Teams of scientists from the Aquatic Division of the Washington State Department of Natural Resources took advantage of this summer’s minus tides to conduct continuing research on large-scale efforts to re-establish native eelgrass (Zostera marina) in the waters off Joemma Beach State Park.
“This is by far one of our most successful sites,” said Dr. Jeffrey Gaeckle, a sea grass ecologist who leads the Eelgrass Stressor Response for DNR. “In 2015, two areas at Joemma Beach were transplanted with native eelgrass harvested from healthy donor sites near Rocky Bay and the Nisqually Delta,” he said. Two years later, monitoring showed an increase in shoot density up to five times the number of shoots transplanted. The vegetative area doubled from the original area planted.
In 2016, a third transplant method was applied by the environmental consulting firm Hart Crowser that consisted of weaving donor eelgrass shoots into burlap strips secured with long staples into the substrate below the water surface. The burlap strip method attempts to emulate an intact eelgrass rhizome matte to resolve challenges presented by burrowing shrimp. (KP News, September 2016)
Long recognized as problematic to the shellfish industry, burrowing shrimp stir up the substrate, causing commercially grown oysters to sink and preventing eelgrass from taking root in the constantly shifting sand. “You can be walking along on firm sand and then suddenly step into a very soft spot; that’s the work of burrowing shrimp,” Gaeckle said.
“We are currently conducting a method study to determine the best techniques for successful transplanting using the most efficient and economical methods possible,” he said. “The burlap is very effective against burrowing shrimp because they come up and hit their heads on the burlap, however with the burlap there is also more surface for algae to stick and grow.” Algae compete with eelgrass for nutrients, light and space.
Native eelgrass is the predominant sea grass in Puget Sound, yet it remains nearly absent from the submerged shorelines along the Key Peninsula. DNR aquatic scientists are simultaneously studying potential causes of this relative absence as they continue working toward the goal set in 2011 by the Puget Sound Partnership targeting a 20 percent Soundwide increase in eelgrass by the year 2020. “We knew we couldn’t plant our way to that goal, so we focused on building a model that would identify sites throughout Puget Sound that were suitable for eelgrass restoration,” Gaeckle said.
Eelgrass occupies a fairly narrow range of depths, ideally ranging from plus 1.4 meters down to minus 11 meters relative to the average mean low water height. “Much deeper and the eelgrass doesn’t get enough light,” Gaeckle said. “Too much exposure at the lowest tides on hot summer days stresses plants. The eelgrass rhizomes need to store enough carbohydrates during the summer months to see them through the low light of winter.” Eelgrass grows anywhere from 16 inches up to six and a half feet tall.
Recently published work based on research by the National Oceanic and Atmospheric Administration, the University of Washington and Washington Department of Fish and Wildlife suggests eelgrass has been stable in Puget Sound for the last 40 years. A recently released report by DNR on the Puget Sound sea grass monitoring program for 2015 demonstrated that while some areas of Puget Sound enjoy vibrant expansion of eelgrass meadows, other less fortunate areas in the Sound are in serious decline, suggesting eelgrass ecosystems present very localized challenges to restoration.
Worldwide, eelgrass is in decline. Gaeckle said the scientific lessons learned at Joemma Beach may well influence future restoration efforts far beyond the shores of the Key Peninsula.
For more information, go to www.keypennews.com/joemma-beach-eelgrass.