The original version of This story appeared in Quanta Magazine.
Most of the life cars run on sunlight. Photons filter through the atmosphere and are eagerly recorded by league -driven organisms such as plants and algae. Through photosynthesis, the particles of light power are a cellular reaction that produces chemical energy (in the form of sugars), which is then transferred to the food web in a complex dance of herbivores, predators, scavengers, decomposers and more.
On a bright, sunny day there is a wealth of photons to go around. But what happens at low light? Biologists have long been curious about how few light photosynthesis can continue – or how many photons should turn up, and how quickly, for the photosynthetic machinery of a cell to process carbon dioxide in oxygen and energy. Calculations have suggested that a theoretical minimum of about 0.01 micromole photons per square meter per second, or less than hundreds of thousands of the light of a sunny day.
This calculation was theoretical, given the problems of studying photosynthesis under low light. No one could confirm it in the field, although there are many places on earth that barely reach the light. Every winter in the high Arctic, for example the sun, hidden by the tilt of the earth, disappears for months. Meters snow blanket the sea -ice and block incoming light, leaving the icy ocean under as dark as the inside of a grave. Biologists adopted, photosynthesis of microalgae living in the water and ice power for the season and waited until the warmth and light returned.
“People thought of the pool night as these desert conditions where there is very little life, and things sleep and hibernate and wait for the next spring,” says Clara Hoppe, a biogeochemist at the Alfred Wegener Institute in Germany. “But people really never really looked at it.”
In winter 2020, Hoppe lived on a ship in an ice flea for months, through the polar night, to study the boundaries of photosynthesis in the dark. Her team’s recent study in Nature Communications reported that microalgs grow and reproduce at light levels on or near the theoretical minimum – much lower than previously observed in nature.
The study shows that life in some of the coldest, darkest places on earth blooms with the crunch of quantum of light. “At least, under some circumstances, a phytoplankton can do very useful things on very low light,” says Douglas Campbell, a specialist in aquatic photosynthesis at Mount Allison University in Canada, who was not involved in the study. “This is important work.”
The power of the dark side
Scientists have traditionally understood the Arctic a large part of the year as a place of stasis. In winter, organisms that can flee from the icy waters; Those who stay from mountains reserves, or sink into a quiet sleep. Then, when the sun returns, the place comes alive again. During the spring flowering, an increase in photosynthesizing algae and other microbes kicks the Arctic ecosystem, which attracts an annual revelation with small crustaceans, fish, seals, birds, polar bears, whales and more.
It seemed to hoppers that any phytoplankton had an earlier start than the competition could have a more successful summer. It made her wonder when the organisms could respond exactly to the light coming back.