A definitive blue carbon measurement regime streamlined by discerning suitable novel services

An accurate blue carbon methodology for atmospheric carbon offsets remains elusive, if based solely on changes and export of carbon stocks. Firstly, it is a zero–sum gain to include ex situ organic carbon storage—it is a minor component and difficult to measure. Secondly, no additional sequestration comes from inorganic carbon exports—alkalinity outwelling increases the carbon sequestration of coastal waters while reducing the wetlands’, conversely with dissolved inorganic carbon outwelling. Thirdly, failing to account for allochthonous recalcitrant carbon considerably inflates the wetlands’ carbon sink, as does ignoring respiratory subsidies from partial allochthonous non–refractory mineralisation. Nonetheless, carbon mitigation is enhanced by considering a novel burial service—protection of the remaining allochthonous non–refractory carbon from coastal remineralization. By integrating all these factors relative to the baseline, a practical and parsimonious measurement regime emerges, however, that must also consider the reduction of CO ₂ air–sea fluxes during submersion cycles.