Researchers from Irig/LPCV have shown that algae develop around the edges of ice crystals in the water flowing through the snow. Biologists have analyzed the cellular architecture of the algae using 3D electron microscopy. They have thus revealed the adaptations that allow it to multiply in the snow. For instance, they observed that the cellular membrane of Sanguina is covered with tiny wrinkles that increase its contact surface with the exterior. This allows the algae to better extract the ions necessary for its growth from an environment extremely poor in nutrients.
Alpine glaciers sometimes turn a thin layer of red or orange in spring. This phenomenon, called "glacier blood," is due to a microscopic algae: Sanguina nivaloides. Researchers from Irig/LPCV study this organism at the heart of a yet unknown snow ecosystem.
© Jean-Gabriel Valay/Jardin du Lautaret/UGA/CNRS. The inside of the cell also held surprises. The algae is equipped with a single chloroplast. Within it, the thylakoids, these lamellar structures where photosynthesis occurs, are not oriented in a single direction as in most plants. In
Sanguina nivaloides, they fan out to receive light from all directions. This is an adaptation unique to life in the snow, an environment where light diffuses and reflects as in a hall of mirrors. The mitochondria, the cell's energy cores, are positioned directly on the periphery of the chloroplast to utilize the starch it synthesizes (see image under the title).
The research team was also interested in the algae's red pigments. They are not, as previously thought, used to protect the cell nucleus from UV radiation. Composed of carotenoids, they allow the algae to protect itself against the detrimental effects of oxidizing free radicals, in an environment enveloped in very intense light.
After the snow melts, the algae finds itself in the soil and undergoes a true metamorphosis to adapt to a radically different environment. Scientists now want to understand this process, which has never before been studied. Time is of the essence because the entire ecosystem dependent on
Sanguina nivaloides is threatened by climate change and the reduction of snow cover in mountains.
References:
Ezzedine JA, Uwizeye C, Si Larbi G, Villain G, Louwagie M, Schilling M, Hagenmuller P, Gallet B, Stewart A, Petroutsos D, Devime F, Salze P, Liger L, Jouhet J, Dumont M, Ravanel S, Amato A, Valay JG, Jouneau PH, Falconet D, and Maréchal E
Adaptive Traits of Cysts of the Snow Algae
Sanguina nivaloides Unveiled by 3D Subcellular Imaging.
Nature Communications, 2023.