Hog Island tracks sea changes

David Briggs
Terry Sawyer of Hog Island Oyster Company is partnering with UC Davis researchers to measure water conditions that affect the survival of oyster seed. His current inventory is only 20 percent of capacity, he said.

Hog Island Oyster Company owner Terry Sawyer has teamed up with researchers to track rising temperatures and acidity in Tomales Bay—changes that are affecting him and other farmers whose fates are linked to that of the Pacific Ocean.  

Last week, Mr. Sawyer installed a sub-surface fluorometer to measure PH, temperature and salinity. This way, researchers will be able to see how the bay’s properties change over time. “From a scientific view, we’re ready-made for a research site,” he said. “We’re out there every day, and wanted to help.”

Mr. Sawyer said researchers are approaching shellfish industry operations such as his because they are already on the water, cultivating species that are sensitive to new and often troubling shifts.

Oysters and other shellfish absorb calcium carbonate from the water and bind it together to form their shells. But that process can only take place within a specific PH range. While the bivalves have been known to adapt to slow and gradual changes, current rates of acidification are too fast for the oysters’ binding mechanism to catch up, and trouble is on the horizon.

Increases in acidity and other changes can stress oysters, and rising temperatures can increase the spread of diseases such as Vibrio tubioshii, a bivalve pathogen that can effect hatchings and wipe out entire plantings.

Mr. Sawyer’s own oysters are closely monitored for any sign of contamination, and once harvested are quickly placed in “wet storage,” where they spend a day in aerated, UV sterlized  49-degree water to be “de-stressed” and where they are further 

“This offers a more unified cooling system then packing them in ice,” Mr. Sawyer said. “It’s a day they get to kick back and have a drink.”

Last Thursday, at one of three test sites near the oyster farm’s water source, Mr. Sawyer placed a moored instrumentation package with two units, a SeaFET ocean PH sensor and a SeaCAT dissolved oxygen sensor. The devices will be removed once a month for calibration and cleaning, and their data will be downloaded and sent to Dr. Tessa Hill of Bolinas, a professor in the Bodega Marine Laboratory of the University of California, Davis.