Scientists: Ocean acidification threatens Dungeness crab
A crab-fishing ban that California officials put in place in November wasn't lifted until late last week when the last area closed because of an El Nino-induced toxic algae bloom was allowed to re-open to commercial crabbing.
Citing economic losses of some $49 million during the crabbing ban, California Gov. Jerry Brown asked the U.S. Commerce Department to declare the season a disaster. But more trouble is brewing for the crab-fishing industry.
In a report released this month in the journal Marine Biology, National Oceanic and Atmospheric Administration researchers said Dungeness crabs are threatened because of ocean acidification caused from climate change.
"Is this an aberration, or is this what the future is going to look like?" said Glen Spain, northwest regional director for the Pacific Coast Federation of Fishermen's Associations. "The norm has changed."
NOAA researchers believe the ocean will become more acidic because of high levels of carbon dioxide in the atmosphere.
Researchers conducted experiments in Washington's Puget Sound with different pH levels to record effects on the crabs. As the pH level goes down, the acidity level rises, with 7.0 neutral on the pH scale.
The survival rate of Dungeness crab larvae decreases as ocean pH levels drop, according to NOAA researchers. At roughly pH 8.1, the current level in the ocean, 58% of crab larvae survived 45 days.
At pH 7.5, which sometimes occurs in the Puget Sound, survival dropped to 14%.
"I have great faith in the resiliency of nature, but I am concerned," said Jason Miller, lead author of the research. "Crab larvae in our research were three times more likely to die when exposed to a pH that can already be found in Puget Sound, our own backyard today.
Dungeness crab is the largest fishery in Washington and Oregon and the second largest in California, worth about $67 million.
Three hundred years ago, the ocean's pH level was 8.2, but as the oceans have absorbed more carbon dioxide from the atmosphere, their acidity level has risen. Scientists are predicting ocean surface pH levels to drop to around 7.8 by 2050.
Dungeness crab, a West Coast delicacy, isn't the only species threatened by changes in the oceans' chemical makeup. The higher acidity level makes it more difficult for some shellfish — such as oysters and clams — to make their shells, according to NOAA.
Spain said he was particularly concerned about effects of acidification on zooplankton, one of the tiny animals that form the basis of the ocean's food chain.
"It's one of those things that wake me up at night sweating," Spain said. "It's a big problem."
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