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Lake-choking invasive weed makes it to Mat-Su

  • Author: Zaz Hollander
  • Updated: September 28, 2016
  • Published October 16, 2014

WASILLA -- Scientists last month discovered an invasive and potentially fish-threatening plant called elodea for the first time in the Matanuska-Susitna Borough.

The alien invader turned up in shallow Alexander Lake, a remote and once-legendary salmon stronghold in the Susitna River system more recently beset by northern pike. The voracious non-native fish is decimating salmon stocks in parts of the state including the Mat-Su -- and pike like the shelter of plants like elodea.

Officials say it's not absolutely clear how the weed came to Alexander Lake, which is accessible only by boat or floatplane, but there is a possible link to an established infestation in Anchorage's Sand Lake.

The area where elodea showed up is near a cabin owned by a floatplane pilot who lives on Sand Lake, state and federal officials say.

"We can't really point the finger," said Cecil Rich, fisheries and aquatic invasive species coordinator with the U.S. Fish and Wildlife Service in Anchorage. "He's aware of it. Pretty much all the floatplane pilots on Sand Lake are aware of it. It's just very difficult to be certain you don't have any on your floatplane when you take off."

The discovery in Alexander Lake brings the total of slow-moving rivers and lakes infested with elodea in Alaska to 18.

Elodea, also known as waterweed, is a leafy green plant often seen undulating inside aquarium tanks.

But in lakes and slow-moving streams, elodea spreads easily and grows into dense, tangled mats of vegetation.

The mats foul floatplane rudders, complicate boat travel and choke out native plants, sometimes getting so thick that nearby property values take a hit. They also squeeze out salmon and other aquatic life, use up oxygen that fish need to survive -- and shelter predators like pike.

Elodea can be spread by boats, trailers, floatplanes, aquarium lovers and even school classes that use the plant for lessons, officials say. All it takes is a fragment to start a new bloom.

Officials say the spread of elodea emphasizes the need to squelch it in busy Anchorage lakes before it really gets going.

"We want to basically prevent anything like this, Alexander Lake, from happening again by managing the Anchorage lakes," said Heather Stewart, the Alaska Division of Agriculture's invasive weeds program manager.

Elodea was first spotted in Alaska in the early 1980s in Eyak Lake near Cordova but then dropped off the radar until dense mats showed up in Chena Slough near Fairbanks in 2010.

That put managers on alert, and they found more elodea in three Anchorage lakes -- Sand Lake, along with Little Campbell and DeLong lakes -- and three on the Kenai Peninsula.

The state this year banned the import, sale, purchase and release into Alaska waters of two elodea species.

The state also publishes an identification guide and separate instructions to help boaters and pilots guard against spreading elodea.

Tips include trying not to motor or taxi through thick aquatic vegetation, raising and lowering plane rudders after takeoff from a water body to dislodge any fragments, and checking trailers or rudders for plant fragments, according to an alert sent last month to Valley lake-monitoring volunteers by Mat-Su Borough watershed coordinator Melanie Trost.

The elodea fight is underway in some places and still in the planning stages in others.

But the war on elodea is short on cash.

The Legislature during the last session didn't approve a state request for elodea funding, Stewart said.

The capital budget did, however, give $400,000 to the Kenai Peninsula Borough for elodea eradication. The effort was also funded by some smaller grants and other funding sources.

Kenai officials this year applied the herbicides fluridone and diquat to Stormy, Daniels and Beck lakes.

It's working.

Elizabeth Bella, a Kenai National Wildlife Refuge ecologist who's involved with elodea eradication, reported "complete destruction" in Beck Lake and just a few brittle, browning traces of the weed in Daniels Lake. Stormy Lake, which had the highest concentration of elodea, still has some live plants but a last dose of herbicide just went in and Bella said she expects it to keep working under the ice all winter to knock back the survivors.

The multi-agency Kenai elodea eradicators worked closely with the herbicide manufacturer to calculate the most conservative application they could use, she said. They invited a California aquatics expert up.

"The other pivotal piece was getting ... the public involved right away, like from day one, basically," Bella said.

Stewart says she hopes to use a similar herbicide tactic next spring on Alexander Lake but needs to get funding first. She's working with the Mat-Su Fish Habitat Partnership to raise about $50,000.

Multiple agencies in Fairbanks are exploring the feasibility of mechanical control in the Chena Slough, while other groups in Anchorage, Mat-Su and Cordova are mapping out comprehensive management plans and surveying high-risk waterways, according to the Alaska Division of Agriculture.

Rich said he worked with the Alaska Department of Fish and Game and Department of Natural Resources to do a plant survey on Sand Lake. Agencies have held a few public meetings on elodea. The state is pulling together a technical work group on the problem, he said.

Stewart said she and Alaska Plant Materials Center manager Brianne Blackburn are creating a plan to evaluate all options, including budget, to get more information to the public and agencies. There's not a lot of funding for elodea eradication in lakes, she said.

For now, the elodea in isolated Alexander Lake is fairly sparse and mixed with plenty of native vegetation, Stewart said.

"Which is great," she said. "That's why we're trying to jump on this so quickly. It hasn't basically gotten to the point of no return."

The state hopes the public will answer a brief survey on elodea.