Fast-growing Arctic Fe–Mn deposits from the Kara Sea as the refuges for cosmopolitan marine microorganisms

Abstract

The impact of biomineralization and redox processes on the formation and growth of ferromanganese deposits in the World Ocean remains understudied. This problem is particularly relevant for the Arctic marine environment where sharp seasonal variations of temperature, redox conditions, and organic matter inflow significantly impact the biogenic and abiotic pathways of ferromanganese deposits formation. The microbial communities of the fast-growing Arctic Fe–Mn deposits have not been reported so far. Here, we describe the microbial diversity, structure and chemical composition of nodules, crust and their underlying sediments collected from three different sites of the Kara Sea. Scanning electron microscopy revealed a high abundance of microfossils and biofilm-like structures within the nodules. Phylogenetic profiling together with redundancy and correlation analyses revealed a positive selection for putative metal-reducers (Thermodesulfobacteriota), iron oxidizers (Hyphomicrobiaceae and Scalinduaceae), and Fe-scavenging Nitrosopumilaceae or Magnetospiraceae in the microenvironments of the Fe–Mn deposits from their surrounding benthic microbial populations. We hypothesize that in the Kara Sea, the nodules provide unique redox-stable microniches for cosmopolitan benthic marine metal-cycling microorganisms in an unsteady environment, thus focusing the overall geochemical activity of nodule-associated microbial communities and accelerating processes of ferromanganese deposits formation to uniquely high rates.

Morphology‐Dependent Magnetic Properties in Shallow‐Water Ferromanganese Concretions

“…In general, members of the Nitrospirae phylum or Deltaproteobacteria class tend to synthesize asymmetric crystals, often with kinked or bullet‐shaped morphologies. Both Nitrospirae and Deltaproteobacteria have been described in shallow sea Fe‐Mn concretions (Shulga et al., 2022; Yli‐Hemminki et al., 2014).…”

Ostracod Assemblages in the East Siberian Sea: A Comparative Study of River-Influenced and River-Isolated Shelf Ecosystems

“…It seems the rusty crusts from our ostracod individuals consist of iron compounds whereas the black spots and crusts contain the manganese oxides. Possibly they form near the sediment-water interface during the bacterial processes, similarly to the formation of the ferromanganese nodule field, which is widely distributed in the Arctic, e.g., [50,51]. The presence of diatom communities on the surface valves is typical of the shallow-water ostracods [52].…”