Reefs took 1.5 million years to reappear after Permian-Triassic Mass Extinction

Coral reefs after Permian-Triassic Mass ExtinctionThe Permian-Triassic Mass Extinction was the largest in our planet’s history. Enormous disruptions of the carbon cycle led to climate change, ocean acidification and ocean anoxia – and with an estimated 90 percent of all species dying out Earth almost returned to a lifeless state.

Within the remaining 10 percent of biodiversity however all of Life’s Kingdoms were represented, so the seeds for recovery did exist.

That recovery took millions of years during which Earth was a desolate place, mostly home to microbes. It’s known to geology as the ‘coal gap’ – as even the forests had gone.

Coral reefs weren’t traceable in the fossil record for 5 million years, but now new research published in Nature Geoscience shows metazoan reef-building organisms were part of an ancient coastal ecosystem in what is now a Southwestern US limestone deposit ‘as soon as’ 1.5 million years after the end-Permian extinction event.

The authors think conditions for marine life remained harsh for much of the early Triassic though, but that locally the reef-building organisms managed to occupy niches whenever conditions (temporarily) improved.

Only life can restore carbon

As reefs to a large extent consist of calcium carbonates, coral creatures are thought to be vulnerable to ocean acidification. As long as atmospheric and oceanic CO2 concentrations remained high, this could have been a recurring problem for marine life for millions of years – only to be solved when life – both in the oceans and on land – for unapparent reasons managed to switch to a higher gear and total biological productivity increased, elevating oxygen levels and storing CO2 in biomass and (through that) eventually in Earth’s deep, geological carbon cycle.

Anyway, 1.5 million years is not what we had in mind when we reported on the possible quick recovery of coral reefs. So perhaps be wise about this, and let’s not complicate things by first crossing that coral extinction threshold.

© Rolf Schuttenhelm |

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