Marine Microalgae Use Light Sensors to Navigate the Ocean

Ocean-dwelling phytoplankton are known to be essential to marine ecosystems and climate regulation. Similar to terrestrial plants, they use photosynthesis to create half of the oxygen on Earth and store CO₂ from the atmosphere. Nevertheless, little is known about the mechanisms governing their distribution.

By examining how diatoms, a type of phytoplankton, perceive light, researchers from the CNRS and Sorbonne University found that these microalgae use phytochromes, which are light variation sensors encoded in their genomes. They can determine their vertical position within the water column by using these photoreceptors to detect changes in the light spectrum.

To regulate biological activity, particularly photosynthesis, this function is particularly crucial in turbulent aquatic environments that experience significant water mixing, such as high latitude, temperate, and polar regions.

After analyzing environmental genomic data from marine sampling campaigns conducted by Tara Oceans, the team discovered that only diatoms from zones outside the Tropics of Cancer and Capricorn have phytochromes.

These regions exhibit clear seasonality, including significant variations in day length, implying that phytochromes allow the diatoms that possess them to track the passage of time through the seasons.

The mechanisms by which phytoplankton detect and react to light in order to navigate their surroundings are clarified by this study, which was published in the journal Nature.

It also emphasizes how crucial integrated approaches are for comprehending the intricate dynamics of marine ecosystems and the capacity of organisms to adapt to changing environmental conditions, both in the lab and in the natural world.