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Abstract
High altitude springs and headwater streams directly interact with atmospheric deposition and as a result may be useful first response bioindicators of changes in acid precipitation, i.e. from increased acid rain or mitigation efforts. We examined the diatom assemblages associated with bryophytes collected from high elevation springs and streams in the Great Smoky Mountains National Park, U.S.A. in 2005 and 2007. The high elevation areas were dominated by Eunotia taxa, primarily E. subarcuatoides Alles, Nörpel et Lange-Bert., and secondarily by E. exigua (Bréb. ex Kütz.) Rabh., E. muscicola var. tridentula Nörpel et Lange-Bert., and E. macroglossa sp. nov.
The presence of valve malformations in four of the high elevation springs and two streams suggest that acid precipitation in the park may be interacting with local bedrock geology to release metals toxic to algal communities, especially under the low pH conditions of these high elevation areas. Sites with the greatest number of deformities showed higher levels of Al, Ba, and Mn relative to other sites. Internal and external diatom morphology of normal and abnormal E. subarcuatoides valves were explored and demonstrated the presence of valve aberrations across all size ranges, including shape distortions and unusual raphe development. No difference in mean valve length or size range was present between normal and abnormal valves. However, more data are necessary before any clear linkages between diatom deformities, metals, geology, and acid precipitation can be unequivocally established.