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Reducing the Threat of Elodea
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SourDough News | June 17, 2015
A rake head is used to sample Elodea and other aquatic vegetation. Photo by Kate Mohatt, Ecologist, USFS
A dense bed of Elodea growing in a pond off Eyak River. Photo by Kate Mohatt, Ecologist, USFS
A dense bed of Elodea growing in Martin Lake. Photo by Kate Mohatt, Ecologist, USFS.
The genus Elodea includes five species of submerged aquatic plants found in freshwater lakes and slow moving water. Two of these species, Canadian (E. canadensis) and western waterweed (E. nuttallii) are native to North America and their northern ranges extend to southern British Columbia. Hybridized versions of these species are often used in aquariums and for educational purposes. Based on the best available information, all species of Elodea (hereinafter referred to with the common name “elodea”) are considered not native to the state of Alaska.
Elodea is the first known aquatic invasive plant in the state. Outside its native range it has often compromised water quality, grown so abundantly that boat traffic is hindered, reduced dissolved oxygen, and severely impacted native fisheries. Further, only a plant fragment is needed to infest a water body because it reproduces vegetatively. Recognizing the threat, the Alaska Department of Natural Resources issued a statewide quarantine for both E. canadensis and E. nuttallii in March 2014.
The first record of elodea was from Eyak Lake in 1982. Vegetation sampling was conducted throughout the entire lake, however, the plant was only found in one location off Mavis Island. In 2011 and 2012, the U.S. Forest Service surveyed several locations throughout the lake, and found elodea to be present in nearly all areas surveyed. It is believed that it was originally introduced into the lake from an aquarium dump. In 2012, the Forest Service continued surveys for elodea beyond Eyak Lake and found it in McKinley Lake, Wooded Pond, Wrong Way Pond, Alaganik Slough, and Martin Lake. These surveys continued through summer 2014, where additional infestations were found in Bering Lake and several small ponds and sloughs off Eyak River and Alaganik Slough. The plant was not found in surveys of Little Martin, Tokun, Kushtaka, Pothole, or Elsner lakes. Surveys conducted across Prince William Sound in and the eastern half of the Kenai Peninsula also turned up no additional infestations.
Elodea is found in five areas across the state including Fairbanks, Anchorage, Kenai, and the Mat-Su Bourough in addition to the Copper River Delta. The Cordova infestations are currently known to be the oldest and most widespread in the state. The State of Alaska is in the process of developing a statewide strategic plan with the goal to eradicate these species from the Alaska. Herbicides are currently the only known effective treatment for this species.
This summer on the Chugach National Forest, we plan to continue with surveys across the Copper River Delta to determine the full extent of this infestation and continue to survey lakes across the forest. We will also be measuring infestation abundance in infested lakes and ponds throughout the growing season and looking at uninfested ponds and historic data to determine which native aquatic plant species are being displaced by this introduction. Additionally, the fisheries crew will be looking at the ecological effects of elodea on various fish and invertebrate communities.
By Kate Mohatt, Ecologist, Chugach National Forest