High reactivity of deep biota under anthropogenic CO2 injection into basalt

Rosalia Trias,Juerg M Matter,Sigurður R Gislason,Bénédicte Ménez,Sandra Ó Snæbjörnsdóttir,Jenny Uhl,Philippe Schmitt-Kopplin,Helgi A Alfreðsson,Eric H Oelkers,Ingvi Gunnarsson,Yvan Zivanovic,Edda S Aradóttir,Emmanuelle Gérard,Kiflom G Mesfin,Paul Le Campion,Aurélien Lecoeuvre,Léna Lecourt,Martin Stute

doi:10.1038/s41467-017-01288-8

Abstract

Basalts are recognized as one of the major habitats on Earth, harboring diverse and active microbial populations. Inconsistently, this living component is rarely considered in engineering operations carried out in these environments. This includes carbon capture and storage (CCS) technologies that seek to offset anthropogenic CO2 emissions into the atmosphere by burying this greenhouse gas in the subsurface. Here, we show that deep ecosystems respond quickly to field operations associated with CO2 injections based on a microbiological survey of a basaltic CCS site. Acidic CO2-charged groundwater results in a marked decrease (by ~ 2.5–4) in microbial richness despite observable blooms of lithoautotrophic iron-oxidizing Betaproteobacteria and degraders of aromatic compounds, which hence impact the aquifer redox state and the carbon fate. Host-basalt dissolution releases nutrients and energy sources, which sustain the growth of autotrophic and heterotrophic species whose activities may have consequences on mineral storage.

Highlights

Basalts are recognized as one of the major habitats on Earth, harboring diverse and active microbial populations
Our study focuses on the CO2-injection site associated with the Hellisheidi geothermal powerplant (SW-Iceland) and developed in the framework of the Carbfix project to assess the feasibility of carbon capture and in situ mineral storage in basalt[2,11]
From mid-January to August 2012, 175 t of commercial CO2 and 73 t of a gas mixture, derived from the purification of the geothermal gas harnessed by the plant (75% CO2-24.2% H2S-0.8% H2), were consecutively injected with reactive and non-reactive tracers (Supplementary Fig. 2; Supplementary Table 1)[12,13,14]

Summary

Introduction

Basalts are recognized as one of the major habitats on Earth, harboring diverse and active microbial populations. Little is known about the nature and metabolic diversity of microbial communities living in basalt-systems[9] or the biogeochemical reactions they can provoke following CO2 injection, including biologically-enhanced or -inhibited conversion of CO2 into solid carbonates[10] Their ability to impact the chemistry of their environment and subsequently affect the fate of injected CO2 makes deep-indigenous microbial populations potential critical factors for carbon immobilization. Phylogenetic diversity and abundance along with metabolic potential by bacterial 16S-rRNA gene 454-pyrosequencing, as well as archaeal and bacterial 16S-rRNA gene Sanger sequencing, quantitative polymerase chain reaction (qPCR), PCR detection of key genes for inorganic carbon assimilation and degradation of aromatic compounds and metagenomic analysis These approaches allow us to enumerate function and identity genes, and evidence changes compared to the native microbial community

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Results

Conclusion