How deep sea creatures survived asteroid hit that killed dinosaurs

When a 110-km wide asteroid struck the Earth some 65 million years ago and wiped out dinosaurs, a "trickle of food" helped deep sea creatures survive the catastrophic asteroid strike, researchers have revealed.

Like dinosaurs, 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.

Now, a team led by Cardiff University provides strong evidence suggesting that some forms of algae and bacteria were actually living in the aftermath of the asteroid disaster.

These acted as a constant, sinking and slow trickle of food for creatures living near the seafloor.

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.

"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," explained Heather Birch, PhD from Cardiff University's school of earth and ocean sciences.

The team were 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.

Furthermore, the team were able to calculate that the food supply in the ocean was fully restored around 1.7 million years after the asteroid strike, showing that marine food chains bounced back quicker than originally thought.

"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 added in a paper published in the journal Geology.

Scientists believe that the mass extinction of life on Earth around 65 million years ago was caused by an asteroid that hit Mexico's Yucatán Peninsula.