Terrigenous dissolved organic matter persists in the energy-limited deep groundwaters of the Fennoscandian Shield

Congratulations to AMRI Co-PI Mark Dopson and co-authors on their publishing of Terrigenous dissolved organic matter persists in the energy-limited deep groundwaters of the Fennoscandian Shield in Nature Communications! Stay tuned for an AMRI interview with Mark about the fascinating research that went into this paper in our next Roundup.

Osterholz, H., Turner, S., Alakangas, L.J. et al. Terrigenous dissolved organic matter persists in the energy-limited deep groundwaters of the Fennoscandian Shield. Nat Commun 13, 4837 (2022). https://doi.org/10.1038/s41467-022-32457-z

Margarita Lopez-Fernandez

Abstract:

The deep terrestrial biosphere encompasses the life below the photosynthesis-fueled surface that perseveres in typically nutrient and energy depleted anoxic groundwaters. The composition and cycling of this vast dissolved organic matter (DOM) reservoir relevant to the global carbon cycle remains to be deciphered. Here we show that recent Baltic Sea-influenced to ancient pre-Holocene saline Fennoscandian Shield deep bedrock fracture waters carried DOM with a strong terrigenous signature and varying contributions from abiotic and biotic processes. Removal of easily degraded carbon at the surface-to-groundwater transition and corresponding microbial community assembly processes likely resulted in the highly similar DOM signatures across the notably different water types that selected for a core microbiome. In combination with the aliphatic character, depleted δ13C signatures in DOM indicated recent microbial production in the oldest, saline groundwater. Our study revealed the persistence of terrestrially-sourced carbon in severely energy limited deep continental groundwaters supporting deep microbial life.