Fossils from the past shed new light on oceans' capacity to survive future climate change

The single largest mass extinction in marine environment history did not wipe out a single key ecological group of animals according to new research published yesterday (Sunday).

Scientists studying the fossil record from the Permian period, 252 million years ago, have discovered for the first time that the ecosystem carried on functioning with a “skeleton crew” of species despite an overall dramatic loss of life due to cataclysmic climate change and rising sea levels.

The findings by researchers at Plymouth University are published in Nature Geoscience, and could provide new insight into the future state of the world’s oceans as they undergo a similar change.

Professor Richard Twitchett, of the School of Geography, Earth and Environmental Sciences, and project lead, said: “The Late Permian extinction was the single largest loss of life in the history of the Earth, and was likely to have been caused by climate change and other environmental factors linked to volcanic eruption.

“Globally it wiped out 90 per cent of marine species – but we’ve found evidence that the survivors fulfilled all of the roles needed in the ecosystem. And crucially, not one of the key ecological groups of animals that lived on or within the seafloor, and which keep ecosystems functioning, were completely eliminated.”

Professor Twitchett and PhD student William Foster compiled a detailed list of all fossil marine invertebrates known from rocks of that age, mapping where and when they lived in terms of habitat, region and latitude. They worked out how each of the species moved, what they fed upon, and what role they played in the ecosystem. The final database comprised 22,263 individual fossil occurrences and a total of 1,770 genera. The results showed that while only 20 per cent of marine life (in terms of genera) survived, benthic (seafloor) life fared better, with around 38 per cent surviving. Animals that live on and within the seafloor are particularly important in driving global nutrient cycles.

William Foster said: “The fact that none of the key benthic ecological groups were completely eliminated globally during the biggest known extinction recorded in the fossil record was unexpected and demonstrates a certain level of resilience that had not been appreciated before.

“So we might predict that the present changes will not cause complete elimination of these key functional groups, unless future extinctions turn out to be more severe than that experienced 252 million years ago. However, our results also clearly show that some ecosystems do completely collapse, especially tropical ecosystems, in particular reefs.”

The findings also go some way to explaining why there was no subsequent explosion of new animals in the Triassic period.

Professor Twitchett added: “Present day oceans are under threat from climate change, pollution and overfishing and a key scientific problem is to predict how future marine ecosystems may function in the face of such pressures. Understanding how marine ecosystems have responded to past climate change and global mass extinction events may provide some clues.

“In this case, the global oceans in the extinction aftermath were a bit like a ship manned by a skeleton crew: all stations were operational but manned by relatively few species.”