Metals alter membership but not diversity of a headwater stream microbiome
Metal contamination from mining or natural weathering is a common feature of surface waters in the American west. Traditionally, stream macroinvertebrate community metrics have been used for stream quality assessments. Advances in microbial analyses have created the potential for routine sampling of aquatic microbiomes as a tool to assess the quality of stream habitat. We sought to determine if microbiome diversity and membership were affected by metal contamination in a manner similar to what
... er similar to what has been observed for stream macroinvertebrates, and if so, identify candidate microbial taxa to be used to indicate metal stress in stream ecosystems. We evaluated microbiome membership from sediments at multiple sites within the principal drainage of an EPA superfund site near the headwaters of the Upper Arkansas River, Leadville, CO. From each sample, we extracted DNA and sequenced the 16S rRNA gene amplicon on the Illumina MiSeq platform. We used the remaining sediments to simultaneously evaluate environmental metal concentrations. We also conducted an artificial stream mesocosm experiment using sediments collected from two of the observational study sites. The mesocosm experiment had a 2x2 factorial design: 1) location (upstream or downstream of contaminating tributary), and 2) treatment (metal exposure or control). We found no difference in diversity between upstream and downstream sites in the field. Similarly, diversity changed very little following experimental metal exposure. However, microbiome membership differed between upstream and downstream locations and experimental metal exposure changed microbiome membership in a manner that depended on origin of the sediments used in each mesocosm.