No matter where you live, chances are you and your family are benefiting from eelgrass. This beautiful plant found in many of California's bays and estuaries provides dozens of ecosystem services and provides essential habitat for coastal birds and other wildlife.
What is Eelgrass?
Eelgrass on the U.S. West Coast is a member of the family of sea grasses called Zosteraceae and belongs to the higher taxonomic group of flowering plants called angisosperms. This sea grass grows submerged or partially floating in the marine environment. It reproduces through rhizome growth and seed germination. The blades of eelgrass are similar to those found in common grass species and depending on the zone, these could grow up to 4 feet in length. Eelgrass beds grow rapidly in the spring and summer, then decompose in the fall and winter. Dead eelgrass blades often wash up on the beach where their decay adds crucial nutrients to coastal environments.
Which Animals Rely on Eelgrass?
As a crucial nursery habitat for crabs, salmon, and other wildlife, eelgrass boosts the economies of our coastal communities through fisheries and tourism. Healthy eelgrass beds also clean and filter water, absorb climate-warming carbon, and act as natural buffers to protect the coastline during storms.
Eelgrass provides habitat and food for many marine species. Some waterfowl, such as Brandt eat the leaves directly. Algae and invertebrate species use the eelgrass blades as substrate and some grow as epiphytes on the surface of the leaves. Eelgrass supports a large number of grazing crustaceans such as amphipods, crabs, and shrimp. Bacteria, fungus, and detritus (dead animal and plant matter) can also form a brown coating on dead leaves, which then provides food for small invertebrates.
Pacific Herring are dependent on eelgrass for spawning. They lay eggs on eelgrass leaves and their young are protected within the eelgrass as they mature. During low tides, on tideflats, eelgrass beds hold moisture like a sponge, offering a safe, wet habitat for small creatures. With their extensive, intertwined root mats, eelgrass preserves the highly productive bacteria in the sediments which nourish many invertebrates by holding sediments in place and pumping oxygen below the muddy surface.
Why is Richardson Bay Important for Eelgrass?
Within San Francisco Estuary, Richardson Bay stands out as a particularly unique location for eelgrass restoration. A model of environmental conditions in the estuary has identified Richardson Bay as the area with the greatest area suitable for restoration (Merkel and Associates 2004). Hence, Richardson Bay is highly valued both for its existing eelgrass resources and its potential for restoration.
Richardson Bay is critically important to tens of thousands of diving ducks, grebes, and other waterbirds who rely on the bay for roosting and feeding each winter. During the winter months, Richardson Bay teems with Surf Scoters, Lesser and Greater Scaup, Western and Horned Grebes, Double-crested Cormorants, and other birds. Richardson Bay is also well known for its annual winter herring runs which are an important local fishery and provide important food for wintering birds. There is concern that the long-term decline in bird numbers and herring in Richardson Bay and other parts of San Francisco Bay is linked to the decline in native eelgrass beds.
Threats to eelgrass include habitat alteration and recreational, industrial, commercial, and residential development that impacts the shallow protected bays and estuaries required for eelgrass growth. Some of the major impacts include:
- Dredging can destroy eelgrass beds either directly or indirectly by reducing light penetration
- Upland erosion and construction activities can increase sedimentation which can smother eelgrass.
- Shoreline structures built over the water prevent eelgrass from getting enough light for growth.
- Excessive nutrients can accelerate harmful algae growth on eelgrass blades, blocking out light.
Restoration of eelgrass involves transplanting mature plants or seeds taken from healthy donor beds to a restoration site, once suitable environmental conditions have been established for eelgrass survival. Transplanting adult plants involves planting the individual units by hand or by tying eelgrass to transplant frames called TERF’s (Transplanting Eelgrass Remotely with Frames, developed by Fred Short, University of New Hampshire).