Incredibly, an adult oyster can filter up to 50 gallons of water a day, allowing sunlight to penetrate so that foundations of the food chain can thrive; once water clarity increases, bottom vegetation, such as eelgrass, flourish.
The general public is unaware that beds of bivalve shellfish provide ecosystem services by naturally filtering nutrients from the water. Bivalve shellfish are filter feeders that remove suspended solids from surrounding waters, thereby increasing water clarity, enabling seagrass growth and reducing the likelihood of harmful algae blooms. Bivalve shellfish were once the global ecosystem engineers and enablers of prosperous habitats for other species.
According to the Chesapeake Bay Foundation, enormous oyster beds “could once filter a volume of water equal to that of the entire Chesapeake Bay (about 19 trillion gallons) in a week. Today, it would take the remaining Bay oysters more than a year.
“Native Olympia oysters were once ecologically and economically dominant along coastal Southern California. “Olys” were considered commercially important as a delectable food source until a combination of over-harvesting, dredging, pollution, and wetlands destruction in the 1930s depleted natural populations.
Recent Southern California oyster restoration initiatives in Newport and Alamitos Bays were designed for “habitat not harvest”. Nor do these projects measure the impact of increased oyster populations for mitigating eutrophication, which is the over-enrichment of an ecosystem with chemical nutrients, typically nitrogen, phosphorus, or both. Quantifying the ecosystem services of oysters could create economic incentives for expanding and accelerating restoration programs. Studies conducted on the East Coast reveal that the cost of removing nitrogen with wastewater plans is about $28 per pound. For every 2,000 oysters harvested, about a pound of nitrogen is removed which is dwarfed by the nitrogen removal by bivalve bacterial denitrification.
Could native Olympia oysters once again become a nutritional food source while also improving the water quality in Southern California? Successful programs in Oregon, Washington, and the Chesapeake Bay have set positive precedents.
Oyster gardening, pioneered on the Chesapeake Bay, is a community-based program for growing baby oysters in bags under docks, piers, and other structures until the “spat,” reaches a size making them safe from predators. The spat is then released onto nearby oyster beds where their density promotes propagation. Citizen scientists get hands-on harvesting experience while learning the economic and ecological benefits of the marine habitat.
KZO Education is promoting oyster gardening legislation for the State of California and is developing plans for a local hatchery to produce the requisite native shellfish seed. Oyster gardening may be a low cost option for cleansing estuaries and coastal embayments but could they be ever be eaten? Since the oysters will be suspended in cages from the bottom there is no danger from heavy metals so that leaves bacteria and toxins, which can be detected during episodic contamination seasons and not harvested.
Quoting Jonathan Swift: "Twas a brave man indeed that 'et the first oyster". If there are no future blogs, I was the brave man that et that oyster from Alamitos Bay.