Iron-Rich Wetland Environments in Chilean Patagonia: Hydrochemical and Microbial Evidence for Potential Iron–Nitrogen Coupling

Iron-rich aquatic environments can support redox processes that couple the iron and nitrogen cycles, but these interactions remain poorly characterized in Patagonian wetlands. This study investigated the hydrochemical and microbial characteristics of iron-rich environments in the Exploradores Valley, Chilean Patagonia, and assessed their potential to support coupled Fe-N transformations. Historical monitoring data from six rivers in the General Carrera sector were analyzed to establish the regional context for Fe, complemented by PHREEQC equilibrium modeling. Water and sediments from four wetland environments in the site were characterized physicochemically, and microbial communities from two contrasting Fe-rich sites were analyzed using 16S rRNA gene sequencing. Regional records revealed strong spatial variability in total Fe. The sites in Explorers Valley showed marked differences in Fe, organic matter, and nitrogen species, along with visible Fe-rich deposits and conditions favorable for redox stratification. Microbial communities contained taxa associated with Fe oxidation and reduction, as well as nitrogen transformations, including Gallionellaceae, Geobacteraceae, Nitrosomonadaceae, Gallionella, Rhodoferax, and Anaeromyxobacter. These findings identify the Explorers Valley wetlands as naturally Fe-rich systems with microbial and geochemical conditions potentially favorable for the coupled iron–nitrogen cycle, laying the groundwork for future direct investigations of Feammox and NDFO.