The seasonal population fluctuation of anoxygenic phototrophs and the diversity of cyanobacteria at the Sulphur Mountain thermal springs of Banff, Canada were investigated and compared to the drastic population changes of the endangered snail Physella johnsoni. A new species and two strains of Rhodomicrobium were taxonomically characterized in addition to new species of Rhodobacter and Erythromicrobium. Major mat-forming organisms included Thiothrix-like species, oxygenic phototrophs of genera Spirulina, Oscillatoria, and Phormidium and purple nonsulfur bacteria Rhodobacter, Rhodopseudomonas and Rhodomicrobium. Aerobic anoxygenic phototrophs comprised upwards of 9.6 x 104 CFU/cm2 of mat or 18.9% of total aerobic heterotrophic bacterial isolates at certain sites, while maximal purple nonsulfur and purple sulfur bacteria were quantified at 3.2 x 105 and 2.0 x 106 CFU/cm2 of mat, respectively. Photosynthetic activity measurements revealed incredibly productive carbon fixation rates averaging 40.5 mg C/cm2/24 h. A temporal mismatch was observed for mat area and prokaryote-based organics to P. johnsoni population flux in a “tracking inertia” manner.