Denitrifying anaerobic methane oxidation in marsh sediments of Chongming eastern intertidal flat

Denitrifying anaerobic methane oxidation (DAMO) and associated microbial diversity and abundance in the marsh sediments of Chongming eastern intertidal flat, the Yangtze Estuary, were investigated using carbon-isotope tracing and molecular techniques. Co-existence of nitrate-DAMO archaea and nitrite-DAMO bacteria was evidenced, with higher biodiversity of DAMO archaea than DAMO bacteria. Abundance of DAMO archaeal mcrA gene and DAMO bacterial pmoA gene ranged from 4.2 × 10³ to 3.9 × 10¹⁰ copies g^-1 and from 4.5 × 10⁵ to 6.4 × 10⁶ copies g^-1, respectively. High DAMO potential was detected, ranging from 0.6 to 46.7 nmol ¹³CO₂ g^-1 day^-1 for nitrate-DAMO and from 1.3 to 39.9 nmol ¹³CO₂ g^-1 day^-1 for nitrite-DAMO. In addition to playing an important role as a CH₄ sink, DAMO bacteria also removed a substantial amount of reactive nitrogen (29.4 nmol N g^-1 day^-1) from the intertidal sediments. Overall, these results indicate the importance of DAMO bioprocess as methane and nitrate sinks in intertidal marshes.