Microbial Diversity of Deep-Sea Ferromanganese Crust Field in the Rio Grande Rise, Southwestern Atlantic Ocean

Abstract

AbstractSeamounts are often covered with Fe and Mn oxides, known as ferromanganese (Fe-Mn) crusts. Future mining of these crusts is predicted to have significant effects on biodiversity in mined areas. Although microorganisms have been reported on Fe–Mn crusts, little is known about the role of crusts in shaping microbial communities. Here, we investigated microbial community based on 16S rRNA gene sequences retrieved from Fe-Mn crusts, coral skeleton, calcarenite and biofilm at crusts of the Rio Grande Rise (RGR). RGR is a prominent topographic feature in the deep southwestern Atlantic Ocean with Fe-Mn crusts. Our results revealed that crust field of the RGR harbors a usual deep-sea microbiome. We observed differences of microbial structure according to the sampling location and depth, suggesting an influence of water circulation and availability of particulate organic matter. Bacterial and archaeal groups related to oxidation of nitrogen compounds, such as Nitrospirae, Nitrospinae phyla, Nitrosopumilus within Thaumarchaeota group were present on those substrates. Additionally, we detected abundant assemblages belonging to methane oxidation, i. e. Ca. Methylomirabilales (NC10) and SAR324 (Deltaproteobacteria). The chemolithoautotrophs associated with ammonia-oxidizing archaea and nitrite-oxidizing bacteria potentially play an important role as primary producers in the Fe-Mn substrates from RGR. These results provide the first insights into the microbial diversity and potential ecological processes in Fe-Mn substrates from the Atlantic Ocean. This may also support draft regulations for deep-sea mining in the region.