In a new study, scientists at Bigelow Laboratory for Ocean Sciences discovered how some species of single-celled algae lived through the mass extinction of 66 million years ago. This finding could change how we understand global ocean processes.
Coccolithophores, like most algae, are photosynthetic and utilize the sun’s energy to make food. However, the aftermath of the asteroid impact was thought to have blanketed the planet with several months of darkness, the end for most of the world’s photosynthetic organisms. In combination with other fallout effects, this caused the extinction of more than 90 percent of all coccolithophore species, some of the most influential organisms in the ocean. However, others endured.
Coccolithophores are integral to processes that control the global ocean and atmosphere, including the carbon cycle. They take in dissolved carbon dioxide from the atmosphere, which gets transported to the ocean floor when they die. “That’s hugely important to the distribution of carbon dioxide on Earth,” said Senior Research Scientist William Balch. “If we didn’t have this biological carbon pump, the carbon dioxide in our atmosphere would be way higher than it is now, probably over two times as much.”
As part of the new study, the team conducted laboratory experiments that showed some coccolithophores could survive without light. This revealed that the organisms must have another way to produce the energy and carbon that they need.
“We’ve been stuck on a paradigm that algae are just photosynthetic organisms, and for a long time their capability to otherwise feed was disregarded,” said Jelena Godrijan, the paper’s first author, who conducted the research as a postdoctoral scientist at Bigelow Laboratory. “Getting the coccolithophores to grow and survive in the dark is amazing to me, especially if you think about how they managed to survive when animals like the dinosaurs didn’t.”
The study revealed how some coccolithophore species could use previously unrecognized organic compounds as carbon sources instead of carbon dioxide, which is what plants usually use. They can process dissolved organic compounds and immediately utilize them in a process called osmotrophy.
The findings may explain how these organisms survive in dark conditions, such as after the asteroid impact, or deep in the ocean beneath where sunlight can reach.
The research was published in the journal New Phytologist and co-authored by Dr. Balch and Senior Research Associate David Drapeau.
Source: Bigelow Laboratory for Ocean Sciences
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