In 2007, when Pacific oyster larvae began dying at the Whiskey Creek Shellfish Hatchery in Netarts Bay, Oregon, a pathogenic bacteria called Vibrio tubiashii (V. tubiashii) was originally blamed. Researchers later determined the culprit was in fact low-pH water (see “The Whiskey Creek Shellfish Acid Tests” in this issue). But that doesn’t mean V. tubiashii is off the hook.
With Oregon Sea Grant’s (OSG) backing, Chris Langdon, Oregon State University professor and head of the Newport Aquaculture Laboratory at the Hatfield Marine Science Center, is continuing to investigate V. tubiashii. He’s being joined by OSU microbiologist Dr. Claudia C. Häse, an expert in bacterial pathogens; and Dr. Ralph Elston, an affiliated professor at the University of Washington and founder of a company that performs scientific testing for the aquaculture industry.
The researchers are testing to see what effects metalloprotease, a particular protease (or enzyme) that V. tubiashii produces, might have on bivalve larvae. To do this, the researchers are subjecting the larvae of three different oyster species—including Pacific oysters—to a special mutant breed of V. tubiashii that doesn’t produce the enzyme.
Langdon says that, much like V. tubiashii’s sudden appearance in 2007, there’s been another big surprise in the knowledge that’s slowly building for this bacterial pathogen. He says the current OSG research confirmed some but not all of their original suspicions.
“[Under laboratory conditions] the initial suspected toxin [metalloprotease] does not seem to be as harmful as we originally thought,” says Langdon. But he says it’s possible that other factors are involved in determining the toxicity of V. tubiashii under hatchery conditions, including the low-pH seawater linked to the Whiskey Creek larval die-offs.
“There’s still a lot we don’t know about this bug,” he says.