Algae and bacteria may have helped
The asteroid that struck just off the coast of the Yucatan peninsula 65 million years ago sealed the fate of most dinosaurs, giant marine reptiles, invertebrates, plants, and even microbes. But mysteriously, deep-sea-dwelling creatures managed to survive the catastrophic impact.
Scientists have recently found clues that shed light on the remarkable persistence of life at the bottom of the ocean during this time. A team led by researchers at Cardiff University’s School of Earth and Ocean Sciences analyzed the chemical compositions of drilling cores from the ocean floor in the southeast Atlantic. These cores contained fossilized shells of organisms that inhabited the ocean around the time the asteroid hit.
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"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," said Dr. Heather Birch, who led the study published this month in the journal Geology.
"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 said.
Fallout from the asteroid impact would have spurred a devastating “impact winter,” plunging the earth into darkness and blocking photosynthesis. Simultaneously, the impact likely created a gas cloud that would have triggered acid rain, making the surface of the ocean highly acidic and deadly to upper-ocean creatures.
Organisms inhabiting greater ocean depths were able to sustain themselves and certainly fared better than their upper-ocean counterparts. However, it would still be about 1.7 million years before their food supply would be completely restored, allowing opportunities for new species to evolve and fill niches that had been vacated by those that went extinct.
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