Mapping the optimal marine zones for artificial upwelling and assessing its macroalgae-based carbon sink potential in China

Seaweed aquaculture plays a crucial role in marine food production and carbon sequestration. While artificial upwelling (AU) has been shown to enhance nutrient availability and boost seaweed production in marine ecosystems, the potential of AU-enhanced seaweed cultivation to act as a carbon sink remains poorly understood. Here, we develop a comprehensive framework to estimate the carbon sink potential of AU-enhanced seaweed aquaculture in coastal China. We first quantify environmental suitability for AU projects by creating a composite coefficient (K_AU, unitless) based on engineering constraints. Using the best-performing predictive model among four candidates, we then estimate the additional aquaculture area that could be supported by AU (E_AU). Finally, we combine area-to-yield conversion equations with China’s marine carbon sink accounting method (HY/T 0349–2022) to project carbon sequestration potential. Our analysis identifies suitable AU project sites across 5 provinces, 8 cities, and 11 counties or districts in coastal China. The AU is projected to expand at 3591 km²/yr (2022–2027), representing a 2.5-fold increase over the 2022 baseline, with the expanded areas demonstrating substantial carbon sink capacity (861 656 tonnes/yr), which is equivalent to 99.3 % of the 2022 total. Zhejiang Province emerges as the dominant contributor, accounting for over half of the additional aquaculture area, with Porphyra providing the largest carbon sink contribution. Our quantitative framework provides a foundation for evaluating and optimizing AU deployment strategies for climate change mitigation through marine carbon sinks.