Unrecognized controls on microbial functioning in Blue Carbon ecosystems: the role of mineral enzyme stabilization and allochthonous substrate supply

Tidal wetlands are effective carbon sinks, mitigating climate change through the long-term removal of atmospheric CO2. Studies along surface-elevation and thus flooding-frequency gradients in tidal wetlands are often used to understand the effects of accelerated sea-level rise on carbon sequestration, a process that is primarily determined by the balance of primary production and microbial decomposition. It has often been hypothesized that rates of microbial decomposition would increase with elevation and associated increases in soil oxygen availability; however, previous studies yield a wide range of outcomes and equivocal results. Our mechanistic understanding of the elevation-decomposition relationship is limited because most effort has been devoted to understanding the terminal steps of the decomposition process. Few studies assessed microbial exo-enzyme activities (EEAs) as initial and rate-limiting steps that often reveal important insight into microbial energy and nutrient constr...