Light-induced fluorescence quenching leads to errors in sensor measurements of phytoplankton chlorophyll and phycocyaninS

WATER RESEARCH

卷:198

Article

Rousso, Benny Zuse^1,2,3  Bertone, Edoardo^1,2,3  Stewart, Rodney A.^1,2  Rinke, Karsten⁴  Hamilton, David P.³ 

[1] Griffith Univ, Griffith Sch Engn & Built Environm, Parklands Dr, Southport, Qld 4222, Australia

[2] Griffith Univ, Cities Res Inst, Parklands Dr, Southport, Qld 4222, Australia

[3] Griffith Univ, Australian Rivers Inst, 170 Kessels Rd, Nathan, Qld 4111, Australia

[4] Helmholtz Ctr Environm Res, Dept Lake Res, Bruckstr 3A, D-39114 Magdeburg, Germany

关键词: Cyanobacteria;    Real-time monitoring;    Fluorescence;    Non-photochemical quenching;    Water resources management;   

DOI  :  10.1016/j.watres.2021.117133

来源: Elsevier

【 摘 要 】

Optical sensors for fluorescence of chlorophyll a (f-Chl a ) and phycocyanin (f-PC) are increasingly used as a proxy for biomass of algae and cyanobacteria, respectively. They provide measurements at highfrequency and modest cost. These sensors require site-specific calibration due to a range of interferences. Light intensity affects the fluorescence yield of cyanobacteria and algae through light harvesting regulation mechanisms, but is often neglected as a potential source of error for in-situ f-Chl a and f-PC measurements. We hypothesised that diel light variations would induce significant f-Chl a and fPC suppression when compared to dark periods. We tested this hypothesis in a controlled experiment using three commercial fluorescence probes which continuously measured f-Chl a and f-PC from a culture of the cyanobacterium Dolichospermum variabilis as well as f-Chl a from a culture of the green alga Ankistrodesmus gracilis in a simulated natural light regime. Under light, all devices showed a significant ( p < 0.01) suppression of f-Chl a and f-PC compared to measurements in the dark. f-Chl a decreased by up to 79% and f-PC by up to 59% at maximum irradiance compared to dark-adapted periods. Suppression levels were higher during the second phase of the diel cycle (declining light), indicating that quenching is dependent on previous light exposure. Diel variations in light intensity must be considered as a significant source of bias for fluorescence probes used for algal monitoring. This is of high relevance as most monitoring activities take place during daytime and hence f-Chl a and f-PC are likely to be systematically underestimated under bright conditions. Compensation models, design modifications to fluorometers and sampling design are discussed as suitable alternatives to overcome light-induced fluorescence quenching. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )

【 授权许可】

Free