AB 22:95-110 (2014)  -  DOI: https://doi.org/10.3354/ab00586

Light acclimation and pH perturbations affect photosynthetic performance in Chlorella mass culture

Sven Ihnken1,*, John Beardall2, Jacco C. Kromkamp1, Cintia Gómez Serrano3, Moacir A. Torres4, Jiří Masojídek5, Irene Malpartida3, Robert Abdala3, Celia Gil Jerez3, Jose R. Malapascua5, Enrique Navarro6, Rosa M. Rico3, Eduardo Peralta3, João P. Ferreira Ezequil6,7, Félix Lopez Figueroa3

1Royal Netherlands Institute for Sea Research (NIOZ), PO Box 140, 4400 AC Yerseke, The Netherlands
2School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
3Departamento de Ecología, Facultad de Ciencias, Universidad de Málaga, Campus Universitario de Teatinos s/n, 29071 Málaga, Spain
4Departamento de Bioquímica, Institute de Química, Unversidade de São Paulo, SP, Brazil
5Institute of Microbiology, Academy of Sciences, 37981 Trebon, Czech Republic
6Pyrenean Institute of Ecology (CSIC), Av. Montañana 1005, Zaragoza 50059, Spainl
7Departamento de Biologia, Universidade de Aveiro, Aveiro 3810-193, Portugal
*Corresponding author:

ABSTRACT: Chlorella spp. are robust chlorophyte microalgal species frequently used in mass culture. The pH optimum for growth is close to neutrality; at this pH, theoretically little energy is required to maintain homeostasis. In the present study, we grew Chlorella fusca cells in an open, outdoor, thin-layer cascade photobioreactor (TLC), under ambient photon flux at the theoretically preferred pH (7.2), and let the culture pass the exponential growth phase. Using pH drift experiments, we show that an alkalization to pH 9 supported photosynthesis in the TLC. The increased photosynthetic activity under alkaline conditions was a pH-dependent effect, and not a dissolved inorganic carbon (DIC) concentration- or light intensity-dependent effect. Re-acidification (in one step or in increments) lowered gross oxygen production and increased non-photochemical quenching in short-term experiments. Gross oxygen production and electron transport rates in PSII were uncoupled during the pH perturbation experiments. Electron transport rates were only marginally affected by pH, whereas oxygen production rates decreased with acidification. Alternative electron pathways, electron donation at the plastid terminal oxidase and state-transitions are discussed as a potential explanation. Because cell material from the TLC was not operating at maximal capacity, we propose that alkalization can support photosynthesis in challenged TLC systems.

KEY WORDS: Chlorella · Mass culture · pH perturbance · Chlorophyll fluorescence · Oxygen production · pH drift · Photosynthesis · Photoprotection

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Cite this article as: Ihnken S, Beardall J, Kromkamp JC, Gómez Serrano C and others (2014) Light acclimation and pH perturbations affect photosynthetic performance in Chlorella mass culture. Aquat Biol 22:95-110. https://doi.org/10.3354/ab00586

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