Offshore photovoltaic shading reshapes bloom persistence of the dinoflagellate Prorocentrum donghaiense: Insights from photophysiological and transcriptional regulation.

Offshore photovoltaic (PV) systems increasingly modify coastal light environments, yet their potential influence on harmful algal blooms (HABs) remains unclear. We investigated the physiological and transcriptional responses of the bloom-forming dinoflagellate Prorocentrum donghaiense to simulated PV-induced shading under high (no shading), medium (50%), and low (85%) light conditions. Severe light reduction significantly decreased exponential growth rates but prolonged maintenance of relatively high biomass. Chlorophyll a fluorescence analysis showed stable PSII maximum efficiency (Fv/Fm) across treatments, while low light enhanced relative electron transport (ET0/RC) and reduced energy dissipation (DI0/RC), suggesting enhanced allocation of absorbed energy toward photochemical processes. Transcriptomic analyses revealed global transcriptional downscaling under low light, with relatively maintained expression of genes involved in light harvesting, carbon fixation (particularly C4-like pathways), and material transport. These findings suggest that PV-induced shading may shift P. donghaiense from rapid growth to bloom persistence, highlighting the need to incorporate species-specific responses into offshore PV environmental assessments.