Article

Proactive, early detection could protect Alaska’s lakes from invasive elodea

Denali National Park & Preserve

By Laura Vachula, October 2024
A large, calm lake reflecting glaciated mountains of the Alaska range in its water.
Wonder Lake in Denali National Park.

NPS Photo / Emily Mesner

Mount McKinley, the tallest mountain in North America, towers over Wonder Lake. Pink fireweed flowers, shrubby dwarf birch, blueberries, and spruce trees line the banks of the 2.6-mile-long lake where lake trout, Arctic grayling, beavers, and trumpeter swans make their home in Denali National Park. On still, blue-sky days, the mountain reflects in the clear, dark water for an iconic view.

But elodea, a water weed, could change things. It’s the first aquatic invasive plant in Alaska, and scientists have observed its detrimental effects on underwater habitats and fish populations, including salmon. Proactively preventing elodea from spreading through Alaska’s lakes is critical to protect healthy ecosystems from demise.

For Student Conservation Association interns Liam Irvin and Sam Schroeter, this means a summer spent waking up in tents and paddling through remote lakes in Alaska national parks. Their mission: Find elodea before it proliferates.

Is there elodea in Wonder Lake?

Dense mat of invasive elodea growing underwater.
Elodea is the first aquatic invasive plant that has been documented in Alaska.

Nicole Swenson / USFWS

Elodea is hardy and can spread easily, most commonly by small fragments that attach to boats or floatplanes. Once it takes hold in a new environment, it can cover the lake bottom, outcompete native plants, and alter fish habitat. A 2023 study found that juvenile coho salmon living in an elodea infested lake experienced changes in their diets and reduced growth compared to their peers in lakes with only native plants.

“It affects their life cycle,” Irvin said.

Irvin and Schroeter, along with National Park Service (NPS) crew lead Benjamin Wright, made up one of three invasive plant crews traveling to lakes throughout Alaska this summer.

“We’re surveying where the park managers tell us they have the greatest need—places that receive a lot of floatplane or boat action,” said Anna O’Brien, NPS invasive plant management coordinator in Alaska.

This year the crews have been to high-risk lakes in Gates of the Arctic National Park, Wrangell-St. Elias National Park, Kenai Fjords National Park, Lake Clark National Park, and Denali National Park.

As rain drizzled on the crew at Wonder Lake, they paddled to predetermined points throughout the water to scan the ecosystem below. In areas where they couldn’t see to the very bottom, they tossed out a tool consisting of two metal rake heads welded back-to-back. After letting it sink, they dragged it in to see if they captured any long, viny elodea.

“So far Denali is elodea free!” said Elysia Nitsch, invasive plant management intern in Denali, who also helped with the survey at Wonder Lake.
Proactive, Early Detection Could Protect Alaska’s Lakes from Invasive Elodea
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      VIDEO: Student Conservation Association interns surveyed Wonder Lake in Denali National Park for invasive elodea.

      Bipartisan Infrastructure Law increases capacity

      It typically takes a few days to survey a lake, and the travel to and from often requires flying on small planes.

      "Many of these locations are not accessible by road, and floatplanes can spread elodea,” O’Brien said.

      Floatplanes are popular in Alaska, where pilots can explore remote parts of the wilderness by landing on water, unrestricted by man-made airstrips. This means that the elodea crews need to venture to these locations as well. Even Wonder Lake, which is adjacent to the Denali Park Road, is currently only accessible by plane due to the Pretty Rocks landslide.
      Plane floating on a clear body of water between mountains concealed by fog.
      Float plane in Lake Clark National Park.

      NPS Photo

      Between the staff time, travel costs, and logistics, each elodea survey is a considerable effort.

      “These crews wouldn’t have been possible without funding from the Bipartisan Infrastructure Law,” O’Brien said.

      Prior elodea efforts in Alaska national parks had been completed through an agreement with the University of Alaska Anchorage. Led by Justin Fulkerson, the university developed a standardized elodea survey protocol, which O’Brien’s crews now execute. As part of the partnership, the university performed some elodea surveys, but only had the capacity to visit a handful of lakes each year.

      With dedicated funding through the Bipartisan Infrastructure Law, the National Park Service can now widen the reach and increase chances of detecting elodea early.

      “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.

      Time well spent

      Fortunately, the crews haven’t discovered any elodea in Alaska national parks, but it’s important to remain vigilant. Scientists have detected elodea in other bodies of water in the state, and since it can be spread by floatplanes, the plant could literally fly through the air to any part of Alaska. If they can find elodea early, they have a better chance of stopping it in its tracks and preventing further spreading.

      Eliminating elodea requires technicians to treat the body of water with herbicide, but they first need to collect extensive data on the lake environment, including water flow rates, so that the chemicals can be administered as safely as possible. The approach also requires moving large equipment and people to remote locations, as well as continuously staffing the area to monitor the impacts of the herbicide.

      “It’s a long and expensive process,” O’Brien said. The efforts required to eradicate the plant highlights the need for her crews to proactively monitor for it. And while they’re out at these remote locations, the crews have the capacity to support other projects, collecting water samples for fish biologists, insects for the University of Alaska bee atlas, native seeds for future revegetation projects, and dragonfly larvae for mercury analysis. They also look for invasive plants growing on land as part of a long-term effort to inventory and manage terrestrial infestations in national parks—a program currently bolstered by the Inflation Reduction Act.
      Young adults wearing waders face a mountain range.
      Interns Liam Irvin, Sam Schroeter, and Elysia Nitsch spent the summer outside, protecting Alaska national parks from invasive species.

      NPS Photo / Ron Bend

      For Irvin and Schroeter, it’s the experience of a lifetime. They’ve had the opportunity to travel throughout the state, build professional relationships, and learn new skills—invaluable for the college students. And the cherry on top: The work they're doing is making a difference.

      “I can walk away from every single day knowing that I’ve helped and done something meaningful,” Schroeter said.
      Female hiker with hiking poles smiling at the camera
      Laura Vachula
      Laura Vachula is a writing partner with the National Park Service’s Natural Resource Stewardship & Science Directorate.

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      Last updated: February 1, 2025