Aquatic ecosystems are threatened by acid precipitation from atmospheric depositions of sulphur dioxide and nitrogen oxides emitted from automobiles and industries. The ability of the acidophilic diatom genus Eunotia Ehrenberg to respond to and distinguish between interactions between varied geology and anthropogenic pressures on natural environments make these algae good potential indicators of acid pollution. We examined the ecology and distribution patterns of Eunotia collected from bryophytes at springs and streams throughout the Great Smoky Mountains National Park which has a range of acidic, aquatic  habitats amongst a complex geology at a variety of altitudes. Relative abundance and community composition were examined in relation to water chemistry (such as nitrates and metals), pH, and altitude. High elevation spring areas were dominated by E. subarcuatoides, several of which showed morphological deformities. The southwestern areas of the park were comprised of taxa such as E. formica , which reflected the circumneutral pH levels. This contrasted with the more acidic and higher elevation streams which were dominated by taxa from the E. exigua complex. The ecological ranges and species complexes identified in this study will help to refine and expand the indicator potential of taxa in this genus.