Sulfur bacteria promote dissolution of authigenic carbonates at marine methane seeps.

Affiliation

Leprich DJ(1), Flood BE(2), Schroedl PR(2), Ricci E(2), Marlow JJ(3), Girguis PR(4), Bailey JV(5).
Author information:
(1)Department of Earth and Environmental Sciences, University of Minnesota Twin-Cities, Minneapolis, MN, 55455, USA. [Email]
(2)Department of Earth and Environmental Sciences, University of Minnesota Twin-Cities, Minneapolis, MN, 55455, USA.
(3)Department of Biology, Boston University, Boston, MA, 02215, USA.
(4)Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
(5)Department of Earth and Environmental Sciences, University of Minnesota Twin-Cities, Minneapolis, MN, 55455, USA. [Email]

Abstract

Carbonate rocks at marine methane seeps are commonly colonized by sulfur-oxidizing bacteria that co-occur with etch pits that suggest active dissolution. We show that sulfur-oxidizing bacteria are abundant on the surface of an exemplar seep carbonate collected from Del Mar East Methane Seep Field, USA. We then used bioreactors containing aragonite mineral coupons that simulate certain seep conditions to investigate plausible in situ rates of carbonate dissolution associated with sulfur-oxidizing bacteria. Bioreactors inoculated with a sulfur-oxidizing bacterial strain, Celeribacter baekdonensis LH4, growing on aragonite coupons induced dissolution rates in sulfidic, heterotrophic, and abiotic conditions of 1773.97 (±324.35), 152.81 (±123.27), and 272.99 (±249.96) μmol CaCO3 • cm-2 • yr-1, respectively. Steep gradients in pH were also measured within carbonate-attached biofilms using pH-sensitive fluorophores. Together, these results show that the production of acidic microenvironments in biofilms of sulfur-oxidizing bacteria are capable of dissolving carbonate rocks, even under well-buffered marine conditions. Our results support the hypothesis that authigenic carbonate rock dissolution driven by lithotrophic sulfur-oxidation constitutes a previously unknown carbon flux from the rock reservoir to the ocean and atmosphere.