David Shull, Western Washington University, Shannon Point Marine Center
Denise Crowe, Western Washington University, Shannon Point Marine Center
Jennifer Ruesink, University of Washington, Department of Biology
Sandy Wyllie-Echeverria, University of Washington, Friday Harbor Laboratories
Sylvia Yang, Western Washington University, Shannon Point Marine Center
Eelgrass is an ecologically, economically, and culturally important resource that also serves as an indicator of the health of Puget Sound’s estuaries. The Puget Sound Partnership seeks to expand Puget Sound eelgrass acreage by 20 percent by the year 2020. Porewater sulfide may play a role in limiting the distribution of eelgrass. This study will survey two sites to understand the relationship between eelgrass abundance and sediment porewater sulfide; data collected will be used to model the effects of sulfide on eelgrass population dynamics. Results will assist the development of restoration strategies for this significant species in Puget Sound.
The Washington Sea Grant-supported research team set out to identify the naturally occurring relationship between eelgrass distribution and sediment pore water sulfide concentration. Investigators tracked tolerance limits of different eelgrass life stages to various levels of sulfide, light and water column-dissolved oxygen. The goal was to determine how much eelgrass ameliorates sediment sulfide conditions and to predict eelgrass population trajectories, given different sulfide conditions and restoration strategies.
The researchers concluded that eelgrass growth and photosynthetic efficiency is reduced in the presence of high sulfide concentration, but it requires multiple stressors before eelgrass is negatively impacted. They constructed diffusive gradient thin-film (DGT) sensors that provided better measurement of sulfide and its distribution in sediment pore water. They also constructed tanks that could be filled with eelgrass, sediment and the DGT sensors for testing. In the field, researchers observed higher sulfide concentrations near eelgrass leaves than near eelgrass root systems, which explained the variable distribution of sulfide in the sediment.