Development of photosynthetic carbon fixation model using multi-excitation wavelength fast repetition rate fluorometry in Lake Biwa

Direct measurements of gross primary productivity (GPP) in the water column are essential, but can be spatially and temporally restrictive. Fast repetition rate fluorometry (FRRf) is a bio-optical technique based on chlorophyll (Chl- ) fluorescence that estimate electron transport (ETR PSII at photosystem II (PSII) phytoplankton real time. However, derivation GPP carbon units from ETR remains challenging because requirement for fixation (? e,C ), which mechanistically 4 mol e ? C ?1 or above, vary depending multiple factors. In addition, FRRf studies limited freshwater lakes where phosphorus limitation cyanobacterial blooms common. The goal present study to construct robust ? model ecosystems using simultaneous by with multi-excitation wavelengths coupled traditional 13 method. was conducted oligotrophic mesotrophic parts Lake Biwa July 2018 May 2019. combination excitation light 444, 512 633 nm correctly estimated cyanobacteria. apparent range community 1.1–31.0 during period. A generalised linear showed best fit including 12 physicochemical biological factors explained 67% variance . Among all factors, temperature most significant, while photosynthetically active radiation intensity not. This quantifies situ method ecosystem, discusses core issues methodology calculate , assesses applicability lake prediction.