ISATAB-MBL-6
Eukaryotic diversity at pH extremes
Extremely acidic (pH<3) and extremely alkaline (pH>9) environments support a diversity of both single-cell and multicellular eukaryotic life. This study compared eukaryotic communities from 7 diverse aquatic environments with pH values ranging from 2 to 11 including: an acid rock drainage stream in the Rio Tinto, Spain; an acid mine drainage stream in Davis Mine, Massachusetts; the thermal-acidic Nymph Creek in Yellowstone National Park (YNP), Wyoming; two alkaline Sandhills lakes in Nebraska; alkaline hypersaline Mono Lake in California; and the alkaline hydrothermal fields of Lost City, using massively-parallel pyrotag sequencing targeting the V9 hypervariable region of the 18S ribosomal RNA (rRNA) gene. A total of 946 Operational Taxonomic Units (OTUs) were recovered at a 6% cut-off level (94% similarity) across the sampled environments. Indicator Species Analysis (ISA) and Non-metric Multidimensional Scaling (NMDS) were used to determine whether characteristic groups of eukaryotic taxa typify pH extremes and the extent to which pH shapes eukaryotic community structure in these environments. The Rio Tinto yielded the fewest observed OTUs while Sandhills alkaline lakes yielded the greatest. Distinct OTUs, including metazoa, numerically dominated different pH extreme sites. Indicator OTUs included diatom and fungal OTUs in the extremely acidic environments, and the ciliate Frontonia across the extremely alkaline sites. pH explained only a modest fraction of the variation across the datasets. Environmental factors in addition to pH likely influence the underlying community structure in these environments. Only 2 OTUs were shared across all 7 sites a diatom belonging to the Fragilariophyceae and an arthropod with 100% identity to an environmental clone. This suggests that ability for eukaryotes to adapt to pH extremes over a broad range of values is quite rare, and these exceptions may provide good models for understanding adaptation across pH extremes. Deposition to NCBI SRA via ISAcreator 1.6 tool (www.isatab.sf.net), compliant with MIMARKS requirements