FRANCE: A new study has revealed that oxygen-depleted toxic oceans had key role in mass extinction over 200 million years ago.
Changes in the biochemical balance of the ocean were a crucial factor in the end-Triassic mass extinction, during which half of all plant, animal and marine life on Earth perished, as per the University of Southampton study.
The study reveals that a condition called “marine photic zone euxinia,” which took place in the Panathalassic Ocean- the larger of the two oceans surrounding the supercontinent of Pangaea, occurs when the sun-lit surface waters of the ocean become devoid of oxygen and are poisoned by hydrogen sulphide, a by-product of microorganisms that live without oxygen that is extremely toxic to most other lifeforms.
The international team of researchers studied fossilised organic molecules extracted from sedimentary rocks and found molecules derived from photosynthesising brown-pigmented green sulphur bacteria, microorganisms that only exist under severely anoxic conditions, proving severe oxygen depletion and hydrogen sulphide poisoning of the upper ocean at the end of Triassic, 201 million years ago.
The researchers also documented marked changes in the nitrogen composition of organic matter, indicating that disruptions in marine nutrient cycles coincided with the development of low oxygen conditions.
