Populations of a tenacious weed, once a popular aquarium plant, called Brazilian elodea, have exploded in the Chehalis River this summer. Since finding it in the Chehalis River in 1998, Thurston County, Washington Department of Natural Resources and the Chehalis Tribe have removed over 86,000 pounds of the invasive plant. 34,840 pounds have been removed since August 1.
Brazilian elodea is native to South America and is imported to the US as an aquarium plant (often sold under the name Anacharis). Rooting in water up to 20 feet deep, the plant forms dense mats of stems and leaves on the surface that affect water movement, water quality, recreation and boat navigation. It can trap large amounts of sediment that will cause increased flooding and make detrimental changes to native fish and plant habitat.
Kathy Hamel, an aquatic plant specialist with the Washington Department of Ecology is particularly worried about Brazilian elodea in the Chehalis River. "Its dense growth can block salmon passage and create low oxygen and high pH. These conditions are not conducive to the health of water quality or sensitive fish like salmon".
The plant is spread by fragmentation. Roots form on every tenth node of the stems, creating new plants that break free, float down stream and start new infestations.
MAJOR REMOVAL EFFORTS PLANNED – During the week of September 11, a full barrage of control methods will be used: crews of people will hand pull the weed, followed by the Chehalis Tribe and contractor Doug Freeland, using diver (or suction) dredging.
Diver dredging vacuums the plant material out of the river after the roots have been dislodged by divers. The purpose of diver dredging is to effectively remove all of the plant biomass, including the roots. The water is returned to the river and the plant material is disposed of.
The Brazilian Elodea Removal Project is led by Thurston County Noxious Weed Control. The majority of the funding for the project has come from the U. S. Fish and Wildlife Service, The Chehalis Tribe, Washington Department of Natural Resources, and Thurston County. Since the inception of the project three years ago, over $171,700 has been spent.
A 9-minute DVD produced by Thurston County TV (TCTV), entitled "All choked up," is available to interested groups.