Quantitative Assessment of Carbon Removal Potential of Macroalgae: A Standardized Protocol for Biomass Estimation and...

Macroalgae are an important component of blue carbon systems. However, their carbon removal potential remains difficult to compare across studies because field sampling designs, biomass estimation models, and accounting workflows vary substantially. This study presents a standardized and reproducible protocol for estimating macroalgal biomass and quantifying carbon removal, integrating macroalgal biological traits, marine ecological survey methods, and carbon-cycle accounting principles into a unified workflow. The protocol specifies consistent sampling parameters, harmonized calculation steps, and standardized data recording and reporting to improve cross-study comparability and facilitate regional synthesis. We demonstrate protocol applicability using representative case studies from an offshore kelp community in northern China and a bay sargassum community in southern China, representing contrasting taxa and typical shallow coastal habitats. Using this workflow, within-team relative variability remained below 10%, and cross-team relative error remained below 15%, consistent with established variability thresholds. Overall, the protocol provides an operationally transparent framework for generating comparable macroalgal blue-carbon datasets across sites and research teams, supporting resource surveys and carbon removal assessments.