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Earth biochemical balance 'change'

Published 01/04/2015

Scientists found a condition called marine photic zone euxinia took place in one of Earth's prehistoric oceans
Scientists found a condition called marine photic zone euxinia took place in one of Earth's prehistoric oceans

The Earth could be suffering from shifts in its biochemical balance similar to those believed to have wiped out half of all plant, animal and marine life 200 million years ago, according to research.

The study by the University of Southampton reveals that a condition called marine photic zone euxinia took place in one of the prehistoric oceans.

This occurs when the sun-lit surface waters of the ocean become devoid of oxygen and are poisoned by hydrogen sulphide, a by-product of micro-organisms that live without oxygen which is extremely toxic to most other lifeforms.

The study authors fear that the planet today could suffer similar consequences caused by the amount of carbon dioxide being created through the burning of fossil fuels.

The international team of researchers studied fossilised organic molecules extracted from sedimentary rocks that originally accumulated on the bottom of the north-eastern Panthalassic Ocean, which surrounded the continent of Pangaea. The rocks are now exposed on the Queen Charlotte Islands, off the coast of British Columbia, Canada.

The experts found signs of bacteria which had suffered severe oxygen depletion and hydrogen sulphide poisoning which would have been caused by massive volcanic rifts in the Earth's tectonic plates.

Professor Jessica Whiteside, who co-authored the study published in Geology, said: "As tectonic plates shifted to break up Pangaea, huge volcanic rifts would have spewed carbon dioxide into the atmosphere, leading to rising temperatures from the greenhouse effect.

"The rapid rises in CO2 would have triggered changes in ocean circulation, acidification and deoxygenation.

"These changes have the potential to disrupt nutrient cycles and alter food chains essential for the survival of marine ecosystems. Our data now provides direct evidence that anoxic, and ultimately euxinic, conditions severely affected food chains.

"The same CO2 rise that led to the oxygen-depleted oceans also led to a mass extinction on land, and ultimately to the ecological takeover by dinosaurs, although the mechanisms are still under study."

She explained that although the Earth was very different during the Triassic period, the rate of carbon dioxide release from volcanic rifts are similar to those we are experiencing now through the burning of fossil fuels.

Prof Whiteside said: "The release of CO2 was probably at least as rapid as that caused by the burning of fossil fuels today, although the initial concentrations were much higher in the Triassic. The consequences of rapidly rising CO2 in ancient times inform us of the possible consequences of our own carbon dioxide crisis."

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