California Department of Fish and Wildlife

Humboldt Bay Cooperative Eelgrass Project

Native eelgrass, Zostera marina, in Humboldt Bay. Photo courtesy of Annie Eicher/UC ANR.

The Humboldt Bay Cooperative Eelgrass Project is a collaborative project involving the CDFW, U.C. Sea Grant, Humboldt State University, and the Humboldt Bay Harbor District. Since 2001, this team has been surveying and monitoring the native eelgrass, Zostera marina, at 15 randomly selected points in Humboldt Bay. Each summer, project collaborators measure each site for plant size, density and total above ground biomass by collecting vegetative material from the site. In addition to the 15 random sites, two transects are surveyed quarterly at the foot of Washington Street in Eureka; eelgrass shoots are measured and counted at this site though no plant material is removed. The results are shared among collaborators and resource managers, and project outreach includes numerous presentations to local groups.

This project also coordinates with SeagrassNet, an international seagrass monitoring project based out of the University of New Hampshire. SeagrassNet monitors changes in seagrass populations in 43 locations worldwide. Humboldt Bay is the most recent addition to this network with two permanent transects, one in Arcata Bay and one in South Bay. Surveys are conducted quarterly with the first held in July 2007. Surveys collect data on percent cover, plant density, total plant biomass, canopy height, and water salinity. A core sediment sample is also collected along with a photographic record of the site. Seagrass "voucher" specimens collected during the core sediment sample are sent to the Smithsonian for preservation and storage. This study is scheduled to go on indefinitely. This is the first SeagrassNet site in California, and the third on the entire West Coast of the Americas.

Blades of dwarf eelgrass, Zostera japonica, compared to native eelgrass, Zostera marina. Photo courtesy of Annie Eicher/UC ANR.

Dwarf eelgrass, Zostera japonica, was discovered in Humboldt Bay in June 2002 during the annual native eelgrass survey conducted by the Humboldt Bay Cooperative Eelgrass Project. The detection of dwarf eelgrass in Humboldt Bay represents the southern extent of its range in the Eastern Pacific, and it is the first time this introduced species has been encountered in California. Dwarf eelgrass is a non-native, invasive eelgrass that rapidly colonizes non-vegetated mudflats, physically altering native habitat and negatively impacting native species. Dwarf eelgrass can be distinguished from the native eelgrass, Zostera marina, by its very narrow blades After the discovery of dwarf eelgrass, a team of state and local scientists was assembled to assess the available information on this invasive and the extent of its introduction into Humboldt Bay. It was the consensus of the team and other marine scientists that an eradication program should be undertaken. Eradication efforts were initiated in April 2003 by a team of volunteers coordinated by U.C. Sea Grant in collaboration with the CDFW. Since April 2004, a team of scientists, students, and volunteers have been annually monitoring and eradicating all known occurrences of dwarf eelgrass in Humboldt Bay.

Kirsten Ramey, Associate Marine Biologist
Phone: (707) 445-5365

More Information
Invasive Species Program