Spatial and seasonal distributions of Feammox from ecosystem habitats in the Wanshan region of the Taihu watershed, China

Abstract Anaerobic ammonium oxidation coupled to Fe(III) reduction, termed Feammox, is a newly identified microbial process that occurs in nitrogen and iron cycles. As the seasonal distribution of Feammox in different ecosystem habitats has not been fully explored, this study investigated the potential Feammox rates and the diversity and abundance of iron reducing bacteria (IRB) in three habitats during two seasons by using isotope tracing technique and molecular analysis, respectively. Results showed that potential Feammox rates vary both seasonally and spatially, having relatively higher rates in summer (0.05–0.19 mg N kg−1 d−1) and lower rates in winter (0.02–0.09 mg N kg−1 d−1). In addition, relatively higher and lower rates were observed in farmland soils (0.09–0.19 mg N kg−1 d−1) and river sediments (0.02–0.05 mg N kg−1 d−1), respectively. The abundance and diversity of IRB were also found to vary both spatially and seasonally. Furthermore, the results show that Feammox may transform nitrogen at a rate of approximately 2.4–22.5 kg N ha−1 yr−1 within the investigated area. It is considered that the soil moisture, the Fe(III) content, and the total organic carbon are important factors controlling Feammox and IRB. Overall, these results extend current scientific knowledge about nitrogen and iron cycles in ecosystem habitats.