Multi-Model and Multi-Scenario Assessment of Macroalgal Blue Carbon Potential: A Case Study of Zhejiang, China

Macroalgae are an important yet underrepresented component of marine blue carbon systems, but regional-scale assessments integrating historical dynamics, environmental drivers, future scenarios, and economic implications remain limited. This study developed an integrated framework to evaluate the macroalgal blue carbon potential of Zhejiang Province, China, a major macroalgal mariculture region. Using multi-source datasets from 2001 to 2023, we analyzed production trends, identified the environmental and socioeconomic factors most strongly associated with production, and projected future production and carbon sequestration under three management scenarios using four predictive approaches. Results showed that macroalgal production increased from 2.83 × 104 tonnes in 2001 to 14.60 × 104 tonnes in 2023, with total mariculture production as the dominant associated socioeconomic factor. Average annual carbon sequestration during 2006–2023 was estimated at 4176 t C (15,327 t CO2 equivalent), increasing rapidly after 2017. Under the baseline scenario, cumulative sequestration during 2023–2042 was projected at approximately 2.67 × 105 t C, while active expansion could raise sequestration potential by approximately 12%. Economic valuation indicated that carbon credits contribute only 0.45–0.76% of product value, insufficient alone to provide a strong economic incentive for large-scale implementation. This study demonstrates the potential of macroalgal mariculture as a nature-based blue carbon solution and provides a transferable framework for coastal carbon management and climate mitigation strategies.