Abstract

Ocean acidification, driven primarily by increased atmospheric CO2 levels, poses a significant threat to marine ecosystems, particularly phytoplankton communities, which form the foundation of the oceanic food web. As the pH of seawater decreases, the physiological and ecological dynamics of phytoplankton are altered, affecting their growth, composition, and nutrient cycling. This review examines the various mechanisms through which ocean acidification impacts phytoplankton, including changes in photosynthetic efficiency, calcification rates, and interspecific competition. It also highlights the differential responses of various phytoplankton taxa, revealing potential shifts in community structure and functionality that could have cascading effects on higher trophic levels and overall ocean productivity. Furthermore, the implications for biogeochemical cycles, such as carbon and nitrogen cycling, are discussed in the context of a changing ocean. This synthesis emphasizes the urgent need for further research into the long-term effects of ocean acidification on phytoplankton communities, as well as the importance of implementing mitigation strategies to preserve these vital organisms and the ecosystems they support.