Giving Tree of the Sea: Eelgrass

Learn about how this humble grass is a linchpin in Bay ecosystems and why it's worth preserving.

Common eelgrass (Zostera marina) is found in estuaries and bays of Point Reyes, Tomales Bay, and Limantour. The perennial sea grass can be identified by its occasional flowering and its long, thin green leaves which can reach up to 1 meter long. Common eelgrass provides home and food to a variety of aquatic life including many snails, sea stars, anemones, crabs, clams, and fish species. Not only does this eelgrass support a vast quantity of marine life, its dense growth along the seafloor traps sediment and substrate — a crucial factor in preventing coastal erosion.

Because the abundance of life and seabed integrity common eelgrass supports, it is vital that its population continues to thrive. Unfortunately, in recent years, human interaction has led to decreases in the population of this essential subtidal plant species. In particular, we have dredged the ocean’s substrate in order to increase the depth and navigability of ports and other waterways. This has directly cleared and stripped the seabeds where eelgrass (along with numerous other aquatic plants) thrives. Water pollution, bioaccumulation of chemicals, eutrophication from runoff, and increased ocean temperatures have also led to direct and indirect stunts in the growth of common eelgrass. Given the frequency of coastal development and pollution in the Bay Area, acknowledging the significance of this species, as well as understanding the factors that pose threats to it, becomes crucial in the collective endeavor to restore the health of our bay ecosystems.

Eelgrass is a notoriously difficult species to restore. Local native plant nurseries do not commonly grow this subtidal grass so restoration practitioners need to collect shoots or seeds from nearby beds. Once materials are collected, restoration practitioners will go out into the bay with wetsuits, and occasionally scuba diving gear, to transplant the shoots or seeds directly into the sediment. Because of how difficult this process is, eelgrass restoration projects are more expensive compared to traditional, land-based habitat restoration projects. Moreover, eelgrass is a difficult plant to establish. One study that evaluated eelgrass restoration projects along the coasts of Washington, Oregon, and California found that only 51-58% of eelgrass restoration projects were defined as successful by the final monitoring period.

Before restoration practitioners spend time, money, and resources on eelgrass restoration, they would likely benefit from knowing the best locations to plant around the bay that has the highest chance of restoration success. With a grant provided by the California Ocean Protection Council, Audubon California, Merkel & Associates, Inc., and Katharyn Boyer have developed a model to provide that information. The San Francisco Bay Eelgrass Habitat Suitability Model was created to provide insight on locations within the bay that are the most suitable for eelgrass restoration and have site conditions that give the newly transported eelgrass shoots the highest chances of survival. This project also encompasses a model variant that incorporates environmental data reflecting potential future conditions resulting from climate change. Utilizing historical data on eelgrass distribution in San Francisco Bay, along with factors such as light availability, salinity, current velocity, and temperature, the eelgrass habitat suitability model forecasts the suitability of habitats across the entire bay area. This model is a great tool for restoration practitioners, conservation professionals, resource managers, and environmental consultants.

With additional funding, the team plans to expand the model into four other major bays across California that support major eelgrass beds: Humboldt Bay, San Diego Bay, Mission Bay, and Tomales Bay.

Unless you have access to a scuba suit and marine plant sampling equipment, it might prove somewhat challenging to directly restore this plant. However, there are still three main ways that you can help resuscitate this declining eelgrass population. 

  • Raising awareness through social media about this environmental issue (like linking this article in a post), is a simple, easy, and effective place to start. 
  • Embracing eco-conscious practices in your own home: 
    1. Structures built over shoreline prevent sunlight from reaching the eelgrass, stunting its growth, so refrain from developing any structures that would otherwise cause this to happen. 
    2. Most fertilizers and other plant-nourishers contain chemicals that induce rapid plant growth. These chemicals can leach into creeks and other bodies of water that flow into the bay and can cause algal blooms that block out sunlight and deoxygenate the water, harming wildlife and underwater plant species in the ecosystem. You can help stop this issue by refraining from using fertilizers and/or by observing and preventing how your fertilizers might escape your garden. Investing in at-home compost and natural fertilizers can help mitigate this issue while reducing food waste.
  • If you want to assist in a more direct impact: 
    1. Participate in local volunteer events where you can help plant eelgrass, monitor growth, and collect data. 
    2. Support environmental organizations in the community that are deliberately working towards ecosystem restoration. San Francisco Bay National Estuarine Research Reserve and Richardson Bay Audubon are part of ongoing efforts to develop suitable habitat for eelgrass and preserve existing eelgrass beds in the Bay. 

How you can help, right now