What is it about?

Based on field data from a mangrove in southeast Queensland, Australia, we used a structural equation model to elucidate (1) the biotic and abiotic drivers of surface sediment organic carbon (SOC) (10 cm) and sediment CO2 flux; (2) the effect of SOC on sediment CO2 flux; and (3) the covariation among the environmental drivers assessed. Sediment water content, the percentage of fine-grained sediment (b63 μm), surface sediment chlorophyll and light condition collectively drive sediment CO2flux, explaining 41%of their variation. Sediment water content, the percentage of fine sediment, season, land- form setting, mangrove species, sediment salinity and chlorophyll collectively drive surface SOC, explaining 93% of its variance. Sediment water content and the percentage of fine sediment have a negative impact on sediment CO2 flux but a positive effect on surface SOC content, while sediment chlorophyll is a positive driver of both.

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Why is it important?

Despite numerous studies examining the factors that independently influence SOC stock and CO2 flux, the relationships among SOC stock, sediment CO2 flux and their drivers have not been analysed in one comprehensive model. It is important to explore the relationships in a single analysis because identifying the relative weight of drivers of both SOC stock and sediment CO2 flux would provide insights into effective blue C management. This study fills the knowledge gap.

Perspectives

This study provides clues on facilitating blue C management from the perspective of SOC content and CO2 efflux. Initiatives on mangrove restoration and rehabilitation should be cautious when habitats are dominated by high proportions of coarse particles (e.g. sand and gravels),which promote sediment CO2 efflux and hamper SOC storage, as does low sediment water content. Sediment surface microphytobenthos may enhance both SOC content and CO2 efflux, and is neutral to blue C management. Future studies are expected to involve more belowground processes in the structural equation modelling.

PhD Xiaoguang Ouyang
Chinese University of Hong Kong

Read the Original

This page is a summary of: Structural equation modelling reveals factors regulating surface sediment organic carbon content and CO2 efflux in a subtropical mangrove, The Science of The Total Environment, February 2017, Elsevier, DOI: 10.1016/j.scitotenv.2016.10.218.
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