Microorganisms in aquifers deep below the earth’s surface produce similar amounts of biomass as those in some marine waters.
Microorganisms in aquifers deep below the earth’s surface produce similar amounts of biomass as those in some marine waters. This is the finding of researchers led by the Friedrich Schiller University Jena and the German Centre for Integrative Biodiversity Research (iDiv). Applying a unique, ultra-sensitive measurement method using radioactive carbon, they were able to demonstrate for the first time that these biotic communities in absolute darkness do not depend on sunlight. Instead, they can obtain energy autonomously from rock oxidation or from compounds transported into the deep. The study has been published in Nature Geoscience.
Terrestrial and marine habitats have been considered the ecosystems with the highest primary production on earth by far, i.e., the conversion of inorganic to organic carbon. Microscopic algae in the upper layers of the oceans and plants on land bind atmospheric carbon (CO2) and produce plant material driven by photosynthesis, i.e. the sun provides energy. Since sunlight does not penetrate into the subsurface, hardly any such primary production is to be expected. So much for the theory.
However, genetic analyses of microorganisms in groundwater have indicated that even here many microorganisms are capable of primary production. In the absence of light, they must obtain the energy from oxidising inorganic compounds, like from reduced sulfur of the surrounding rocks. However, the role of primary producers in the subsurface had never been confirmed before.
Groundwater is one of our most important sources of clean drinking water. The groundwater environment of the carbonate aquifers alone, which is the focus of the study, provides about ten per cent of the world’s drinking water. With this in mind, the researchers carried out measurements of microbial microorganism carbon fixation in a subsurface aquifer, 5 to 90 metres below-ground.