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How deep-sea creatures survived dinosaur-killing asteroid

Friday, Apr 15, 2016,17:25 IST By Metrovaartha A A A

London | Scientists have solved the mystery behind how deep sea creatures managed to survive the catastrophic asteroid strike that wiped out the dinosaurs 65 million years ago. Like the dinosaurs themselves, giant marine reptiles, invertebrates and microscopic organisms became extinct after the asteroid impact in an immense upheaval of the world’s oceans, yet deep sea creatures managed to survive.

This has puzzled researchers as it is widely believed that the asteroid impact cut off the food supply in the oceans by destroying free-floating algae and bacteria. However, a team led by researchers from Cardiff University in the UK provides strong evidence suggesting that some forms of algae and bacteria were actually living in the aftermath of the asteroid disaster, and that they acted as a constant, sinking, slow trickle of food for creatures living near the seafloor.

The team was able to draw these conclusions by analysing new data from the chemical composition of the fossilised shells of sea surface and seafloor organisms from that period, taken from drilling cores from the ocean floor in the South Atlantic.

This gave the researchers an idea of the flux, or movement, of organic matter from the sea surface to the seafloor in the aftermath of the asteroid strike, and led them to conclude that a slow trickle of food was constantly being delivered to the deep ocean.

Researchers were able to calculate that the food supply in the ocean was fully restored around 1.7m years after the asteroid strike, which is almost half the original estimates, showing that marine food chains bounced back quicker than originally thought.

The global catastrophe that caused the extinction of the dinosaurs also devastated ocean ecosystems. Giant marine reptiles met their end as did various types of invertebrates such as the iconic ammonites, said Heather Birch, a Cardiff University PhD, who led the study.

Our results show that despite a wave of massive and virtually instantaneous extinctions among the plankton, some types of photosynthesising organisms, such as algae and bacteria, were living in the aftermath of the asteroid strike. This provided a slow trickle of food for organisms living near ocean floor which enabled them to survive the mass extinction, answering one of the outstanding questions that still remained regarding this period of history, said Birch.

Even so, it took almost two million years before the deep sea food supply was fully restored as new species evolved to occupy ecological niches vacated by extinct forms Birch said. Many scientists currently believe that the mass extinction of life on Earth around 65m years ago was caused by a 110km-wide asteroid that hit Mexico’s Yucatan Peninsula. It is believed the debris from impact starved Earth of the Sun’s energy and, once settled, led to greenhouse gases causing temperatures to rise drastically.

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