| Summary: | Microorganisms are dominant life forms on Earth, and they have a great impact on Earth's geobiological cycles and climate change. In addition to carbon and elemental cycling on the surface of earth it is now known that microorganisms can also reach several kilometres deep into earth crust. What are these microbes doing? And how deep they can survive? What energy they need? How to sample and study? What is their biodiversity- e.g. what species are there? What is the limit of life? What kind of metabolism deep subsurface geomicrobes have? Where we can utilize this knowledge ? Intensive studies has been ongoing since two decades to solve these questions. Most of the studies are due to International Ocean Drilling programs (http://www.iodp.org/) and Continental scientific drilling program (http://www.icdp-online.org). Our studies on deep biosphere of Fennoscandian Shield started already in 2006 in the Deep life project of Outokumpu deep drillhole (2.5km deep) . Deep sampling methods for microbiology were developed as well as methods to study biodiversity based on highthroughput sequencing. Since then 19 drillholes (300m-1000m ) in Olkiluoto the final disposal site for high radioactive waste has been studied, the deep mine Pyhäsalmi mine (2km) and some other smaller sites. The studies have revealed that biodiversity vary locally and is clearly connected to geology, geochemistry and gases evolving from the mantle or crust. The microbial cell counts decrease downwards being at near the surface ca 10.000 cells/ml and only 1000 cells at 2km depth. Iron and sulphur oxidizers and reducers are abundantly present in all samples. These microorganisms can oxidize and dissolve minerals from rock and use it as energy by reducing sulphate to sulphides. Other sources for energy evolving from crust is hydrogen which is formed abiotically in crust in iron water interactions and feed up deep subsurface microorganisms. In addition other minerals in rock can serve as energy for geomicrobes. Methane which has been detected in abundances ...
|
|---|