Grand Mound, Washington - A large and damaging infestation of Brazilian Elodea, an aquatic plant native to South America previously sold for use in aquariums, has finally been controlled in the Chehalis River after ten years of sustained effort. A large area of infestation has been reduced by 77%. Although continued monitoring and control will be necessary, the removal of the bulk of the infestation has substantially improved water quality and eliminated Brazilian elodea's impacts on water temperature, water flow, and dissolved oxygen available to salmon.
The likely source of the Brazilian elodea infestation was Plummer Lake in Centralia . It is suspected that someone dumped an aquarium into the lake.
Brazilian elodea is a robust, fast-growing plant that began to choke the river, raising the water temperature, holding back sediment, reducing dissolved oxygen levels, and creating shallower water.
In Thurston County , the Noxious Weed Control Board began removing individual Brazilian elodea plants from the Chehalis River in 1999. By 2003, the infestation was so large that individual hand removal was no longer practical.
Since then, a growing network of County Weed Boards, state and federal agencies and Tribal Government have collaborated to remove Brazilian elodea from the river. Funders and collaborators included the state Department of Natural Resources, the U. S. Fish and Wildlife Service, the Chehalis Tribe, the state Department of Ecology, the state Salmon Recovery Funding Board, and the Nature Conservancy.
Over time, repeated annual surveying and removal of Brazilian elodea have reduced its prevalence. At its height, the scale of the infestation required sending divers into the lake to vacuum it up and dislodge its roots. In 2007, More than 106,000 pounds of Brazilian elodea was removed from the river; in 2009, the amount had been reduced to 25,693 pounds.
"This is a saga that teaches several lessons," says Thurston County Noxious Weed Board chair Gene Little. "It's a lesson about how just one thoughtless action, like dumping an aquarium in a lake, can harm an entire river system. We need to educate citizens to avoid spreading invasive species like this. But there's also a very positive lesson about how, when government agencies, tribes, and non-profit citizens organizations collaborate, we can make things right in our rivers and our environment."
For a brochure, video, and statistics about the Brazilian elodea removal project, go to http://www.co.thurston.wa.us/tcweeds/special-projects.htm