Hidden Diversity of Benthic Filamentous Cyanobacteria: Three Novel Species of Oscillatoriales Discovered in an Underexplored Urban Wetland, Eastern China

Wetlands constitute critical habitats sustaining cyanobacterial diversity. Nevertheless, taxonomic research on wetland benthic filamentous cyanobacteria is far from complete, largely limited by phenotypic plasticity and challenges in strain isolation and cultivation. To unravel the species diversity and taxonomic affiliations of epiphytic cyanobacteria in an urban wetland, cyanobacterial strains were isolated from riparian rocks of the Sanyang Wetland (Zhejiang Province) and characterized via morphological observation, 16S rRNA phylogenetic analysis and 16S–23S ITS structural comparison. Strain WZU 2025, sheathless with occasionally conical apical cells, fell into the genus Kamptonema. It shared less than 97.5% sequence similarity with K. animale and possessed distinctive ITS signatures, hereby proposed as Kamptonema schistus sp. nov. Strain WZU 2023, featuring colorless rigid sheaths and conical apical cells, formed a stable clade with Microcoleus but exhibited distinct ITS structures, and is designated Microcoleus wenzhouensis sp. nov. Strain WZU 2030 bears colourless rigid sheaths and trichomes mostly filled with chromatophores; it clustered reliably with known Wilmottia species yet differed in ITS traits, and is described as Wilmottia sanyangensis sp. nov. Conflicts between morphological taxonomy and molecular phylogeny reveal ambiguous intergeneric relationships within Coleofasciculaceae and Microcoleaceae. The present study expands the known diversity of Microcoleaceae and provides evidence for future taxonomic revisions of cyanobacteria. Combined with the new genus Paludothrix reported from this wetland in 2024, our data demonstrate that cyanobacterial diversity in Sanyang Wetland has been severely underappreciated.