The phytoplankton thriving in our oceans are crucial for marine life and play an essential role in regulating the climate. Similar to land plants, they absorb carbon dioxide from the atmosphere and generate half of the Earth’s oxygen through photosynthesis. Nevertheless, how their distribution is governed is still not fully understood.
The phytoplankton that populate oceans are known to play a key role in marine ecosystems and climate regulation. Like terrestrial plants, they store atmospheric CO2, and produce half of our planet’s oxygen via photosynthesis. However, the mechanisms that control their distribution remain poorly understood.
Researchers from the CNRS and Sorbonne University1,2 investigated how diatoms, a category of phytoplankton, sense light. They discovered that these microalgae possess light-sensitive proteins called phytochromes, encoded in their genetic material. These photoreceptors allow diatoms to perceive shifts in the light spectrum within the water, helping them determine their position in the water column. This ability is particularly vital in dynamic aquatic environments where water is frequently mixed, such as in high-latitude, temperate, and polar areas. This adaptation is crucial for optimizing their biological activities, especially photosynthesis. By examining genomic data collected from marine samples by TaraOceans, the research team found that only diatoms located beyond the Tropics of Cancer and Capricorn carry phytochromes. These regions experience significant seasonal changes, including variations in the length of daylight, which suggests that phytochromes help these diatoms track seasonal shifts.
This research, published in Nature on December 18, 2024, provides new insights into how phytoplankton recognize and respond to light, navigating their surroundings effectively. It underscores the significance of combined laboratory and field approaches to understanding the intricate dynamics of marine ecosystems and how organisms adapt to environmental changes.
1- The researchers are part of the Chloroplast Biology and Light-sensing in Microalgae Laboratory (CNRS/Sorbonne University) at the Institute of Physico-Chemical Biology (CNRS), collaborating with the Institute of Biology at École normale supérieure (CNRS/INSERM/ENS-PSL).
2- This is a joint project with the TaraOcean Foundation, a key player in collecting genomic environmental data, and the Zoological Station Anton Dohrn in Naples, which focuses on biological oceanography, supported by the Bettencourt Schueller Foundation and the Dynamo Labex.
