticker to identify when a boat has been in waters infested with zebra mussels. A boat could not enter a lake without zebra mussels until inspected.

The legislature has also gotten involved: a new drain plug law took effect on July 1, 2010. The law states that a person leaving waters of the state must drain boat equipment by removing the drain plugs, bailers, valves or other devices that hold water.

On March 16, Gov. Mark Dayton announced his support for legislation that hopes to minimize the spread of aquatic invasive species.

The bill would require more thorough inspections, double penalties for violations, allow local law enforcement to retain civil penalty amounts for citations issued by their agency, require training for lake providers and require watercraft and operators to have a decal that lists invasive species rules, like a sticker.

The experts encouraged community members to vocalize their concerns with their elected representatives and to also educate their neighbors to slow the infestation of zebra mussels.

Zebra mussels in Lake Minnetonka

TOM MEERSMAN, Star Tribune

Zebra mussels have invaded Lake Minnetonka, a breach of the state’s defenses against invasive species that threatens to dramatically change the character of Minnesota’s 10th-largest lake within just a few years.

Department of Natural Resources biologists confirmed Wednesday that a small number of mussels are attached to rocks along the shore, and their size suggests that a reproducing population has been in the lake for at least a year.

In places where they’ve become established, the fingernail-sized mussels proliferate by the millions, consume food needed by fish, clog water intake pipes, ruin fish spawning beds and litter beaches and shallow areas with razor-sharp shells.

The mussels were found on the east side of Wayzata Bay near Hwy. 101. That’s not far from the lake’s outlet to Minnehaha Creek, raising fears that the mussels may spread into that waterway, or may have done so already. Minnehaha Creek is connected to lakes Nokomis and Hiawatha in Minneapolis.

For years DNR officials have worked with the Lake Minnetonka Conservation District and others to educate boaters and anglers to prevent the spread of zebra mussels. They also inspected boats and trailers and directed owners to remove plants, mussels and water from bait buckets and vessels that traveled in infested lakes and rivers. The efforts may have bought some time, but they didn’t stop the mussels’ entry into Minnetonka.

“Unfortunately, zebra mussels still found their way to the lake,” said Luke Skinner, supervisor of DNR’s invasive species program.

The discovery was dreaded news for Dick Osgood, president of the Lake Minnetonka Association, which represents about 600 lakeshore owners and businesses.

“This has been our fear all along, and keeping them out has been our top priority for the last ten years,” said Osgood.
Lake Minnetonka is the most heavily used lake in the state, he said, with an estimated 200,000 boats plying its channels, bays and open water annually.

With that amount of exposure, the discovery of mussels was not unexpected, said Osgood, but it was still a major disappointment.

“Bottom line is, I think they’re here to stay,” he said. “Not that we won’t do everything possible in rapid response, but I think it’ll change the lake forever.”

Osgood and representatives of the Minnehaha Creek Watershed District plan to do a quick assessment of the lake to see if they can find mussels in other places. There’s a chance, he said, that if they are only in one area, the mussels could be removed or killed before they spread further.

DNR officials said that the number of zebra mussels found was very low and that they would investigate the situation this week and beyond, including an extensive survey of the lake later this summer.

Osgood advocates limiting boat traffic in the infested waters, at least until the extent of the invasion is better understood.
In other places, he said, the discovery of zebra mussels is usually followed by 1 to 3 years of “lag time” in which a few more infested areas are found. At some point, usually about five years after the initial discovery, he said, the populations explode and the lakes start to change, sometimes unpredictably.

In some areas the numbers of different fish species increase or decrease, seeking a new balance as habitat and food sources change. Native mussels usually die out. And because zebra mussels constantly filter sediment and nutrients, water often becomes noticeably clearer.

That may please some, said Osgood, but it also means that light will penetrate deeper, boosting the growth of plants such as Eurasian water milfoil, an invasive that’s already a major nuisance and expense to control in Lake Minnetonka.

Resident spotted mussels

A local resident found the mussels in the lake early this week and reported them to the DNR. Skinner said that anyone else who finds mussels should contact the agency.

Zebra mussels are native to Eastern Europe and western Russia, and likely came to the Great Lakes in ballast water of ocean-going ships that traveled up the St. Lawrence Seaway. They were discovered near Detroit in 1988. Their first appearance in Minnesota was in 1989 in Duluth harbor, and they subsequently spread to 17 inland lakes, including Mille Lacs, Prior, and Le Homme Dieu and to portions of the Mississippi, St. Croix and Zumbro rivers.

Udai Singh, senior hydrologist and water quality specialist for the Minnehaha Creek Watershed District, said plans for what to do next are still very preliminary. If the mussels are firmly in the lake, he said, the district may install equipment at various locations downstream in Minnehaha Creek to check for them. The discovery in Minnetonka is “really unfortunate,” Singh said, and has already jump-started a new array of activities.

“Now since prevention is out the window, we will be more working in terms of control and management of them,” he said.
Tom Meersman •StarTribune