Walking the shallow shores of Henderson Inlet in the summer is the treat of a lifetime, though it means managing the slippery strands of seaweed that cling to your ankles and catch between your toes. If some of the strands are green, thin, and long, it is an especially lucky day. It means the wondrous world of eelgrass is growing in the water nearby. Eelgrass may be small, only about ¼” wide, but it’s a big deal.
What is eelgrass?
Puget Sound’s native eelgrass (Zostera marina) is a plant, not a seaweed, that gets its name from its long, narrow leaves, shaped like the bodies of eels. It lives on the very low shore, down to as much as 20 feet deep. Zostera marina is commonly found on the coasts of the North Pacific, the North Atlantic, and Eurasia and is one of 15 species of Zostera worldwide (“Zostera.” Wikipedia, 2022).
This underwater grass-like perennial plant grows in meadows with leaves about ¼” wide and often one to three feet long. Eelgrass is common in tidelands and shallow waters along Puget Sound’s shoreline (Gaeckel et al. 2009). It spreads by underground rhizomes and also produces small white flowers, which make seeds. It is one of very few true plants that live in the sea and is extremely important ecologically (Hemminga and Duarte 2000).
Eelgrass grows at Meyer’s Point Environmental Field Station on the west shore of the inlet (https://cas.wsu.edu/2019/06/10/a-point-of-reference/), and likely in other parts too, though our area of Puget Sound has no current state survey sites. https://wadnr.maps.arcgis.com/apps/webappviewer/index.html?id=83b8389234454abc8725827b49272a31
NOAA and many other scientific organizations recognize eelgrass meadows as among nature’s most diverse and productive ecosystems. Primarily, eelgrass protects our shores from erosion, provides habitat for marine life and food for migratory birds, and mitigates climate change with its nutrient cycling and carbon storage capabilities. It’s been said that eelgrass is more effective at storing and collecting carbon than trees (Hurlimann 2019).
Eelgrass reduces shoreline erosion. When it comes to erosion protection, eelgrass meadows trap sediment, reduce the force of wave energy, and help stabilize the substrate. This is due, in part, to the way that eelgrass forms beds across the seafloor and anchors itself firmly in place. Its roots and rhizomes tie down sediments while the leaves, which stand up when submerged, help slow the water and calm loose debris such as sand and silt arriving on incoming tides. In these ways, eelgrass is a stabilizing force in reducing erosion and protecting shorelines (Duarte 2002).
Eelgrass provides habitat.
Eelgrass creates a mostly underwater ecosystem that supports marine life phenomenally well. Its extensive root structure that holds the soft and sandy seafloor teams with life. Eelgrass leaves, too, provide vital food and habitat for wildlife such as finfish, shellfish, birds, otters, and other creatures. The floating leaves allow attachment sites for tiny organisms while sheltering zooplankton, the small crustaceans that juvenile fish and other organisms eat. By protecting the young fish and the invertebrates they rely on, eelgrass affects everyone all the way up the food chain.
Eelgrass meadows create a structurally complex habitat for a suite of species. They offer fish and crabs cover when they’re young. Of particular interest to current efforts to restore native salmonid populations, eelgrass has been designated an “Essential Fish Habitat” for juvenile salmonids (Gibsons 2017). The meadows are hatcheries for eggs, nurseries for salmonids, foraging grounds for sea stars, leaf slugs, and crabs, and spawning grounds for fish like Pacific Herring and Plainfin Midshipmen. They are also a food source for certain migratory waterfowl. We can say that eelgrass meadows are vital to animals that live both above and below the ocean’s surface. (Simenstad 1984, Heck et al. 2003).
Eelgrass helps mitigate climate change.
Eelgrass is good for water quality and stores greenhouse gasses like carbon dioxide, so it’s believed to be a frontline defense against climate change.
Eelgrass plays an important role in making the water clear by trapping nutrients that run off from land. It filters out polluted runoff. It improves water clarity also by reducing turbidity. Clearer water allows better photosynthesis in its leaves, as it produces oxygen while eliminating excess nutrients.
When it comes to carbon sequestration, seagrasses play an important role worldwide. They can be a natural carbon sink, removing carbon dioxide from the air and storing it in sediments, sometimes for thousands of years (Baltes, 2016). Coastal seagrass habitats possibly store more carbon per acre than tropical rainforests.
All in all, eelgrass is yet another component of Henderson Inlet to celebrate, foster, and protect as we come together to ensure the health and variety of Henderson Inlet for generations to come.
Baltes, K. (2016, February 19). Green Eelgrass, Blue Carbon; Understanding the role of eelgrass in climate change. MIT Sea Grant. Green Eelgrass, Blue Carbon (noaa.gov)
Duarte, C. M. 2002. The future of seagrass meadows. Environmental Conservation 29:192-206.
Gibsons Eelgrass Fact Sheet. 2017. tidesA13_eelgrassfacts (gibsons.ca)
Gaeckle, J. L., P. Dowty, H. Berry, and L. Ferrier. 2009. Puget Sound Submerged Vegetation Monitoring Project: 2008 Monitoring Report, Nearshore Habitat Program. Washington State Department of Natural Resources, Olympia, WA.
Hemminga, M. A., and C. M. Duarte. 2000. Seagrass Ecology. Cambridge University Press, Cambridge, UK; New York, NY.
Hurlimann, S. (2019, July 4). How Kept Naturally Combats Global Climate Change. Science in the News. How Kelp Naturally Combats Global Climate Change – Science in the News (harvard.edu)
Zostera. (2022, November 20). In Wikipedia. https://en.wikipedia.org/wiki/Zostera