Ocean acidification could cause “crash” in marine food webs

David Gutierrez
If industrial carbon dioxide emissions are not drastically scaled back, they will soon cause a crash in the marine food web, coral specialist John Guinotte and colleagues have warned.

The ocean currently absorbs 22 million tons of carbon dioxide per day — roughly one-third of all carbon dioxide emitted from the planet’s surface — thereby muting the scale of global warming. Once dissolved in ocean water, this carbon dioxide turns into acid. Scientists say that the ocean is already 30 percent more acidic than it was before the industrial revolution.

These acids pull carbonate ions out of sea water, removing a critical component of the coral and shellfish skeletons.

“Ocean water becomes increasingly corrosive to calcium carbonate,” Guinotte said. “A reduction in carbonate ions not only impedes corals’ ability to build their skeletons, but once the calcium carbonate drops below critical levels, the ocean erodes the framework they have built up previously — the reefs upon which corals live.”

Increased acidification may cause some reefs to dissolve outright, while others may be so weakened that they can no longer resist the elements.

Because reefs are a major aquatic habitat life, their loss could devastate the entire marine food web. Equally alarming, the fossil record shows that reefs can take millions of years to recover from such damage.

“Given that we need to think in human time scales, it means we’re playing for keeps here,” Guinotte said.

“Moreover, ocean acidification is likely to become a positive feedback to global warming by slowing down the rate at which the seas can absorb society’s future carbon dioxide emissions,” writes Mark Lynas in his book“Six Degrees: Our Future on a Hotter Planet.

“From the standpoint of the oceans, there is no escaping the fact that we are going to need major reductions in our CO2 emissions — something like 80 to 90 percent,” he said. “When we see governments arguing about reductions of 10 to 15 percent, I think all of us in the marine science community need to say that CO2 reductions of this scale are simply not going to be sufficient. We have to get off fossil fuels.”

Sources for this story include: http://www.grist.org/article/2010-0….


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