Author: Carolyn Gramling / Source: Science News
A massive series of volcanic eruptions in Earth’s distant past left ocean creatures gasping for breath.
Greenhouse gases emitted by the volcanoes dramatically lowered oxygen levels in the oceans, a deadly scenario that may have been the main culprit in the Great Dying, researchers report.Earth scientist Justin Penn of the University of Washington in Seattle and colleagues mapped out just how hot the oceans got at the time of the greatest mass extinction on Earth, about 252 million years ago, at the end of the Permian Period. From those climate simulations, the team investigated where the hot water led to ocean anoxia, dangerously low concentrations of dissolved oxygen.
Then, the team combined those data with the oxygen requirements of modern ocean dwellers. The scientists determined that hypoxia — a lack of sufficient oxygen for species’ metabolic needs — could have been the primary culprit behind the die-off. The research, published in the Dec. 7 Science, also predicts that the effects of hypoxia would have been worst at polar latitudes, and available fossil data support that result.
“Anoxia has been invoked as a primary kill mechanism for the marine extinctions for 20 years,” says Lee Kump, a geochemist at Penn State who wrote a commentary on the finding in the same issue of Science. But what’s unique about this study is the inclusion of how that anoxia affects organisms living in different ecological niches within the oceans, he says.
In the Great Dying, as many as 90 percent of all marine species and 70 percent of terrestrial vertebrate species died off. Massive volcanic eruptions, discharging in pulses that began about 300,000 years before the onset of the extinction event, were almost certainly the trigger for the Great Dying (SN: 9/19/15, p. 10).
But how, exactly,…
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