Volcanoes 'destroyed ancient ocean life'
It is thought that sulphur produced by volcanoes erupting led to oxygen disappearing from large areas of the oceans.
This caused up to 27 per cent of ocean life being destroyed, according to a report published in the journal Nature Geoscience.
It is feared that a similar effect is being witnessed today as rising sea temperatures and fertilisers washing into the oceans cause oxygen levels to fall.
Scientists believe that during the Cretaceous period, a spate of volcanic activity caused plant life to bloom on the surface of the oceans.
As that plankton sank, it fed a secondary boom among the bacteria below, consuming much of the oxygen in deeper waters.
With dwindling oxygen levels, marine animals were unable to survive, wiping out large chunks of their population.
Previously, it has been held that carbon dioxide in the atmosphere was the cause of the ocean being fertilised, as rising levels brought climatic changes, washing more nutrients into the sea.
However, the new study poses an alternative theory, that a build-up of sulphur in the half million years before the so-called Ocean Anoxic Event that occurred 94.5 million years ago was to blame.
Professor Matthew Hurtgen, one of the study’s authors, told The Times: “Sulphates help the ocean hang on to its phosphorous.
“Along with nitrogen and iron, phosphorous is a key limiting nutrient in the ocean. Without it phytoplankton cannot grow. But when massive volcanism delivered more, it changed the amount of phosphorous available, and drove these anoxic events.”
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