Elodea
Elodea spp.
Also known as Common or Canadian waterweed, elodea is a submerged perennial aquatic plant that has the potential to form large mats in lakes, ponds, and slower moving waterbodies. Several very similar species of elodea are currently known to be present in Alaskan waters.
Elodea only reproduces vegetatively in Alaska and has yet to be observed to produce seeds. In its natural range it can produce small white flowers and seeds for reproduction.
In Alaska, elodea has been known to remain green throughout the winter and experience little to no die off so it is occasionally encountered while ice fishing.
Identification
Elodea can be readily identified form native species with a few characteristics. The primary identifying feature is that the leaves grow in whorls of three up the stem. No other aquatic plant in Alaska grows this way so its a safe identifying feature to use.
Elodea tends not to grow beyond a 3/4 inch diameter and from the surface, can look a bit like a spruce bough submerged in the water. Other key features include that it is a floating, rooted, aquatic plant and does not emerge out of the water like some other similar looking species. When submerged, elodea can sometimes appear to be frosty or reflective compared to other plants but often times is not distinctly colored. Once removed from the water it can be a bright and almost artificial looking shade of green.
Elodea can also be seen washed up on shore in heavily infested waterbodies and retains most of its shape which aids in shoreline identification.
Elodea in Alaska
Elodea was a popular plant used in fish tanks and was accidentally introduced to Alaskan waters through the banned practice of aquarium dumping. The first establishment was recorded in Cordova in 1982, and again in 2010 in the regions around Fairbanks and Anchorage. Elodea was banned from the aquarium trade in Alaska in 2014.
There are currently elodea infestations in and around Fairbanks, the Susitna River area, Anchorage, the Kenai Peninsula, and the Copper River region. The National Park Service has a good summary of elodea presence and history in Alaska.
Invasiveness
Elodea has been identified as a noxious, invasive weed in Alaska and can spread between water bodies via movement of boats, float planes, and other human activity. A single fragment of the plant in an infested water body has the potential to travel great distances and start a new infestation.
Once established, elodea can alter aquatic habitats by reducing water velocity, increase sedimentation, decreasing food resources for most aquatic organisms, and can even overtake the entire surface area of a body of water.
Control Methods
Because elodea can reproduce vegetatively via fragments, it is generally ineffective to remove it with mechanical means such as raking or dredging. Physical removal may also cause it to spread to other connected waterbodies.
Aquatic herbicides are currently the best and most ecologically sound method for eradicating elodea from a waterbody. Systemic herbicides that target both the vegetation as well as the roots are most effective.
