Interactive Effects of Nano-Polystyrene and Light Spectra on Growth and Phytohormone (Auxin and Gibberellin) Production in Chlorella vulgaris

This study investigated the intricative effects of nanopolystyrene particles (NPS) and varying light spectra on the growth and phytohormones (auxin and Gibberellin) production in Chlorella vulgaris, a microalgae crucial to aquatic ecosystems, addressing critical aspects of nanoplastic pollution. The algae's physiological and hormonal response was evaluated under varying light spectra (blue, red, and white) and NPS concentrations (5, 10, 20, and 40ppm) over a 23-day period. Results demonstrated that blue light significantly enhanced algae growth rate and increased auxin production, with the highest auxin levels reaches 61.53 μg/g.w. at 5 ppm under blue light on the 20 day. Conversely, red light provides more effective in stimulating gibberellin synthesis, marginally outperforming the blue spectrum. High concentrations of nanopolystyrene (20-40 ppm) consistently inhibited growth and biomass production (e.g. a 15-20 % growth delay under blue light at 40ppm compared to 5ppm) primarily due to oxidative stress and physical shading. Morphological analysis using scanning electron microscope (SEM) revealed significant cellular damage and the accumulation of nanoparticles biofilms on algal cells at 40ppm after 10 days of exposure, visually conforming the physical impact. These finding underscore the complex interplay between specific lighting conditions and neoplastic contamination, high lighting the potential environmental hazards posed by these particles to primary producers in aquatic food webs. The study provides a more profound understanding of the hormonal and physiological adaptable of microalgae to environmental stresses, contributing valuable data to the ongoing discourse on plastic pollution and its ecological consequence.