January 19, 2022

Marine Floating Wetlands

Project Background

To test the viability of floating wetlands in marine waters, the GFL and EarthCorps have installed customized BioMatrix eco-islands along a dock at Shilshole Bay Marina. The living shoreline units are again aimed at providing missing habitat for fish and to begin to restore wetland functions along urbanized shorelines where traditional restoration is not possible. We filled the Biomatrix units with our custom-designed substrate mix – half which contains biochar – and planted them with a carefully selected plant palette based on observations of Puget Sound shorelines. Two of the ten connected units are submerged and planted with eelgrass to provide fish refuge. The floating wetlands are located between the dock and the steep rip-rapped shoreline next to a stormwater outfall, with visibility from the marina walkway above. We are monitoring them for fish use and behavior, plant survival and health, and potential water quality benefits.

Honda Marine Foundation provided a grant to EarthCorps to purchase and install the BioMatrix units, and GFL design and research is funded by King County Waterworks from Councilmember Jeanne Kohl-Welles, with site support from the Port of Seattle. We have begun research on plant performance, and on-site stewards are generously contributing their time to watch over and irrigate the wetlands. Head out to Shilshole Bay Marina to see them for yourself!