Blue carbon: Port of Seattle’s kelp, eelgrass and shellfish enhancement pilot project

The Port of Seattle is working to become carbon neutral by 2050. In addition to reducing emissions, the Port’s strategy includes enhancing carbon sequestration through habitat restoration. To that end, the Port completed a study in 2017 to quantify sequestration benefits associated with different land cover and habitat types found in the Duwamish River estuary and Elliott Bay, including riparian forest, marsh, mudflat, eelgrass and kelp beds. The review determined that kelp and eelgrass – so called “blue carbon” – provide highly significant sequestration benefits. In fact, they sequester more carbon than almost any other habitat type in the world. As a function of removing CO2 , they may also provide ocean acidification refugia for pH sensitive species like shellfish and corals. To explore this potential, the Port is partnering with the Puget Sound Restoration Fund and will be undertaking a 25 acre kelp, eelgrass and shellfish enhancement pilot study at Smith Cove, Seattle. The project will create 8 acres of canopy kelp forest, 12 acres of eelgrass, and 5 acres of experimental shellfish plots. Monitoring will be conducted over time to assess the project’s effects on water quality, habitat, and carbon sequestration. Challenges include that the project site is within an active area that supports important maritime land uses: a cruise ship terminal, commercial vessel moorage, recreational boating and shoreline public access. As such a high level of effort with respect to pre-project environmental impact assessment, public outreach, and permitting is anticipated