Earth’s “worst die-off” caused by “drop in ocean pH” —Report
Massive amounts of carbon dioxide released during colossal volcanic eruptions in Siberia may have turned the world’s oceans dangerously acidic 252 million years ago, causing a global environmental catastrophe that killed more than 90 percent of all species, according to a new study published Thursday.
“The largest mass extinction in Earth’s history occurred at the Permian-Triassic boundary 252 million years ago. Several ideas have been proposed for what devastated marine life, but scant direct evidence exists,” says the study.
“Now, locked in limestone that was formed in shallow seawater offshore of the supercontinent Pangaea, scientists [say they have] have found an isotopic signal to support a sharp drop in pH,” according to a report summary.
The volcanoes spewed trillions of tons of carbon dioxide into the atmosphere, some of which was dissolved in the oceans, lowering the pH and dangerously acidifying the water and weakening marine creatures’ ability to form calciferous shells.
“It appears that, although the oceans buffered the acidifying effects of carbon release from contemporary pulses of volcanism, buffering failed when volcanism increased during the formation of the Siberian Traps. The result was a widespread drop in ocean pH and the elimination of shell-forming organisms.”
The eruptions, thought to be the most powerful explosions occurred over the past 500 million years, lasted for a million years, spanning the boundary between the Permian and and Triassic Period, and resulting in the extinction event that occurred over a period of 60,000 years, said the researchers.
Permian-Triassic extinction event supposedly exceeded even the K-T extinction [officially, Cretaceous–Paleogene (K–Pg) extinction event] that occurred 66 million years ago and that allegedly erased the dinosaurs and many other animals, i.e, 75% of all species.
‘Ocean acidification and the Permo-Triassic mass extinction’
Ocean acidification triggered by Siberian Trap volcanism was a possible kill mechanism for the Permo-Triassic Boundary mass extinction, but direct evidence for an acidification event is lacking. We present a high-resolution seawater pH record across this interval, using boron isotope data combined with a quantitative modeling approach. In the latest Permian, increased ocean alkalinity primed the Earth system with a low level of atmospheric CO2 and a high ocean buffering capacity. The first phase of extinction was coincident with a slow injection of carbon into the atmosphere, and ocean pH remained stable. During the second extinction pulse, however, a rapid and large injection of carbon caused an abrupt acidification event that drove the preferential loss of heavily calcified marine biota.
M. O. Clarkson, S. A. Kasemann, R. Wood, T. M. Lenton, S. J. Daines, S. Richoz, F. Ohnemueller, A. Meixner, S. W. Poulton, E. T. Tipper
Science 10 April 2015:
vol. 348 no. 6231 pp. 229-232