For hundreds of thousands of years, the levels of carbon dioxide in the ocean and the atmosphere were in balance, but the burning of fossil fuels and deforestation has put more CO2 into the atmosphere over the last 150 years. The oceans have absorbed one-third -- about 130 billion tons -- of those human emissions and have become 30 percent more acidic as this extra CO2 combines with carbonate ions in seawater, forming carbonic acid.
Each day, the oceans absorb 30 million tons of CO2, gradually and inevitably increasing their acidity and leaving less calcium carbonate in the water for corals and shell-form species like phytoplankton to grow or maintain their skeletons.
On the west coast of North America, there is normal upwelling of deep ocean water onto the continental shelf in the spring and summer. Feely and colleagues took water samples from Canada to Mexico last summer and much to their surprise they found big pools or shoals of corrosive water. These deep waters have been absorbing CO2 for thousands of years and are normally more acidic, but the levels found were far higher and much closer to the shore than anyone had expected.
This is the first evidence that a large section of the North American west coast is being impacted by climate change-driven ocean acidification, Feely and colleagues write in their paper published Thursday in Science. "Other continental shelf regions may also be impacted," they write.
In fact, Feely told IPS that there is evidence that the same process is happening along the west coast of South America.
So what does this mean? "There are likely huge impacts, but this is new and no one has looked to see yet," Feely said.
Continental shelves are among the most productive regions of the oceans and the easiest to fish. The very few studies looking at the impacts of ocean acidification have found that many species cannot survive these new conditions. Brittlestars (a close relative of starfish) die in eight days, and some juvenile clams can't form shells when the CO2 levels are doubled, Feely said. Some of the surface waters last summer were triple the normal CO2 levels.
And there is no information at all on how the marine ecosystem responds when these pools of corrosive water move in for a few days or weeks. "Do species like free-swimming pteropods (a type of snail) know when their thin shells are dissolving so they can get out of the way?" he asked.
That turns out to be an important question for species like salmon, since pteropods can make up 60 percent of their diet.
Temperature rise and acidification are putting one of the planet's key ecosystems at great risk, Feely warned: "This is a very real biological threshold beyond which species will simply cease to exist."
Coral reefs support about 25 to 33 percent of the oceans' living creatures. Some one billion people depend directly and indirectly on reefs for their livelihoods. Sea birds and many species of fish would be affected by the loss of reefs, said Ove Hoegh-Guldberg, a marine scientist at the Center for Marine Studies at the University of Queensland, Australia.
When CO2 in the atmosphere reaches a concentration of 450 to 500 parts per million (ppm), the oceans will mostly be too acidic for corals to grow. Warmer ocean temperatures of just one or two degrees above normal can not only can cause coral bleaching but also make corals vulnerable to even lower levels of acidification, said Hoegh-Guldberg, who attended the Gijon meet.
CO2 is at 384 ppm currently and rising very fast as nearly every country's emissions continue to grow. Worse, new research also presented in Gijon suggests the oceans themselves are no longer absorbing as much CO2 as they once did. Stabilising the atmospheric concentration of CO2 at less than 450 ppm now looks to be impossible.
"We are witnessing the end of corals as a major feature in the oceans," Hoegh-Guldberg told IPS.
The faint hope for corals is for global society to realize climate change is "a code red emergency" and cut carbon emissions to zero and start reducing the concentrations in the atmosphere right away, he said. "Otherwise in 30 years or so corals will be so thin and brittle if you breathe on them they will fall over."
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Albion Monitor May
22, 2008 (http://www.albionmonitor.com)
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