Processes affecting soil organic carbon persistence in blue carbon ecosystems – a quantitative literature review

Blue carbon ecosystems are among the most efficient carbon sinks on Earth. They are situated at the interface between land and sea, and include salt marshes, mangroves and seagrass meadows. Despite the importance of the underground soil organic carbon (SOC) stabilization in these ecosystems, the mechanisms influencing SOC accrual and release are poorly understood. The aim of this study was to disentangle the complex interplay between organic substrates, microorganisms, environmental conditions (e.g., temperature, moisture) and soil physicochemical properties to investigate the importance of stabilization mechanisms identified in terrestrial environments in these systems.

To this end a systematic literature review was conducted to quantify SOC pools in those blue carbon ecosystems including particulate organic matter (POM), mineral-associated organic matter (MAOM) and dissolved organic matter (DOM), which may differ significantly in their formation processes, chemical composition, persistence and ecological functions.

In particular, we investigated the importance of MAOM in blue carbon systems and the factors influencing its formation and release in these systems. We hypothesized that it might not be as persistent as in terrestrial systems. Moreover, we hypothesized that oxygen availability, redox dynamics and salinity are most probably major controlling factors in the sequestration and long-term stabilization of blue carbon.

An initial literature assessment identified on the order of 300 relevant publications on MAOM in blue carbon ecosystems, including 150 focusing on mangroves, 100 on salt marshes and 50 on seagrass meadows.