The Contribution of Water Radiolysis to Marine Sedimentary Life

Justine Sauvage

Department of Marine Sciences
University of Gothenburg

Friday, Oct. 30, 2020, 3:10pm

Water radiolysis continuously produces H2 and oxidized chemicals in wet sediment and rock. Radiolytic H2 has been identified as the primary electron donor (food) for microorganisms in continental aquifers kilometers below Earth’s surface. Radiolytic products may also be significant for sustaining life in subseafloor sediment and subsurface environments of other planets. However, the extent to which most subsurface ecosystems rely on radiolytic products has been poorly constrained, due to incomplete understanding of radiolytic chemical yields in natural environments. Our experiments show that all common marine sediment types catalyze radiolytic H2 production, amplifying yields by up to 27X relative to pure water. In electron equivalents, the global rate of radiolytic H2 production in marine sediment appears to be 1-2% of the global organic flux to the seafloor. However, most organic matter is consumed at or near the seafloor, whereas radiolytic H2 is produced at all sediment depths. Comparison of radiolytic H2 consumption rates to organic oxidation rates suggests that water radiolysis is the principal source of biologically accessible energy for microbial communities in marine sediment older than a few million years. Where water permeates similarly catalytic material on other worlds, life may also be sustained by water radiolysis.


Justine Sauvage received her PhD in Oceanography at the Graduate School of Oceanography, University of Rhode Island, under the guidance of Prof. Steven D’Hondt. Sauvage sailed as an inorganic geochemist on two IODP expeditions focused on unravelling Earth’s subseafloor microbial world, its extent, diversity, and metabolic landscape. After her PhD, Sauvage started a post doc at the Department of Marine Sciences, University of Gothenburg, Sweden, where she applies her background in oceanography, biogeochemistry and ecology for development of integrated and sustainable solutions for the management of marine resources. Current projects include (i) optimization of microalgae cultivation systems as key component of a sustainable ‘circular’ aquaculture industry, (ii), development of functional aquafeeds, and (iii) implementation of aquaculture components within integrated food production systems (e.g. biofloc technology and aquaponics).