Everyone knows the story of the asteroid that killed the dinosaurs. 66 million years ago the planet was plunged into darkness. The debris and soot cooled the climate by acidifying the oceans. Not only did the dinosaurs die out, but so did all the dominant species of algae. Except for one weird guy: algae became hunters.
There is no life without algae
How did you do it? An international team of scientists from Great Britain, France and the USA wanted to understand. Among them the co-author of the study: Andrew Ridwell. “If you remove the algae that form the basis of the food chain, everything else should die. We wanted to know how the world’s oceans avoided this fate. And how our modern marine ecosystem has developed again after such a disaster.
They examined well-preserved fossils of the surviving algae. They created models to simulate the evolution of algae eating habits over time. The results are in Science Advances.
Most of the fossils had calcium carbonate shields in holes and shields. Holes indicate flagella: fine, tail-shaped structures. They make tiny organisms swim. “The only reason you have to move is to catch your prey,” explains Ridgwell.
Modern relatives of ancient algae also have chloroplasts. They allow them to use sunlight to make food from carbon dioxide and water. They survive by feeding on other organisms and by photosynthesis. This is called myxotrophy. There are currently few examples of land plants with this ability. For example the Venus flytrap and the sundew.
The researchers discovered something surprising. As soon as the darkness after the asteroid was gone, these mixotrophic algae expanded from the coastal shelf areas into the open ocean. The algae that became hunters dominated for the next million years. That helped rebuild the food chain quickly.
“The results are so illustrative of the extreme adaptability of ocean plankton,” added Ridgwell. It was not until much later that algae developed and lost the ability to eat other creatures.
“Myxotrophy was the first means of survival,” explains Ridgwell. It’s the best Halloween story. When the lights go out everyone starts eating each other. ‘