Sep 29 2009

When Oceans Turn Acidic

Posted by: Jonathan Marshall

The following dispatch, regarding disturbing new findings about the acidification of the ocean due to rising CO2 levels, comes from John Lindsey, a colleague of mine at PG&E based in San Luis Obispo County:

Since the industrial age, concentrations of CO2 in the atmosphere have increased by about 100 parts per million (ppm) to about 380 ppm. Ice core samples from the Arctic show it is now higher than it has been in the last 650,000 years.

Scientists surveying the near shore waters off the California coastline have discovered higher levels of dissolved carbon dioxide in the water column.

"The absorption of atmospheric carbon dioxide (CO2) into the ocean lowers the pH of the waters" said Burke Hales, an associate professor in the College of Oceanic and Atmospheric Sciences at Oregon State University. "This so-called ocean acidification could have important consequences for marine ecosystems," he noted.

Hale recently co-authored a paper called "Evidence for Upwelling of Corrosive Acidified Water onto the Continental Shelf."

As the world's oceans absorb growing levels of carbon dioxide from the atmosphere, a greater amount of carbonic acid is formed. That has a corrosive effect on aragonite, the calcium carbonate mineral that forms the shells of many marine creatures.

This condition could have a profound effect on zooplankton, pteropods and other marine invertebrates that sustain many of our commercial fish, such as juvenile salmon. Other research indicates that abalone may also be adversely affected.

Over the last few years, the northwesterly winds have blown with greater strength and consistency, with fewer periods of relaxation. As surface waters are blown out to sea, this condition produces a greater amount of upwelling from the ocean depths and cooler near-shore seawater temperatures along the northern and central coast of California.

"The upwelling and the phytoplankton blooms have been larger along the West Coast," Hales said. "When the material produced by these blooms decomposes, it puts more CO2 into the system, decreases the levels of dissolve oxygen and increases the acidification."

"Even if we somehow got our atmospheric CO2 level to immediately quit increasing," Hales added, "we'd still have increasingly acidified ocean water to contend with over the next 50 years."

His study was funded by the National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA), and is part of a planned series of biennial observations of the carbon cycle along the West Coast of the continent.

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