Ancient Ocean 'Dead Zone' Delayed Recovery After Mass Extinction | K-T Extinction & Marine Life | Nutrient-Enriched Oceans | LiveScience
A flood of nutrients may have created an oxygen-starved ocean
about 250 million years ago, preventing life from bouncing back for a few million years after a mass extinction wiped out 90 percent of marine species, a new study indicates.
The enriched, yet oxygen-starved ocean would have been similar to today's dead zones that appear in the modern ocean often as a result of agricultural runoff, as in the Gulf of Mexico
The Permian-Triassic extinction, which hit about 250 million years ago, is believed to have been the result of widespread volcanic eruptions in what is now Siberia, which poured carbon dioxide into the atmosphere. Although the dates are inexact so far, it seems that life took an unusually long time to recover — possibly as much as 5 million years. [Oceans in Peril: Primed for Mass Extinction?]
Too much of a good thing
Chemical evidence from limestone deposited on the ocean floor during this time indicates that too much of a particular kind of life — tiny photosynthetic organisms, like certain bacteria and possibly algae — may have kept other marine species from [...]
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The study appeared online in the journal Earth and Planetary Science Letters.
You can follow LiveScience writer Wynne Parry on Twitter @Wynne_Parry.
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