By Adam Weaver, Wild Oysters Intern
Eelgrass populations are dwindling in the San Francisco Bay. But why should you care about a marine plant named after a creepy snake-like fish? Eelgrass is a foundational species for the San Francisco Bay and supports much of the biodiversity in the bay ecosystem. The underwater flower, or marine angiosperm, grows on muddy and sandy bottoms in the shallow subtidal areas of the bay, providing food and habitat for a variety of species. Waterfowl and snails eat eelgrass, certain invertebrates and algae use the plant’s blades as a substrate, the grass serves as a nursery and shelter for fish reproduction, and bacteria, fungus, and other organic matter form a brown coating on eelgrass, providing food for small invertebrates and crustaceans like amphipods, crab, and shrimp. Even river otters are beneficiaries of the habitat formed by eelgrass.
Another increasingly important ecosystem service of eelgrass is the way in which it can combat climate change effects. Beds of eelgrass reduce wave energy, which lessens erosion and sediment buildup that cause rising water levels. Mitigating erosion also protects species in their developing stages, such as bivalves like the Olympia Oyster, California Mussel, and other mollusks. In the absence of eelgrass, higher turbulence in the water makes it exceedingly difficult for invertebrates to survive as free swimming larvae. If Olympia Oysters, another ecosystem all-star, have the opportunity to mature into healthy adults, they can benefit eelgrass in turn by filtering phytoplankton and other excessive nutrients from the water, combating eutrophication and allowing sunlight to reach eelgrass beds. Like eelgrass, oysters reduce wave energy, decreasing erosion and sediment levels in the water. Together, oysters and eelgrass symbiotically create the living conditions for other species in the bay and form a barrier to protect against rising sea levels. Eelgrass also defends crustaceans by absorbing CO2 that dissolves into the ocean. This service is more valuable than ever as greenhouse gas emissions continue to rise. Gradually, about 30% of carbon emissions will be absorbed by the world’s oceans. Once dissolved, carbon dioxide mixes with water and forms carbonic acid. Higher carbonic acid levels cause lower pH levels and make the ocean more acidic, which slows the calcification rates of shellfish, corals, and mollusks. Since the start of the Industrial Revolution, the ocean has undergone an estimated 30 percent increase in acidity.
Eelgrass and oysters alike, are facing barriers to their posterity, primarily man-made barriers. Eelgrass is the most widely occurring marine angiosperm in the world. Yet, in 2012, covered less than 4,000 acres, or 1% of submerged land in the San Francisco Bay. Habitat alteration for recreational, industrial, commercial, and residential development has been taking a toll on this keystone species. Shoreline structures and dredging are blocking sunlight from reaching eelgrass beds. Moreover, these man-made structures and upland construction augment erosion into the bay, smothering eelgrass beds and oyster reefs in sediment. Sadly, these challenges date back to the Gold Rush. Since the 1850s, 90% of eelgrass population is thought to have been lost. Between 1800 and 1998, it is estimated that 42 percent of mudflats and 79 percent of bay marshes were eliminated, according to a 2015 report by the California Coastal Conservancy.
Although eelgrass populations are still declining, the understanding of eelgrass importance is growing. California Senate Bill 1363 was approved by Governor Jerry Brown in September of 2016, which acknowledges the role of eelgrass in promoting a healthier ocean for ecosystems and industry. This legislation funds the State Coastal Conservancy and other relevant entities, along with establishing the State Treasury of The California Ocean Protection Trust Fund. This political action provides desperately needed funding for restoration projects. There are numerous organizations, such as, NOAA, the Coastal Conservancy, EPA, Audubon California, and local universities where you can learn more about restoration efforts and ways to get involved.
“All About Eelgrass.” Richardson Bay Audubon Center, Audubon, 22 Jan. 2016, richardsonbay.audubon.org/all-about-eelgrass.
“SB-1363 Ocean Protection Council: Ocean Acidification and Hypoxia Reduction Program.” Bill Text – SB-1363 Ocean Protection Council: Ocean Acidification and Hypoxia Reduction Program., California Legislative Information, 26 Sept. 2016, leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=201520160SB1363.
Shea, Jacob. “Oysters and eelgrass, unlikely heroes in the fight against rising seas.” Richmond Confidential, Richmond Confidential, 18 Dec. 2016, richmondconfidential.org/2016/12/08/oysters-and-eelgrass-unlikely-heroes-in-the-fight-against-rising-seas/.
“The San Francisco Bay Living Shorelines: Nearshore Linkages Project .” State of California Coastal Conservancy, ESA PWA, 2012, scc.ca.gov/webmaster/ftp/pdf/restore-shoreline/sfbay-living-shorline-project-052412.pdf.
“What is Ocean Acidification?” PMEL Carbon Program, PMEL Carbon Group, www.pmel.noaa.gov/co2/story/What is Ocean Acidification%3F.