Objective The ocean, as the largest “active” carbon reservoir on Earth, plays a critical role in global carbon cycling. Macroalgae contribute to this process through photosynthetic carbon fixation and the release of dissolved organic carbon (DOC) and particulate organic carbon (POC) via physiological metabolism. Harnessing the carbon sequestration potential of macroalgae represents a vital pathway toward achieving the "carbon neutrality" goal.

Progress This review comprehensively examines the mechanisms by which macroalgae enhance carbon sequestration, including the synthesis of biomass carbon through photosynthesis and the release of DOC and POC. We summarize methods for assessing “short-term carbon sinks” based on macroalgae cultivation yields, as well as techniques for evaluating "long-term carbon sinks," such as the C/N ratio, stable isotope analysis, multi-omics technologies, and relevant model construction, etc. Additionally, we analyze the impacts of key environmental factors including temperature, nutrient concentration, light intensity, salinity, and desiccation on the growth of macroalgae and their photosynthetic carbon fixation efficiency.

Prospect By providing a multi-faceted perspective on the carbon sink function, carbon sequestration mechanisms, assessment methods, and environmental factors influencing macroalgae, this review aims to deepen the understanding of their critical role in marine carbon sinks and to offer foundational insights and references for developing carbon sequestration and enhancement technologies.