Tomales Bay Seagrass Protection

High concentrations of fish are found in eelgrass habitat for several reasons: it provides abundant food sources (including algae, fish, invertebrates, and detritus); it provides a hiding space for many species of fish, protecting them from predation by larger fish and birds; and eelgrass beds serve as an important nursery ground, providing a safer place for larvae and juvenile fish to feed and grow.  Moreover, some species of fish use eelgrass beds for their spawning grounds, including the commercially important Pacific herring, which relies on abundant eelgrass beds to support its roe.  Other commercially valuable species feed in eelgrass beds at some point in their lives as well, including Dungeness crabs, rockfish, salmon and Pacific herring.

Eelgrass beds also help to support a very large population of birds on Tomales Bay, which feed on eelgrass, fish, and invertebrates in the beds and adjacent areas. In addition to supporting fish and birds, eelgrass sustains a myriad of invertebrate species: clams, shrimp, snails, nudibranchs, amphipods, worms, and bryozoans consume tiny algae that grow on eelgrass blades and filter detritus and phytoplankton from the water.  In turn, these animals provide food for many other animals that live and/or feed in eelgrass beds.

Eelgrass provides ecosystem services beyond providing habitat and food for animals.  It improves water quality along the coast by trapping sediments and reducing excess nutrients and pollutants in the water column. In some cases eelgrass beds can also help to prevent coastal erosion by buffering the impacts of wave energy and storms. Currently Tomales Bay is being studied for potential benefits of eelgrass beds to sequestering carbon.

Because of their ecological importance and vulnerability to impacts from humans, eelgrass beds are protected in several different ways: they are designated as “special aquatic sites” under Section 404(b)(1) Guidelines of the Clean Water Act; designated as Essential Fish Habitat under the Magnuson-Stevens Fishery Conservation Management Act; and protected under California Department of Fish and Wildlife regulations.  Moreover, GFNMS regulations offer protection through prohibiting vessel anchoring within Tomales Bay Seagrass Protection Zones.

Help Protect Seagrass

The Sanctuary has taken several actions to protect seagrass, and we need your help to keep it protected.  If you are planning on boating, kayaking, swimming or wading in the nearshore waters of Tomales Bay, then avoid certain actions that can impact seagrass beds. Best practices include:

• If you are kayaking and want to beach your boat, choose a location that is free of seagrass.
• When swimming or wading, be sure not to step in seagrass.
• Before anchoring, check for seagrass.  If you see it, move to another location or further offshore.  Eelgrass in Tomales Bay (Zostera marina) is generally found in depths less than 20 feet. Without exception, anchoring is prohibited in Seagrass Protection Zones.

Seagrass Protection Zones

Seagrass in the Sanctuary is defined as any species of marine angiosperms (flowering plants) that inhabit portions of the seabed in the Sanctuary.  There are a total of seven no anchoring zones, which comprise 22% of the surface area of Tomales Bay. The location and extent of the no-anchoring zones encompass the majority of seagrass coverage within the jurisdiction of the Sanctuary and are based upon seagrass data provided by California Department of Fish and Wildlife from 1992, 2000, 2001 and 2002. The no-anchoring seagrass protection zones include some areas where seagrass coverage is extensive and other areas where coverage is discontinuous and patchy. All zones extend shoreward to the Mean High Water Line. This prohibition protects seagrass beds in Tomales Bay from harm from anchoring. View the map and coordinates (PDF, 2.5 MB) of the designated no-anchoring seagrass protection zones.