AUTHOR=Lacour Thomas , Larivière Jade , Ferland Joannie , Bruyant Flavienne , Lavaud Johann , Babin Marcel 

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

JOURNAL=Frontiers in Marine Science

VOLUME=5

YEAR=2018

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2018.00354

DOI=10.3389/fmars.2018.00354

ISSN=2296-7745

ABSTRACT=<p><italic>Thalassiosira gravida</italic> is a major Arctic diatom responsible for the under-ice spring bloom. We investigated <italic>T. gravida</italic> physiological plasticity growing it at two temperatures (0 and 5°C) and under different light intensities typically found in its natural environment. <italic>T. gravida</italic> showed remarkable thermal- and photo-acclimatory plasticity including: low light saturation parameter for growth (K<sub>E</sub>) and photosynthesis (E<sub>K</sub>), low μ<sub>max</sub> but relatively high Chl <italic>a</italic>/C, low C/N, and decreasing light-saturated carbon fixation rate (<inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>P</mml:mtext></mml:mrow><mml:mrow><mml:mtext>m</mml:mtext></mml:mrow><mml:mrow><mml:mtext>C</mml:mtext></mml:mrow></mml:msubsup></mml:math></inline-formula>) with increasing growth irradiance. <italic>T. gravida</italic> 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. <italic>T. gravida</italic> growth remained possible under a wide range of irradiances but photosynthetic plasticity was higher at moderately low light (up to ~50 μmol photons m<sup>−2</sup> s<sup>−1</sup>), nevertheless corresponding to the mean <italic>in situ</italic> 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 <italic>T. gravida</italic> is discussed.</p>