Cyanobacterial and diatom samples collecteced between April and September 2022, and sequenced for metabarcodig of 16S and rbcL.

These data are the sample information for each of the samples collected for metabarcoding of 16S and rbcL to describe Cyanobacterial and diatom diversity, respectively, in three sites in Alpena, Michigan, one site in Monroe, Michigan, and one site in Palm Coast, Florida. Sample data are for sequenced samples and include their associated water parameter information that was collected simultaneously. Each of these sites are high-sulfur, low-oxygen environments formed by underwater sinkholes and springs that create extreme habitats populated by microbial mat communities. Our study investigated previously undescribed diatom diversity in these habitats, and further explored the bacterial communities as well. Our results provide novel information on microbial mat community composition, and present evidence that microbial biogeography influences these unique communities.