Rapid evolution of marine phytoplankton under global change: mechanisms, constraints, and ecological consequences

Marine phytoplankton are the foundation of oceanic food webs and play a pivotal role in global carbon cycling. As climate change accelerates, rising temperatures, ocean acidification, and nutrient stress impose unprecedented selective pressures on these organisms. Emerging evidence from experimental evolution, genomic studies, and modeling suggests that phytoplankton can undergo rapid adaptation over ecological timescales. Here, we synthesize current knowledge on the mechanisms of rapid evolution in marine phytoplankton, including phenotypic plasticity, standing genetic variation, and polyploidization. We highlight the interplay between short-term plastic responses and long-term genetic adaptation, and explore how these processes are constrained by metabolic trade-offs and evolutionary limits. Furthermore, we examine the ecological and biogeochemical consequences of rapid evolution, emphasizing feedbacks to primary production and global biogeochemical cycles. Finally, we discuss emerging methodological frameworks for predicting evolutionary responses under multi-stressor scenarios and propose key research priorities to integrate evolutionary dynamics into global change models.