kurokawa

Mt. Aso is an active volcano located in Kumamoto, Japan. Kurokawa river in the Aso area was influenced by groundwater with high Fe and Mn concentration and associated orange deposits in the upstream and black thick crusts (Maximum: 3 cm) on the wall of waterway tunnel located in the midstream regions. In this study, orange deposits, crusts, and river water were analyzed via chemical and molecular biological methods to elucidate the mechanism underlying crust formation. X-ray fluorescence analysis revealed orange deposits containing about 45% as Fe2O3 and a black crust primarily comprising 20-27% as MnO and 13~16% as Fe2O3, respectively. Microbial communities in orange deposits, black crusts, and river water were analyzed using molecular biology techniques. Sequencing analysis revealed that orange deposits contained a high ratio of iron-oxidizing bacteria Gallionella sp. In contrast, black crust displayed greater microbial diversity with a higher ratio of several microbes including Sphingomonas Hyphomicrobium Nitrospira, previously reported Mn-crusts or nodules in marine and freshwater environment.