| Abstract: |
Freshwater algae sustain aquatic food webs and increasingly serve as biological platforms for wastewater polishing and biomass production, yet their biochemical stability is challenged by warming, excess irradiance, and Stalinization. This empirical study quantified the response of Chlorella vulgaris to high light (450 µmol photons m⁻² s⁻¹), heat (34 °C), salinity (100 mM NaCl), and their combined exposure over 12 d. Triplicate batch cultures were compared with a 25 °C, 100 µmol photons m⁻² s⁻¹ control. Biomass, chlorophyll a, maximum photo system-II efficiency (Fv/Fm), reactive oxygen species (ROS), malondialdehyde (MDA), and antioxidant enzymes were measured on days 0, 3, 6, 9, and 12; a 72-h common-garden recovery test evaluated reversibility. Single stressors reduced terminal biomass by 19–43%, whereas combined stress reduced it by 71%. The combined treatment increased ROS 3.9-fold and MDA 2.5-fold, accompanied by elevated superoxide dismutase, catalase, and ascorbate peroxidase [1]. Chlorophyll a and Fv/Fm declined strongly, and their inverse association with ROS supported oxidative damage as a proximate constraint on photosynthesis. Antioxidant activation moderated injury under isolated stress but was insufficient under the multi-stressor regime. Recovery restored 55–91% of control biomass under single stress, while combined-stress cultures remained at 42%, indicating lasting impairment [2]. These data link environmental drivers to a coherent sequence of redox imbalance, membrane damage, photochemical loss, and reduced production. The results underscore that risk assessments based on one stressor can overestimate algal resilience in warming, ion-enriched freshwaters [3]. |
