Photosystem II (PSII) photochemistry is the ultimate source of reducing power for phytoplankton primary productivity (PhytoPP). Single turnover active fluorometry (STAF) provides a non-intrusive method that has the potential to measure PhytoPP on much wider spatiotemporal scales than is possible with more direct methods such as 14C fixation or O2 evolved through water oxidation. LabSTAF is the Chelsea instrument using Single Turnover Active Fluorometry.
Application of a STAF-derived absorption coefficient for PSII light-harvesting (aLHII) provides a method for estimating PSII photochemical flux on a unit volume basis (JVPII). Within this study, we assess potential errors in the calculation of JVPII arising from sources other than photochemically active PSII complexes (baseline fluorescence) and the package effect. Although our data show that such errors can be significant, we identify fluorescence-based correction procedures that can be used to minimize their impact. For baseline fluorescence, the correction incorporates an assumed consensus PSII photochemical efficiency for dark-adapted material.
The error generated by the package effect can be minimized through the ratio of variable fluorescence measured within narrow wavebands centered at 730 nm, where the re-absorption of PSII fluorescence emission is minimal, and at 680 nm, where re-absorption of PSII fluorescence emission is maximal. We conclude that, with incorporation of these corrective steps, STAF can provide a reliable estimate of JVPII and, if used in conjunction with simultaneous satellite measurements of ocean color, could take us significantly closer to achieving the objective of obtaining reliable autonomous estimates of PhytoPP.
Phytoplankton monitoring using Single Turnover Active Fluorometry
Phytoplankton photosynthetic physiology can be investigated through single turnover active fluorometry (STAF) approaches, which carries the unique potential to autonomously collect data at high spatial and temporal resolutions. Chelsea Technologies’ LabSTAF is a new generation fluorometer that uses single turnover active fluorometry to measure very low levels of photosynthesis, ideal for oligotrophic zonesLabSTAF is the world’s leading portable instrumentation option for Phytoplankton primary productivity.
- Benchtop instrument to measure primary productivity using fluorescence, giving data for over 50 useful parameters within 15 minutes
- LabSTAF includes a peristaltic pump, solenoid unit and flow-through stirrer unit to provide for mixing, sample exchange and a periodic cleaning cycle.
- Data from LabSTAF is interpreted and analysed internally in the included Surface Go