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Ancient Ocean Acidification Intimates Long Recovery from Climate Change http://apocadocs.com/s.pl?1280158722
Of course the present era is hardly the first time the planet has seen higher levels of CO2. In fact, roughly 121 million years ago--during an age known as the early Aptian--global CO2 levels were likely higher than 800 ppm (and possibly as high as 2,000 ppm) thanks to cataclysmic volcanic eruptions. Now new research published in Science July 23 shows how ancestors of today's nannoplankton fared in those acidic oceans of long ago.
It was a time of "severe global warming," paleobiologist Elisabetta Erba of the University of Milan and her colleagues wrote, after studying the carbon isotopes embedded in deep seabed cores drilled in the Pacific Ocean and locations in the ancient Tethys Ocean, which existed during the Mesozoic era. The records reveal that acidification proved a big problem for nannoplankton. "During the Aptian episode, marine calcifiers experienced a major crisis due to increasing CO2-induced acidification," Erba says.
But that crisis was not a major extinction event. The nannoplankton responded by doing less shell-forming--the heaviest shell-formers, known as nannoconids, largely disappeared from the fossil record (although they did not go extinct, the same species reappear after acidification dwindles)--and by diversifying into new, smaller species. In some cases species even increased in abundance but shrank in size--by as much as 60 percent. "Malformation is also ascertained for some [widespread] species," Erba notes. It took at least 25,000 years for the new acidity levels reached in the surface waters to transfer to deeper waters, according to the research -- and the ocean took 75,000 years to reach its peak acidity for that episode, as well as at least 160,000 years to recover.... Regardless, the shells of at least one modern foraminifera in the Southern Ocean are already smaller than those of their ancestors from a mere century ago. And the modern buildup of atmospheric CO2 is happening far faster than these ancient episodes. "The current rate of ocean acidification is about a hundred times faster than the most rapid events" in the geologic past..."
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