Toward autonomous measurements of photosynthetic electron transport rates: An evaluation of active fluorescence‐based measurements of photochemistry

Abstract

This study presents a methods evaluation and intercalibration of active fluorescence-based measurements of the quantum yield (/ 0 PSII ) and absorption coefficient (a PSII ) of photosystem II (PSII) photochemistry. Measurements of / 0 PSII , a PSII , and irradiance (E) can be scaled to derive photosynthetic electron transport rates (P e ), the process that fuels phytoplankton carbon fixation and growth. Bio-optical estimates of / 0 PSII and a PSII were evaluated using 10 phytoplankton cultures across different pigment groups with varying bio-optical absorption characteristics on six different fast-repetition rate fluorometers that span two different manufacturers and four different models. Culture measurements of / 0 PSII and the effective absorption cross section of PSII photochemistry (r PSII , a constituent of a PSII ) showed a high degree of correspondence across instruments, although some instrument-specific biases are identified. A range of approaches have been used in the literature to estimate a PSII ðkÞ and are evaluated here. With the exception of ex situ a PSII ðkÞ estimates from paired r PSII and PSII reaction center concentration (½RCII) measurements, the accuracy and precision of in situ a PSII ðkÞ methodologies are largely determined by the variance of method-specific coefficients. The accuracy and precision of these coefficients are evaluated, compared to literature data, and discussed within a framework of autonomous P e measurements. This study supports the application of an instrument-specific calibration coefficient (K R ) that scales minimum fluorescence in the dark (F 0 ) to a PSII as both the most accurate in situ measurement of a PSII , and the methodology best suited for highly resolved autonomous P e measurements.V C 2014 Association for the Sciences of Limnology and Oceanography Improved monitoring of phytoplankton productivity (PP) is a core goal across the aquatic sciences and underpins long term management plans for coastal seas and the global ocean (European Marine Board 2013). Following the success of global ocean observatory systems such as the free-drifting Argo profilers (http://www.argo.ucsd.edu/), scientists are now looking to integrate instruments that are capable of autonomous biological rate and flux measurements into environmental sensor networks (Claustre et al. 2010). Unlike traditional in vitro photosynthetic assays, active fluorescence-based photosynthetic measurements are well suited for environmental sensor networks as many of these optical instruments can operate autonomously providing high resolution in situ photosynthesis measurements. Bio-optical models scale active fluorescence measurements to generate estimates of electron transport rates by photosystem II (P e ), whose reductant yield fuels carbon fixation and growth. The derivation of P e is shown in Eq. 1 as the product of photon irradiance (EðkÞ), the absorption coefficient of photosystem II (PSII) light-harvesting pigments (a LHII ðkÞ), and E-dependent measurements of the quantum yield of PSII pho...

Arctic Micromonas uses protein pools and non-photochemical quenching to cope with temperature restrictions on Photosystem II protein turnover

“…Oxborough et al (2012) and Silsbe et al (2015) introduced F 0 ′/ σ PSII ′ as a rapid measure of [PSII] active with calibration against slower oxygen flash yield measures (Chow et al 1989; Suggett et al 2009) of [PSII] active . We found good correlation between F 0 ′/ σ PSII ′ and oxygen flash yield measures of [PSII] active for culture samples taken direct from growth conditions.…”

Variation of the photosynthetic electron transfer rate and electron requirement for daily net carbon fixation in Ariake Bay, Japan

“…The technique has been widely considered a key milestone in aquatic research for global efforts to understand environmental regulation of primary productivity since the data can be acquired over unprecedented time and space scales, and with a resolution far beyond that from conventional incubation methods (Suggett et al 2009a). While FRRf has been principally applied to phytoplankton studies examining the effects of physiological stress, such as nutrient limitation (e.g., Behrenfeld and Kolber 1999;Moore et al 2006Moore et al , 2008, it has also been utilized for characterization light absorption (Suggett et al 2004;Silsbe et al 2015) and for interpreting Abstract Fast repetition rate fluorometry (FRRf) provides a potential means to examine marine primary productivity; however, FRRf-based productivity estimations require knowledge of the electron requirement (K) for carbon (C) uptake (K C ) to scale an electron transfer rate (ETR) to the CO 2 uptake rate. Most previous studies have derived K C from parallel measurements of ETR and CO 2 uptake over relatively short incubations, with few from longerterm daily-integrated periods.…”

Phytoplankton σPSII and Excitation Dissipation; Implications for Estimates of Primary Productivity

“…phytoplankton primary productivity and acclimation (Suggett et al, 2003(Suggett et al, , 2004(Suggett et al, , 2009Oxborough et al, 2012;Silsbe et al, 2015).…”