Dead land species changed ocean chemistry during extinction event

Dead land species changed ocean chemistry during extinction event. An international team of scientists has demonstrated that chemical changes in the ocean during Permian-Triassic extinction event were directly caused by the collapse of terrestrial ecosystems.

In the past 550 million years, Earth has experienced five mass extinction events. The worst of these events was the Permian-Triassic extinction, also known as the Great Dying, which killed 9 out of every 10 marine species and 7 out of every 10 terrestrial species. 

Warming temperatures during the Permian period led to an explosion in diversity among terrestrial species. By the end of the Permian, however, climate conditions had become unsuitable for most life.

While the cause of the abrupt climate change is unclear, many scientists believe it was the result of catastrophic volcanic activity in a region known as the Siberian Traps.

A collection of research has shown that terrestrial ecosystems were wiped out prior to marine ecosystems. The new study confirms, for the first time, that the deterioration of land species directly impacted ocean composition. Dead land species changed ocean chemistry during extinction event

The researchers built a computer model to map chemical changes in Earth’s oceans during the period of the Permian-Triassic extinction. The model tracked both mercury and carbon cycles, which made it possible to distinguish between biological and volcanic events.

The study revealed that the collapse of terrestrial ecosystems bombarded the ocean with organic matter, nutrients, and other biologically-important elements. For most marine organisms, the chemical changes caused fatal effects. 

“In this study we show that during the Permian-Triassic transition, roughly. 252 million years ago, the widespread collapse of the terrestrial ecosystems caused sudden changes in marine chemistry,” said study co-author Dr. Jacopo Dal Corso of the University of Leeds.

“This likely played a central role in triggering the most severe known marine extinction in Earth’s history. This deep-time example shows how important the terrestrial reservoir is in regulating global biogeochemical cycles and calls for the greater conservation of these ecosystems.”

The study places new emphasis on the importance of understanding the functional interdependance of ecosystems. This is particularly relevant today, as human activities threaten to push many species past the point of survival.  

“252 million years ago the effects of mass plant death and soil oxidation appear to have seriously altered the chemistry of the oceans. This is an uncomfortable parallel with our own human-driven land use change, and we too are transferring large quantities of nutrients and other chemicals to the oceans,” said study co-author Dr. Benjamin Mills.

“As we look to re-start the world’s economies in the wake of the current pandemic, protecting our life-sustaining ecosystems should be a priority.”

The study is published in the journal Nature Communications.

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By Chrissy Sexton, Earth.com Staff Writer