Past ocean acidification considered

Yet another study looking at what happened in a previous big event of volcano driven ocean acidification 120,000,000 years ago. Yes, shell making plankton survived, morphing into smaller sizes, but at the same time the rate of acidification, and the way it changed at depth, is very different to what's happening now:

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. The length of this episode derives "most probably because several CO2 pulses [volcanic eruptions] contributed to ocean acidification," Erba says. Further, she plans to examine other high CO2 events in the geologic record to see "if the same causes—excess CO2, global warming, ocean acidification—trigger similar effects on marine calcifiers at different times."

But the 25,000-year time lag between acidification of the surface waters and deeper waters is mysterious, points out geoscientist Timothy Bralower of The Pennsylvania State University, who was not involved in this study. "In the modern ocean, a similar input of carbon would involve a lag on the order of centuries," he notes. "So something is very different." And the nannoconids begin to disappear even before the fossil record indicates lighter volcanic carbon isotopes—in other words, presumably before the actual acidification.

Here's the crux:

"The current rate of ocean acidification is about a hundred times faster than the most rapid events" in the geologic past, notes marine geologist William Howard of the Antarctic Climate and Ecosystems Cooperative Research Center in Hobart, Tasmania. Plus, the direct impacts of global warming may complicate the picture—just as modern coral suffer from increased bleaching thanks to warmer ocean temperatures as well as the reduced carbonate exoskeleton–building capacity brought on by ocean acidification. Bralower adds: "The big question is whether modern species will be able to adapt to what I expect will be much more rapid pH reduction in coming centuries."