A meta-taxonomic investigation of the prokaryotic diversity of water bodies impacted by acid mine drainage from the São Domingos mine in southern Portugal.

The prokaryotic communities of water bodies contaminated by acid mine drainage from the São Domingos mining area in southern Portugal were analyzed using a meta-taxonomics approach with 16S rRNA gene sequences. Samples were collected in two seasonal sampling campaigns (summer and winter of 2017) from the most contaminated sites from where the water flows downstream to the freshwater reservoir of the river Chança. The physicochemical data indicate a trend of decreasing acid mine drainage contamination downstream of the mining area to the Chança's reservoir. The most contaminated sites (pH = 2.3-3.1) are distinguished by prokaryotic diversity with high abundances of operational taxonomics units related to acidophiles (genera Metallibacterium, Acidibacter, Leptospirillum, Acidobacterium, Thiomonas, Acidicapsa, Acidocella, Acidiphilium; family Acidobacteriaceae, order CPla-3 termite group). Likewise, in the transition zone in the mouth of the contaminated water flow into the Chança´s reservoir (pH = 6.4), a specific prokaryotic flora exists with some acidophiles, but notably with a cyanobacteria bloom and a high abundance of the genus Sediminibacterium (family I; order Subsection III). Moreover, the strong correlation between the abundance of acidophiles and characteristic physiochemical parameters (metals, acidity, and sulfate) confirm their potential as biomarkers of acid mine drainage pollution.