Explicit and implicit assumptions within the blue carbon conceptual model: a critique

Coastal vegetative sub-aquatic ecosystems provide a number of services at both regional and global scales. One such service is atmospheric CO₂ sequestration and storage, referred to as “blue” carbon. The carbon is fixed, trapped and stored within the ecosystems plant biomass and sediments from both autochthonous and allochthonous sources. Current estimates indicate that coastal ecosystems contribute around half of the oceans annual long term carbon storage. However, such calculations contain a number of implicit and explicit assumptions that when challenged can significantly affect the result, namely: (1) assumptions under the umbrella of climatic response at the ecosystem level; (2) assumptions about sedimentary mineralisation; and (3) assumptions about the nature and stability of organic carbon supplied to and formed within the sediments (i.e. black carbon from biomass burning and brown carbon from sedimentary diagenesis).This article briefly reviews the current knowledge and questions these assumptions in light of more recent theories outside current blue carbon literature and measurements of black carbon content across a seagrass meadow.