Rapid fluctuations in oxygen levels coincided with Earth's first mass extinction

The first mass extinction may have been caused by rapid changes in marine oxygen levels.

Around 450 million years ago, life on Earth was going through a mass extinction called the LOME. Reducing habitat loss in a rapidly cooling world is one of the possible causes of the mass extinction.

The research team found that the mass extinction was preceded by a rapid decrease in marine oxygen levels and a rapid increase in oxygen. Their work is in a journal.

There were several groups of organisms that began to decline very early in the mass extinction interval, but we didn't have any good evidence of an environmental or climate signature to link that decline. Changes in oxygen can be linked to the early phase of extinction. At the same time as these organisms begin their decline into the main phase of the mass extinction event, we see a marked change in thallium isotope.

Immediately after the decrease in oxygen, there was an increase. The first die-off of mass extinction and major ice sheet growth took place over the ancient South Pole.

"Turbulence in oxygen levels in the ocean is what seems to have been problematic for organisms that were living there at that time, which may have been adapted to cope with low oxygen conditions initially or vice versa," Young said. The fact that oxygen levels in the oceans next to the continents switch back and forth over a few hundred thousand years wreaked havoc on the marine ecology.

One of the five major mass extinctions in Earth's history took place in icehouse conditions, in which widespread ice sheets are present on Earth's surface. Earth is currently experiencing icehouse conditions and loss of biodiversity, which makes this ancient mass extinction an importantAnalog for present-day conditions, along with trying to understand Earth's future as our climate continues to warm.

The previous research into environmental conditions surrounding the LOME used limestones from more oxygenated settings, but this study used shales that were deposited in deeper, oxygen -poor water, which recorded different geochemical signatures, allowing the researchers to make conclusions about global marine conditions.

The discovery of low-oxygen conditions on a global level and the coincidence with the early phases of decline in marine animals helps paint a clearer picture of what was happening with this extinction event.

Sean Newby is a PhD student at Florida State University and Jeremy Owens is an associate professor at the College of Charleston.

There is more information about the driver of the mass extinction. There is a book titled "Sci Adv.abn8345."

Journal information: Science Advances