Microbial abundance and activity of nitrite/nitrate-dependent anaerobic methane oxidizers in estuarine and intertidal wetlands: Heterogeneity and driving factors

Nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) is a crucial link between carbon and nitrogen cycles in estuarine and coastal ecosystems. However, the factors that affect the heterogeneous variability in n-DAMO microbial abundance and activity across estuarine and intertidal wetlands remain unclear. This study examined the spatiotemporal variations in n-DAMO microbial abundance and associated activity in different estuarine and intertidal habitats via quantitative PCR and C-13 stable isotope experiments. The results showed that Candidatus 'Methylomirabilis oxyfera' (M. oxyfera)-like DAMO bacteria and Candidatus 'Methanoperedens nitroreducens' (M. nitroreducens)-like DAMO archaea cooccurred in estuarine and intertidal wetlands, with a relatively higher abundance of the M. oxyfera-like bacterial pmoA gene (4.0 x 10(6)-7.6 x 10(7) copies g(-1) dry sediment) than the M. nitroreducens-like archaeal mcrA gene (4.5 x 10(5) -9.4 x 10(7) copies g(-1) dry sediment). The abundance of the M. oxyfera-like bacterial pmoA gene was closely associated with sediment pH and ammonium (P<0.05), while no significant relationship was detected between M. nitroreducens-like archaeal mcrA gene abundance and the measured environmental parameters (P>0.05). High n-DAMO microbial activity was observed, which varied between 0.2 and 84.3 nmol (CO2)-C-13 g(-1) dry sediment day(-)1 for nitrite-DAMO bacteria and between 0.4 and 32.6 nmol (CO2)-C-13 g(-1) dry sediment day(-1) for nitrate-DAMO archaea. The total n-DAMO potential tended to be higher in the warm season and in the upstream freshwater and low-salinity estuarine habitats and was significantly related to sediment pH, total organic carbon, Fe(II), and Fe(III) contents (P<0.05). In addition to acting as an important methane (CH4) sink, n-DAMO microbes had the potential to consume a substantial amount of reactive N in estuarine and intertidal environments, with estimated nitrogen elimination rates of 0.5-224.7 nmol N g(-1) dry sediment day(-1). Overall, our investigation reveals the distribution pattern and controlling factors of n-DAMO bioprocesses in estuarine and intertidal marshes and gains a better understanding of the coupling mechanisms between carbon and nitrogen cycles. (c) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study revealed the distribution pattern and controlling factors of nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) bioprocesses in estuarine and intertidal marshes. It showed that Candidatus 'Methylomirabilis oxyfera'-like DAMO bacteria and Candidatus 'Methanoperedens nitroreducens'-like DAMO archaea cooccurred, with higher abundance of the M. oxyfera-like bacteria and a positive correlation with sediment pH and ammonium content.