Invasive elodea species intrigues economist

Efforts to eradicate the invasive aquatic plant “Elodea” have had mixed results. Herbicides are being considered in Fairbanks, after mechanical means proved unsuccessful there, while on the Kenai Peninsula, the plant is all but gone. To date, the effects of the plant on Alaska’s environment have been measured in terms of its impact on fresh water resources, but now an economist at ISER [Institute of Social and Economic Research] is working to analyze the risk , and the economic implications, of the plant’s spread to salmon producing lakes.

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(Photo courtesy of Alaska Fish and Game)
(Photo courtesy of Alaska Fish and Game)

Someone, sometime in the past, dumped a goldfish tank into Chena Slough in Fairbanks.. and the results have been alarming. Elodea, a typical household aquarium plant, is commonly seen in goldfish bowls, but it has gone wild in Alaska.

“This plant is really adapting to Alaska conditions. And it has been found in many places to survive even in ice, and to be really vibrant even in the winter under two of more feet of ice with snow cover on top,” Tobias Schworer commented.

Schworer is neither a botanist nor a fisheries biologist. He works with data in a cramped ISER office in Anchorage, surrounded by computer monitors. Schworer is mapping elodea’s progress.. tracking its spread from one Alaska lake to another as part of a research project. Why? Because of the state’s salmon industry.

Elodea grows so fast in Alaska that it has been blamed for destroying fish habitat in some places.. like Chena Slough, where grayling habitat has diminished because the heavy, matted masses of elodea absorb the nutrients fish thrive on. That’s chilling news to an industry that depends on fresh water lakes and streams to replenish it’s salmon supply.

According to the Sea Grant Newsletter, elodea grows along lakeshores, in sandy habitats where salmon like to spawn. Spawning can be impaired as the density of elodea increases and crowds out fish habitats.

But, Schworer, ever the scientist, says there are many unknowns. He says there could be another scenario:

“On the other side, it has positive effects in terms of it increases productivity, there could be more prey for certain salmon species,” Schworer said. “There’s anecdotal evidence that it enhances this little water snail that cohos and whitefish like to eat.”

On one hand, elodea can serve as a nursery for juvenile salmon, which may benefit salmon populations, he says.  But the plant can dangerously affect the oxygen levels critical for fish survival.

Elodea first showed up in Eyak Lake in Cordova in 1982. It probably hitched a ride out on the floats of an air taxi… later appearing in Sand Lake and Lake Hood in Anchorage. Schworer’s elodea pathway map will help floatplane pilots as well, because they don’t want to land on lakes choked with the stuff,  and that has an economic impact on where the air taxis can travel.

Three lakes on the Kenai were infested with the plant, but have been rated cleared as of this summer, according to Heather Stewart, the state’s invasive plant coordinator.
Efforts to get rid of it mechanically in Chena Slough were not as successful, she said, and an herbicide assault will be next.

“Right now, we are hashing out the environmental assessment for the work, to propose to use fluridone in Chena Lake, Chena Slough and Tokchakat Sough in Fairbanks,” Stewart said.

Schworer hopes his ISER research will help state Department of Natural Resources managers stop the spread of the plant. He says there is an interesting slant to the elodea story, in that Alaska’s elodea may become a separate variety.

“Researchers have tried to grow elodea from the Kenai lakes in the lab, and used their methods to grow the elodea at much higher temperatures than found in Alaska, and the elodea from the lakes on the Kenai did not grow as the researchers expected, and it turned out that once they dropped the temperatures in the tanks, the elodea suddenly took off,” Schworer said.

Meanwhile, elodea has rooted in remote Alexander Lake in the the Matanuska Susitna area. Stewart says eradication efforts could begin this summer, when federal agents approve an herbicide plan.  Alexander Lake also hosts invasive Northern Pike, a fish which seems to like elodea, Schworer said, giving Mat-Su a one – two invasive punch.

“Humans are the main drivers and distributors of this,”  he said, referring to the spread of the invasive plant.

The spread of the plant is blamed on floatplanes, or  boats, as they travel from one lake to another, Schworer said.

He said the cost of invasive species eradication in the lower 48 is in the billions of dollars every year, and conversely, the invasive problem is just getting started in Alaska and that could bring opportunities for a new industry based on prevention and response to invasives. Schworer’s research data could be useful in that respect as well, he said. The ISER elodea data is expected to be published sometime next year.