Unlike dinosaurs and other terrestrial animals, deep-sea creatures were able to survive the catastrophic asteroid that plummeted to Earth 65 million years ago - but how?
This question has puzzled researchers for years, as the asteroid impact was thought to have cut off the ocean's food supply by killing all free-floating algae and bacteria.
But new research from Cardiff University shows that some forms of marine algae and bacteria managed to survive, and acted as a constant, sinking, slow trickle of food for bottom dwellers.
"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," explained Heather Birch, lead author from Cardiff University's School of Earth and Ocean Sciences. "Our results show that despite a wave of massive and virtually instantaneous extinctions among the plankton, some types of photosynthesizing organisms, such as algae and bacteria, were living in the aftermath of the asteroid strike."
Drilling cores from the ocean floor in the South Atlantic revealed fossilized shells of sea surface and seafloor organisms from that time period. Researchers then analyzed the chemical composition of these samples to determine which forms of algae and bacteria prevailed after the asteroid touched down on Earth.
With this data, the team was able to infer the flux, or movement, of organic matter from the sea surface to the seafloor in the aftermath of the impact. They concluded food was constantly being delivered to the deep ocean, allowing species near the sea floor to flourish and spread into recently vacant territory.
"This provided a slow trickle of food for organisms living near the ocean floor, which enabled them to survive the mass extinction, answering one of the outstanding questions that still remained regarding this period of history," Birch added. "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."
Specifically, researchers found the ocean's food supply was fully restored about 1.7 million years after the asteroid strike. This, however, cuts previous estimates in half, proving marine food chains were able to bounce back quicker than originally thought.
This 110-kilometer-wide asteroid, which hit Mexico's Yucatán Peninsula, filled Earth's atmosphere with gases that caused mass amounts of sulphuric acid rain to fall in just a few days. This would have made the ocean far too acidic for creatures living near the surface.
Worse, debris and greenhouse gases locked in heat from the Sun, causing temperatures to rise dramatically and killing off almost half of the world's species.
Their findings were recently published in the journal Geology.
