Mixing of meteoric and geothermal fluids supports hyperdiverse chemosynthetic hydrothermal communities

Daniel R Colman,Melody R Lindsay,Eric S Boyd

doi:10.1038/s41467-019-08499-1

Daniel R Colman, Melody R Lindsay + Show 1 more

Open Access

https://doi.org/10.1038/s41467-019-08499-1

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Abstract

Little is known of how mixing of meteoric and geothermal fluids supports biodiversity in non-photosynthetic ecosystems. Here, we use metagenomic sequencing to investigate a chemosynthetic microbial community in a hot spring (SJ3) of Yellowstone National Park that exhibits geochemistry consistent with mixing of a reduced volcanic gas-influenced end member with an oxidized near-surface meteoric end member. SJ3 hosts an exceptionally diverse community with representatives from ~50% of known higher-order archaeal and bacterial lineages, including several divergent deep-branching lineages. A comparison of functional potential with other available chemosynthetic community metagenomes reveals similarly high diversity and functional potentials (i.e., incorporation of electron donors supplied by volcanic gases) in springs sourced by mixed fluids. Further, numerous closely related SJ3 populations harbor differentiated metabolisms that may function to minimize niche overlap, further increasing endemic diversity. We suggest that dynamic mixing of waters generated by subsurface and near-surface geological processes may play a key role in the generation and maintenance of chemosynthetic biodiversity in hydrothermal and other similar environments.

Highlights

Little is known of how mixing of meteoric and geothermal fluids supports biodiversity in nonphotosynthetic ecosystems
The Smokejumper geyser basin (SJGB) is located at high elevation, and near the continental hydrological divide of the Americas and on the edge of the Yellowstone caldera boundary (Fig. 1), where extensivefaulting and fracturing of volcanic bedrock is thought to promote the release of gases that were exsolved during subsurface phase separation[27]
Phase separated volcanic gas-influenced geothermal fluids are often enriched in H2, CO, and short-chain alkanes due to interaction between geothermal fluids and ferrous iron containing minerals in bedrock during ascension of the gases and waters to the surface[24]

Summary

Introduction

Little is known of how mixing of meteoric and geothermal fluids supports biodiversity in nonphotosynthetic ecosystems. Numerous studies have documented the presence of microbial communities in subsurface environments[1,5,6,7]; little is known of how the confluence of subsurface and surfaceassociated processes promotes the generation and maintenance of biodiversity in subsurface, chemosynthetic systems. This is due largely to difficulties in accessing these ecosystems and isolating fluid types that source these environments. These discrepancies suggest geochemical controls on the generation and maintenance of chemosynthetic hot spring community biodiversity

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