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Getting elodea out of a lake is hard. Technicians have to treat the water with herbicide, and first they have to collect detailed data on the lake, including how fast its water flows, so the chemicals can be applied as safely as possible. Then equipment and people must be moved to remote places, and the site staffed continuously to watch the herbicide's effects. "It's a long and expensive process," said Anna O'Brien, the National Park Service's invasive plant management coordinator in Alaska. So the NPS looks for elodea before it can spread.
VIDEO: Student Conservation Association interns surveyed Wonder Lake in Denali National Park for invasive elodea. NPS.
Wonder Lake in Denali National Park. Credit: NPS/Emily Mesner.
The weed
Elodea is the first aquatic invasive plant documented in Alaska. It is hardy and spreads easily, most often as small fragments caught on boats or floatplanes. Once established, it can carpet a lake bottom, crowd out native plants and change fish habitat. A 2023 study found that juvenile coho salmon in a lake infested with elodea ate differently and grew less than their peers in lakes with only native plants. "It affects their life cycle," said Liam Irvin, one of the surveyors.
A dense mat of elodea under water. Credit: Nicole Swenson/USFWS.
A lake worth protecting
Wonder Lake shows what is at stake. Mount McKinley, the tallest mountain in North America, towers over the 2.6-mile-long lake. Fireweed, dwarf birch, blueberries and spruce line its banks; lake trout, Arctic grayling, beavers and trumpeter swans live there. On still, clear days the mountain is reflected in its dark water.
In the summer of 2024, Student Conservation Association interns Liam Irvin and Sam Schroeter and NPS crew lead Benjamin Wright — one of three invasive plant crews — surveyed it in the rain. They paddled to set points across the lake to scan the water below. Where they could not see the bottom, they threw out two metal rake heads welded back to back, let the tool sink, and dragged it in to check for long, viny strands of elodea.
"So far Denali is elodea free!" said Elysia Nitsch, an invasive plant management intern in Denali who helped with the survey.
Getting there
Crews go where park managers see the greatest need: lakes that get a lot of floatplane or boat traffic. That summer they surveyed high-risk lakes in Gates of the Arctic, Wrangell-St. Elias, Kenai Fjords, Lake Clark and Denali national parks. A lake takes a few days, and getting to it often means a flight in a small plane. "Many of these locations are not accessible by road, and floatplanes can spread elodea," O'Brien said. Even Wonder Lake, beside the Denali Park Road, can currently be reached only by plane, because of the Pretty Rocks landslide.
A floatplane in Lake Clark National Park. Credit: NPS.
More crews, more lakes
| Before | Now |
|---|---|
| surveys through an agreement with the University of Alaska Anchorage, led by Justin Fulkerson, which wrote the standardized elodea survey protocol | NPS crews carry out that same protocol |
| a handful of lakes a year | traveling crews, paid for by the Bipartisan Infrastructure Law |
"We're able to have traveling crews who can lay eyes on water bodies that we haven't been able to lay eyes on in more than a decade and some that we've never visited before," O'Brien said.
The crews have found no elodea in Alaska's national parks so far. But it has been detected elsewhere in the state, and since floatplanes carry it, it could reach any part of Alaska. Found early, it can be stopped.
While they are out, the crews also collect water samples for fish biologists, insects for the University of Alaska bee atlas, native seeds for future revegetation and dragonfly larvae for mercury analysis. They also record invasive plants on land, for a long-term inventory supported by the Inflation Reduction Act.
Interns Liam Irvin, Sam Schroeter, and Elysia Nitsch spent the summer outside, protecting Alaska national parks from invasive species. NPS Photo / Ron Bend.
"I can walk away from every single day knowing that I've helped and done something meaningful," Schroeter said.
Sources
Based on "Proactive, early detection could protect Alaska's lakes from invasive elodea" by Laura Vachula (October 2024), a writing partner with the National Park Service's Natural Resource Stewardship & Science Directorate; a work of the United States government in the public domain. Pictures an earlier version of this page left out were restored on 2026-09-26.
- The film and any audio are the National Park Service's own files, from the source page.
Dans ces publicationsDenali National Park & Preserve
Licence : CC0 1.0 (domaine public) · Adapté de www.nps.gov
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