In terrestrial plants, photo- and thermoacclimation appear to be triggered by fluctuations in the redox state of the plastoquinone pool (PQ pool) in chloroplasts, with putative coadjutant participation of hydrogen peroxide (H₂O₂), ascorbate and glutathione pools. Excess amounts of chloroplast-originated H₂O₂ severely inactivate housekeeping hemeproteins, including those involved in photosynthesis. Under biotic/abiotic stresses, red seaweeds of the genus Kappaphycus and Eucheuma release massive amounts of H₂O₂ into the surrounding seawater in order to prevent peroxide accumulation within algal tissues. Thus, the aim of this work was to study the kinetic decay of the plastoquinone (PQ) pool availability in the red alga Kappaphycus alvarezii under single or combined effects of high light, low temperature, and sub-lethal doses of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), inhibitors of the thylakoid electron transport system. The PQ pool availability was estimated by integrating the area over chlorophyll fluorescence induction curves of algal samples (Fo-Fm transition). Within 24 h, high light and chilling stresses distinctly affected the availability of the PQ pool for photosynthesis following second-order polynomial and exponential functions, respectively. On the other hand, the combined harmful stimuli were all fitted by exponential decays of the PQ pool availability in the chloroplasts of algal samples. The moderate correlation index (R = 0.673) found between the PQ pool availability (after 24 h) and H₂O₂ concentrations in the seawater suggests that both single or combined stimuli applied here dramatically affected the redox stoichiometry in the thylakoids, leading to higher H₂O₂ production from algal cells. Membrane fluidity and intermolecular collisions, as well-established thermo-dependent events that limit the mobility of diffusible electron carriers as PQ and plastocyanin, could explain the synergistic effect observed on PQ pool availability by combining chilling stress with high light or DCMU/DBMIB treatments.