The Role of Sustained Photoprotective Non-photochemical Quenching in Low Temperature and High Light Acclimation in the Bloom-Forming Arctic Diatom Thalassiosira gravida

• Published in: Frontiers in Marine Science
• Main Authors: Lacour, Thomas, Lariviere, Jade, Ferland, Joannie, Bruyant, Flavienne, Lavaud, Johann, Babin, Marcel
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media Sa 2018
• Subjects: Arctic diatom; photosynthesis; sustained NPQ; irradiance; temperature; Arctic
• Online Access: https://archimer.ifremer.fr/doc/00462/57387/59468.pdf; https://archimer.ifremer.fr/doc/00462/57387/59469.pdf; https://doi.org/10.3389/fmars.2018.00354; https://archimer.ifremer.fr/doc/00462/57387/

Thalassiosira gravida is a major Arctic diatom responsible for the under-ice spring bloom. We investigated T. gravida physiological plasticity growing it at two temperatures (0 and 5°C) and under different light intensities typically found in its natural environment. T. gravida showed remarkable thermal- and photo-acclimatory plasticity including: low light saturation parameter for growth (KE) and photosynthesis (EK), low μmax but relatively high Chl a/C, low C/N, and decreasing light-saturated carbon fixation rate (PmC) with increasing growth irradiance. T. gravida also showed remarkable photoprotective features, namely a strong sustained non-photochemical quenching (NPQs, hour kinetics relaxation) supported by a high amount of xanthophyll cycle pigments. T. gravida growth remained possible under a wide range of irradiances but photosynthetic plasticity was higher at moderately low light (up to ~50 μmol photons m−2 s−1), nevertheless corresponding to the mean in situ conditions under which it predominates, i.e., underneath the spring thin-ice punctuated with melting ponds. The potential role of NPQs in the photophysiological plasticity of T. gravida is discussed.