JUNEAU — The Department of Fish and Game, in cooperation with the City and Borough of Juneau and the Alaska Department of Transportation & Public Facilities, is planning to introduce seawater into Twin Lakes as a means of inhibiting the overgrowth of aquatic plants.
One of the primary purposes of the project is to restore fishing opportunity along the lake shoreline while at the same time reducing the overgrowth of aquatic plants in the lake to improve boating and swimming experiences.
According to a release from ADF&G, high productivity of aquatic plants is common in shallow lakes and especially in urban settings where nutrient loading can occur. If left untreated, these conditions usually worsen and can severely impact water quality.
A significant reduction of aquatic plants in Twin Lakes was observed for several years immediately following the year 2000 when the lake was drained for maintenance purposes.
While exposure to air and freezing temperatures were partially responsible for reducing plant growth at that time, the higher salinity produced in the lake was also likely a factor.
In the spring of 2010, the salinity in Twin Lakes was raised to levels known to inhibit growth of the plants present in the lake. Raising the salinity of the lake was accomplished through tidal exchanges that repeatedly drained and refilled the lake with seawater. The normal lake level was restored by closing the gate valves after a series of high tides that occurred near the end of March. This project was successful at inhibiting and delaying the growth of aquatic plants for most of the summer months, and therefore additional treatment with salt water is planned for this spring from mid-April to mid-May.
During the saltwater treatment, attempts will be made to prevent stocked fish in the lake from migrating to the ocean. Stocking of additional hatchery raised king salmon will occur as usual in early June just prior to the ADF&G Family Fishing Day event.
For more information about this project call the Douglas office at 465-4270.