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Bacteria Wreaks Havoc on West Coast Hatcheries

by Ellen Hardy
15 September 2008, at 1:00am

WASHINGTON, US - For years, the unwritten motto at shellfish hatcheries in the Pacific Northwest was "Better oysters through science." Suddenly, oyster research bogged down as a riotous bloom of bacteria went on a West Coast killing spree, wiping out billions of oyster larvae.

The outbreak first shut down an oyster brood-stock program run by Oregon State University in Newport, Ore., in 2005. "All we saw was our larvae were dying," said fisheries professor Chris Langdon, "and we couldn't put our finger on why."

Then the microscopic bacteria overran commercial hatcheries in Washington and Oregon - writes Kenneth R. Weiss in Journalnow - crippling production over the past couple of years and causing a shortage of oyster "seed" needed to replant tideland farms from Southern California to Canada.

According to Journalnow, science has identified the culprit, a strain of bacteria called Vibrio tubiashii, which is harmless to humans but fatal to baby oysters. It attacks them in their vulnerable, free-swimming larval stage before they settle to the seafloor, latch onto rocks or other oysters and grow thick shells.

The Vibrio blooms appear to be linked to warmer waters in estuaries and the oxygen-starved "dead zones" that have showed up this decade off the coast of Oregon and Washington, researchers said.

These low-oxygen waters correlate with stronger winds coming from a warming planet.

Scientists note that Vibrio tubiashii has an advantage over other microscopic sea life. This bacterium thrives in oxygen-starved dead zones, feasting on decaying plant and animal matter littering the seafloor. When brought to the surface with water welling up from the deep, it can switch survival strategies to flourish in warm, well-oxygenated waters.

Researchers were not surprised to find this type of bacteria in seawater but were stunned that it had become so dominant over other microbes. It was nearly a pure concentration of this one bacteria, one that happens to be deadly to oyster larvae.

Ellen Hardy