How do microalgae perceive light in a high-rate pond? Towards more realistic Lagrangian experiments

Type Article
Date 2018-05
Language English
Author(s) Demory David1, 2, 3, Combe Charlotte1, 2, 3, Hartmann Philipp1, 2, 3, Talec Amelle1, 3, Pruvost Eric1, 3, Hamouda Raouf4, Souille Fabien4, Lamarea Pierre-Olivier2, 4, Bristeau Marie-Odile4, Sainte-Marie Jacques4, Rabouille Sophie1, 3, Mairet FrancisORCID2, 5, Sciandra Antoine1, 2, 3, Bernard Olivier1, 2, 3
Affiliation(s) 1 : UPMC Univ Paris 06, Sorbonne Univ, LOV, Observ Oceanol,UMR 7093, F-06230 Villefranche Sur Mer, France.
2 : Univ Cote Azur, INRIA, BIOCORE, BP93, F-06902 Sophia Antipolis, France.
3 : CNRS, LOV, Observ Oceanol, UMR 7093, F-06230 Villefranche Sur Mer, France.
4 : INRIA Paris, Team Ange, 2 Rue Simone Iff,CS 42112, F-75589 Paris 12, France.
5 : IFREMER, PBA, F-44311 Nantes, France.
Source Royal Society Open Science (2054-5703) (Royal Soc), 2018-05 , Vol. 5 , N. 5 , P. 180523 (14p.)
DOI 10.1098/rsos.180523
WOS© Times Cited 21
Keyword(s) photosynthesis, hydrodynamics, modelling, photoacclimation, Dunaliella salina, non-photochemical quenching

Hydrodynamics in a high-rate production reactor for microalgae cultivation affects the light history perceived by cells. The interplay between cell movement and medium turbidity leads to a complex light pattern, whose forcing effects on photosynthesis and photoacclimation dynamics are nontrivial. Hydrodynamics of high density algal ponds mixed by a paddle wheel has been studied recently, although the focus has never been on describing its impact on photosynthetic growth efficiency. In this multidisciplinary downscaling study, we first reconstructed single cell trajectories in an open raceway using an original hydrodynamical model offering a powerful discretization of the Navier-Stokes equations tailored to systems with free surfaces. The trajectory of a particular cell was selected and the associated high-frequency light pattern was computed. This light pattern was then experimentally reproduced in an Arduino-driven computer controlled cultivation system with a low density Dunaliella salina culture. The effect on growth and pigment content was recorded for various frequencies of the light pattern, by setting different paddle wheel velocities. Results show that the frequency of this realistic signal plays a decisive role in the dynamics of photosynthesis, thus revealing an unexpected photosynthetic response compared to that recorded under the on/off signals usually used in the literature. Indeed, the light received by a single cell contains signals from low to high frequencies that nonlinearly interact with the photosynthesis process and differentially stimulate the various time scales associated with photoacclimation and energy dissipation. This study highlights the need for experiments with more realistic light stimuli to better understand microalgal growth at high cell densities. An experimental protocol is also proposed, with simple, yet more realistic, step functions for light fluctuations.

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Demory David, Combe Charlotte, Hartmann Philipp, Talec Amelle, Pruvost Eric, Hamouda Raouf, Souille Fabien, Lamarea Pierre-Olivier, Bristeau Marie-Odile, Sainte-Marie Jacques, Rabouille Sophie, Mairet Francis, Sciandra Antoine, Bernard Olivier (2018). How do microalgae perceive light in a high-rate pond? Towards more realistic Lagrangian experiments. Royal Society Open Science, 5(5), 180523 (14p.). Publisher's official version : , Open Access version :