The ocean on acid

If you’ve ever had an aquarium, you know pH is everything. One slight fluctuation can send fish belly up.

Scientists say a precise pH level is also critical for the health of the world’s oceans — particularly any creature with a shell.

Yet human activities are sending unprecedented levels of carbon dioxide into the water, and making it more acidic, scientists reported at the American Association for the Advancement of Science meeting recently in San Diego.

Marine scientists are not yet sure what effect ocean acidification is having on local marine life such as shellfish found in San Diego’s waters. They do believe a more acidic pH is harming coral-rich areas like Australia’s Great Barrier Reef.

Crustaceans such as oysters and clams will also be vulnerable as the waters become more corrosive — researchers say they’ve grown 30 percent more acidic since the start of the industrial revolution.

The underlying problem causing the global rise in acidity is carbon dioxide, which gets absorbed in seawater and makes it more corrosive. According to Stanford University estimates, industry pumps 1,000 tons of carbon dioxide into the atmosphere each second.

A third of the CO2 in the atmosphere dissolves into the oceans. The West Coast is especially susceptible because of upwelling currents that carry high volumes of carbon dioxide from deeper waters, said Vicky Fabry, a Cal State San Marcos biologist who researches ocean acidification.

Oceanic researchers have already found waters corrosive enough to harm shellfish reaching a Northern California shoreline during a field study several years ago.

Fabry is part of a research team launching a three-year field study off that same stretch of coastline near Humboldt County this month. They’ll be monitoring how several key species, like red abalone, respond to the upwelling waters.

She will also collaborate with researchers at the Scripps Institution of Oceanography on a lab experiment exposing commercially viable species like sea urchins, oysters and abalone to fluctuating levels of carbon dioxide.

Anything with a shell, Fabry suspects, could be in trouble if waters continue to acidify off the California coast. Shells are made of calcium carbonate, which dissolves in the presence of acid.

“If you go to a rocky inter-tidal beach at low tide and you look at all the different organisms, most of them are calcified,” she said. “Think about that. Think about what if none of them could live in a high CO2 ocean. What would be left?”

Rebecca Tolin, Voice of San Diego, 1 March 2010. Full article.

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