Humboldt Bay’s clean yet productive waters are one of the main reasons it is home to both extensive eelgrass beds and an expanding shellfish aquaculture industry that generates more than $10 million in sales per year.
Yet the aquaculture industry must now contend with a new threat that is altering the chemistry of seawater: ocean acidification. The impact of intensifying ocean acidification on aquaculture in Humboldt Bay, and the extent to which eelgrass may reduce these impacts, is the focus of a new project by California Sea Grant Extension Specialist Dr. Joe Tyburczy and collaborators at Humboldt State University, with funding awarded by the Ocean Protection Council.
The team, which includes industry partner Terry Sawyer of Hog Island Oyster Company, will install a state-of-the-art monitoring instrument called a Burkolator to track Humboldt Bay’s carbonate chemistry at the company’s new oyster hatchery. The researchers will place additional sensors in coastal waters outside the bay and establish the first bay-wide monitoring program for eelgrass.
“Our goal is to provide the aquaculture industry and environmental permitting agencies with data and information that will help them develop win-win scenarios – ones that allow the aquaculture industry to expand, while at the same time minimizing impacts on eelgrass and the services it provides,” said Tyburczy.
Humboldt Bay is one of the few places that can export seed and larvae of oysters and clams anywhere on the West Coast, thanks to a monitoring program called the High Health Plan that ensures bivalves grown there are free of damaging parasites and diseases. Larvae, which are produced in hatcheries, are the earliest life-history stage of oysters and clams, and are especially susceptible to ocean acidification.
“Humboldt Bay is an excellent place to be doing this work because aquaculture is already a major, important industry here. It’s got really good growing conditions for oysters, and based on measurements taken in the region, we believe the acidity of seawater in the Bay is somewhat buffered – likely by eelgrass,” said Tyburczy, noting that shellfish hatcheries in other locations must often resort to artificially buffering acidic water with chemical additives to keep their larvae alive. “We hope to get a handle on how buffered the Bay is, how much of that buffering is done by eelgrass, and how oyster growers can get the most benefit from this natural buffering and protect their product.”
Tyburczy said protecting Humboldt Bay’s eelgrass is equally important, as it forms the basis of the ecosystem and makes up nearly half of the remaining eelgrass beds in California. Other communities have not been so lucky. In Morro Bay, eelgrass cover declined from 344 acres in 2007 to just 10 acres by 2013, a 97 percent loss in just 6 years. The project’s monitoring program will help catch any such declines in Humboldt Bay early on so that they can be addressed.
“Eelgrass is to the bay what trees are to a forest,” said Tyburczy. “It provides structure and nursery habitat for many species including fish and crabs, and makes the Bay an important food source and stopover for black brant geese and other migratory birds along the Pacific Flyway.”
“We want to quantify the ecosystem service of water buffering that eelgrass provides, by removing excess carbon dioxide from the seawater during photosynthesis. This effect will benefit not only cultivated species, but wild organisms as well,” Tyburczy said. “Another key question we will examine is whether farming adult oysters within eelgrass beds impairs this buffering function.”
The project will begin this spring with the installation of carbonate sensors, which will be led by Dr. Jeff Abell of HSU and Dr. Burke Hales of Oregon State University, inventor of the Burkolator. Data produced by these new instruments will be made freely available and streamed in real-time at the website of the Central and Northern California Ocean Observing System (CeNCOOS).
Tyburczy will lead measurement of how the carbonate chemistry of seawater changes as it flows over eelgrass beds, using the same methods employed by Dr. Tessa Hill of UC Davis in Tomales Bay and Bodega Bay with project support from California Sea Grant. Similar studies are slated to begin in Elkhorn Slough, Newport Bay, and San Diego Bay – allowing comparisons among these locations.