Fast Repetition Rate Fluorometry (FRRF) Derived Phytoplankton Primary Productivity in the Bay of Bengal

The approach of fast repetition rate fluorometry (FRRF) requires a conversion factor (Φe:C/nPSII) to derive ecologically-relevant carbon uptake rates (PPz,t). However, the required Φe:C/nPSII is commonly measured by 14C assimilation and varies greatly across phytoplankton taxonomy and environmental conditions. Consequently, the use of FRRF to estimate gross primary productivity (GPz,t), alone or in combination with other approaches, has been restricted by both inherent conversion and procedural inconsistencies. Within this study, based on a hypothesis that the non-photochemical quenching (NPQNSV) can be used as a proxy for the variability and magnitude of Φe:C/nPSII, we thus proposed an independent field model coupling with the NPQNSV-based Φe:C/nPSII for FRRF-derived carbon, without the need for additional Φe:C/nPSII in the Bay of Bengal (BOB). Therewith, this robust algorithm was verified by the parallel measures of electron transport rates and 14C-uptake PPz,t. NPQNSV is theoretically caused by the effects of excess irradiance pressure, however, it showed a light and depth-independent response on large spatial scales of the BOB. Trends observed for the maximum quantum efficiency (Fv/Fm), the quantum efficiency of energy conversion (Fq'/Fm') and the efficiency of charge separation (Fq'/Fv') were similar and representative, which displayed a relative maximum at the subsurface and were collectively limited by excess irradiance. In particular, most observed values of Fv/F...
Source: Frontiers in Microbiology - Category: Microbiology Source Type: research