Phototrophic Carbon Capture in Marine Algae: Comparative Efficiencies, Sequestration Dynamics, and Climate Implications

Algae-based carbon dioxide removal (CDR) systems are increasingly recognized as versatile climate solutions that combine rapid biological uptake with multiple pathways for durable sequestration. Macroalgae and microalgae offer comparative efficiencies that exceed many terrestrial options, while simultaneously contributing to food security, bioeconomic innovation, and ocean stewardship. Yet significant challenges remain in ensuring permanence, developing robust remote monitoring, reporting, and verification (RMRV) frameworks, and integrating algae into carbon markets and policy regimes. Societal acceptance and ethical considerations, including equity, cultural heritage, and governance transparency, will be critical to legitimacy and scale. Future research must advance biological and technological innovation, refine sequestration pathways, and embed social sciences into deployment strategies. Taken together, algae-based systems represent a promising but complex component of the global portfolio of climate mitigation, requiring interdisciplinary collaboration to unlock their full potential and ensure that climate benefits are coupled with broader societal gains.