MILFOIL
E. watermilfoil forms thick mats in shallow areas of a lake blocking sunlight and killing off native aquatic plants that fish and other underwater species rely on for food and shelter. The USDA classifies it as an invasive species, and is considered a “noxious weed” to both Union Bay and Washington State.
HISTORY
Before SUBA’s founding in 1975, Eurasian watermilfoil (Myriophyllum spicatum) choked areas in both Union Bay and surrounding waters. Legend has it that the UW crew coach was so upset with the milfoil impeding crew practices that, for a cup of coffee, he would harvest milfoil on Saturday mornings throughout Union Bay.
At the time, King County provided milfoil control. They used a mechanical harvester to cut E. milfoil and pile it in the bin on the harvester. It was then dumped on the shoreline, raked and removed. By 1990, however, research revealed that Eurasian watermilfoil reproduces when plant fragments settle to the bottom and form roots. Harvesting was quickly stopped, and with no other control methods permitted within city limits, the milfoil reproduced exponentially.
RESEARCH
Between 1990 and 2010 SUBA evaluated and researched many different techniques to control milfoil and improve water quality, which included bottom barriers, E. milfoil weevils, hand pulling, diver-assisted suctioning, and solar powered aerators. None of these methods were found to be effective in such a large body of water though.
By 2002, King County developed a Regional Eurasian Milfoil Control Plan. With an eventual change in Seattle’s aquatic policy and assistance from the Washington State Department of Ecology (WSDOE), SUBA partnered with Seattle Public Utilities and the University of Washington (UW) in applying for a planning grant in 2009, which was approved in 2010.
PLANNING
The first step, a one-year planning grant from the WSDOE, enabled us to form a Steering Committee and create an Integrative Aquatic Vegetation Management Plan (IAVMP). By 2012, we received a three-year Implementation grant to implement the steps described in our 10-year IAVMP.
The UW Athletic Department and SUBA are continuing to follow the plan, revised in 2013. In 2015, we received another implementation grant to provide funding for years 4-5 of the IAVMP.
Since then, SUBA and the UW have co-funded the invasive plant management program. SUBA monitors all invasive aquatic plants including E. Milfoil, Brazilian elodea, curly leaved pondweed, and fragrant white waterlilies and holds an annual fund-raising drive to cover 50% of the costs of treatment. UW funds the project from the Athletics program, the Waterfront Activities Center, and mitigation from the Husky Ditch Project.
PROGRESS
We partner with Aquatechnex in invasive weed species management. Every spring, Aquatechnex performs an aquatic plant survey to determine density of invasive and native aquatic plants. Based on the results of this survey and on best practices recommended by WSDOE, they then develop a plan for aquatic weed management during the summer. At the end of the summer, another survey is conducted to evaluate plan effectiveness.
Because E. milfoil and other invasive aquatic plants are now well controlled, only the shallow waters in which weed growth limit wildlife and human activity are treated. These areas include a practice area mid-lake for the UW crew as well as an area extending out about 100 feet from the west and north shoreline. The south and east boundaries of our E. milfoil management are the deep waters of Lake Washington and the shipping lane through Union Bay.
Results of the annual treatment and recommendations for the following year are reported to SUBA members in a newsletter and during our annual public meeting in November.
RESOURCES
Guide to Aquatic Weeds in King County
King County Noxious Weed Control Board
Washington State Rules for Aquatic Plant Removal and Control