Candidatus Desulforudis audaxviator dominates a 975 m deep groundwater community in central Sweden.

The continental bedrock contains groundwater-bearing fractures that are home to microbial populations that are vital in mediating the Earth's biogeochemical cycles. However, their diversity is poorly understood due to the difficulty of obtaining samples from this environment. Here, a groundwater-bearing fracture at 975 m depth was isolated by employing packers in order to characterize the microbial community via metagenomes combined with prokaryotic and eukaryotic marker genes (16S and 18S ribosomal RNA gene).

Microscale δS and δO variations of barite as an archive for fluid mixing and microbial sulphur metabolisms in igneous rock aquifers.

The stable isotope compositions of sulphur (δS) and oxygen (δO) in barite are frequently used as proxies for microbial sulphate reduction (MSR) in diverse environments, such as in relation to anaerobic oxidation of methane in marine cold seeps. There, isotopically heavy barite is used as a marker for MSR from a sulphate pool that has undergone semi-closed system conditions. Closed-system MSR is also a commonly observed feature in igneous rock hosted fracture aquifers, as shown by extremely S-enriched pyrite.

Observations of diapycnal upwelling within a sloping submarine canyon.

Small-scale turbulent mixing drives the upwelling of deep water masses in the abyssal ocean as part of the global overturning circulation. However, the processes leading to mixing and the pathways through which this upwelling occurs remain insufficiently understood. Recent observational and theoretical work has suggested that deep-water upwelling may occur along the ocean's sloping seafloor; however, evidence has, so far, been indirect.