Polystyrene microplastics alter plankton community and enhance greenhouse gas emissions: A case study in the China coastal sea.

Brominated volatile halocarbons (Br-VHCs) emitted from the ocean are the main ozone-depleting substances and greenhouse gases, yet their production dynamics by microorganisms under anthropogenic stressors such as microplastics perturbation are unknown. Here, through coupled ship-based incubations (Yellow Sea) and laboratory experiments, we demonstrate that 1 μm polystyrene (PS) microplastics addition inhibited phytoplankton growth with maximal suppression rates of 82.35% and increased dissolved organic carbon (DOC) accumulation by 91.38%. PS microplastic exposure restructured eukaryotic communities, with Diatoma dominance. Plankton community variation after PS microplastics addition linked to Br-VHCs production, with Arcocellulus (phytoplankton) and Pseudophaeobacter (bacteria) as keystone taxa to explain Br-VHCs variance. Under PS treatment, Br-VHCs emissions increased by up to 36.89%, driven by oxidative stress (ROS levels 4.15-fold higher than controls) and DOC accumulation, mechanistically related to H₂O₂-mediated halogenation. These findings reveal plastic pollution is a catalytic force in marine halogen biogeochemistry, highlighting the reassessment of oceanic climate feedbacks under anthropogenic forcing.