Fig. 1: Overview of sampling area and impressions of Auka vent field.

A Bathymetric map of Auka vent field with the most prominent sites of focused hydrothermal venting labeled by name. The sampling locations of push cores analyzed in this study are indicated, with the cores used for metagenomic sequencing highlighted in orange. DR750 is the dive number from cruise MBARI2015. S0193, S0194, S0196, S0198, and S0200 are dive numbers from cruise FK181031. Samples collected during cruise NA091 are indicated with cruise sample number B Diane’s vent, a chimney with distinctive clear hydrothermal fluid discharge clearly visible. C Top of the Matterhorn, a ~10 m high free-standing chimney, with the area around the central orifice fully covered in Oasisia sp. tubeworms. Microbial mat and shallow flange structures are visible on the sides of the chimney, indicative of diffuse fluid discharge through the chimney wall. D Carbonate platform covered in white and gray microbial mat with Oasisia sp. tubeworms (~20 cm tall) clustered around a localized spot of hydrothermal fluid discharge. This is a representative example of the unlabeled elevated mounds shown in A. E Sediment covered in microbial mat (at Diane’s vent) with heterogeneity of colors and textures indicating centimeter scale spatial heterogeneity in fluid diffusion through the sediment. Push core locations in A correspond to areas with prevalent microbial mats.