Overview of sample details including site characteristics, pyrotag analysis, and cell counts.

Site abbreviations; RB, Rainbow; TAG, Trans-Atlantic Geotraverse; SP, Snake Pit. Dist, distance (in meters) to closest sulfide chimney. Tmax, maximum temperature of diffuse flow associated with sample. mbsl, meters below sea level. Cell count reported as mean (SD). Nseqs, total number of pyrotag reads. Sobs, total number of OTUs. *Alpha-diversity estimates based on sub-sampled pyrotag reads. 1/D, Inverse Simpson Index; Q, Q-statistic; d, Berger-Parker Index; C, Good’s Coverage. Overview of sample details including site characteristics, pyrotag analysis, and cell counts.