Mass Extinction Event Had Little Impact on Marine Ecosystems

Dead staghorn coral. (Arc Centre of Excellence Coral Reef Studies)

(CN) – Despite wiping out nearly half of all life on Earth, one of the most devastating mass extinctions did not fundamentally alter marine ecosystems, a new study finds.

The cataclysmic event, which occurred during the late Triassic period, also led to the extinction of most marine species – without dramatically changing the way ocean ecosystems functioned, scientists report Friday in the journal Palaeontology.

“While the late Triassic mass extinction had a big impact on the overall number of marine species, there was still enough diversity among the remaining species that the marine ecosystem was able to function in the same way it had before,” said lead author Alex Dunhill, a paleobiologist at the University of Leeds in Britain.

Occurring about 201 million years ago, the extinction stemmed from a series of large volcanic eruptions that elevated greenhouse gas levels in the atmosphere, leading to rapid global warming. The eruptions are also linked to the break-up of the supercontinent Pangaea, as well as the opening of the Atlantic Ocean.

“We’re not saying nothing happened,” said co-author William Foster, a paleontologist at the University of Texas at Austin. “Rather, global oceans in the extinction’s aftermath were a bit like a ship manned by a skeleton crew – all stations were operational, but manned by relatively few species.”

To measure the event’s impact on the ocean, the team compared marine ecosystems across the cataclysmic event by analyzing fossils from the middle Triassic to the middle Jurassic – a span of 70 million years. The researchers classified the lifestyles of various ocean-dwelling species based on how they fed and moved and where they lived.

Their findings show that while the extinction did not shift global marine ecology, it did produce significant regional and environmental effects and had a major impact on specific ocean ecosystems.

“One of the great marine casualties of the late Triassic were stationary reef-dwelling animals, such as corals,” Dunhill said. “When we examined the fossil record we saw that while the marine ecosystem continued to function as a whole, it took over 20 million years for tropical reef ecosystems to recover from this environmental cataclysm.

“The effect of the late Triassic greenhouse gases on marine ecosystems is not so different from what you see happening to coral reefs suffering from increasing ocean temperatures today.”

Co-author Richard Twitchett added that understanding the extent of reef collapse during previous extinctions could help scientists forecast the future of modern marine ecosystems.

“Tropical ecosystems suffered widespread devastation each time that greenhouse gases rose rapidly in the past, despite differences in the rates of change and species involved,” said Twitchett, a paleontologist at the Natural History Museum in London.

“When you see similar responses occurring time and time again in the past, despite different starting conditions, it follows that similar responses will likely occur again in the future.”

 

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