Sunday, August 1, 2010

Oysters without even a half-shell

Interesting article in the Seattle Times examining the fact that billions of Pacific oyster larvae have died and oysters in the wild on Washington's coast haven't reproduced in six seasons. Scientists suspect ocean-chemistry changes linked to fossil-fuel emissions, the oceans are becoming more acidic (which the article calls 'corrosive'), are killing the juvenile shellfish. The article goes on to list a variety of changes being observed and suggests an 'upheaval,' perhaps akin to a regime shift, may be underway.

Signs environmental upheaval may be under way:

Sea snails: Tiny sea snails called pteropods, which make up 60 percent of the diet for Alaska's juvenile pink salmon, essentially dissolve in corrosive waters. Some microscopic plankton also are important fish food, and some are highly susceptible to corrosive water.

Clownfish: Scientists in Australia found that larval clownfish and damselfish exposed to corrosive waters tended to follow the scent of predators and were five to nine times more likely to die.

Killer whales: The ocean will absorb less background noise — in effect, become noisier — when pH levels drop by even small amounts. Research hasn't been done to detail what impact, if any, that might have on marine mammals such as orcas that rely on biosonar.

Giant squid: Scientists say the giant squid, also known as the Humboldt squid, typically found at depths of 660 to 2,300 feet, grow lethargic when subjected to acidified waters.

Sea urchins: Purple sea-urchin larvae exposed to acidifying waters were smaller, "stumpier" in shape and had less skeletal mass.

Oysters: Wild Pacific oysters have not reproduced in Willapa Bay for six years. Scientists suspect acidifying water, rising from the deep in coastal "upwelling" events, is helping wipe out juvenile oysters before they can grow.

Seagrass: All five species of seagrass that have been studied were found to thrive in increasingly corrosive waters.

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