Spatial Resolution of Microbial Community Members Within Cyanobacterial Mats From Temperate Mud Flats.

Benthic cyanobacterial mats (BCMs), known for their high cyanobacterial abundances, are distributed globally across diverse aquatic and semi-aquatic habitats. The microbial composition of BCMs is determined by various environmental factors that regulate key chemical and physical conditions, leading to complex community structures that vary across space and time. Recently, temperate mats have emerged as model systems for studying community structure and nutrient cycling. Using 16S metabarcoding and stable isotope analyses, our study characterized the bacterial members present at a fine-scale resolution across vertical layers of long-standing BCMs from Shackleford Banks Island in North Carolina, USA. Spatially expansive BCMs were mainly composed of Proteobacteria, Bacteroidota, Planctomycetota, Desulfobacterota, Verrucomicrobiota, and Cyanobacteria. Mat communities did not differ along horizontal transects but differed in both the diversity and community composition between vertically stratified layers. Trends in organic matter, carbon, and nitrogen availability match changes in microbial composition and diversity across vertical strata. These findings provided the first molecular characterization of the full bacterial community from BCMs from North Carolina and provide insight into the potential biogeochemical processes within this system.