Electron donors and acceptors influence anaerobic soil organic matter mineralization in tidal marshes

► On a per gram soil basis, brackish soils had higher microbial respiration (CO2 + CH4 produced). ► On a per gram carbon basis, however, respiration was greater in the freshwater soils. ► Anaerobic carbon mineralization was higher for both soil types incubated at the brackish site. ► Thermodynamically favorable terminal electron acceptors stimulated carbon mineralization.