Shallow geothermal energy usage and its potential impacts on groundwater ecosystems

The use of shallow geothermal energy is a thriving technology. Still, its impact on the ecology of subsurface habitats has not been adequately investigated. Biological processes are substantially influenced by temperature. In field and laboratory investigations comprising a temperature range from 2 to 45 degrees C we show, that the diversity and structure of aquifer microbial communities is significantly influenced by temperature. Microbial biomass and activities are shown to additionally depend on the availability of nutrients and substrates in the groundwater. Selected groundwater invertebrates exhibited little tolerance towards mid-and long-term exposure to increased temperatures. Our results allow first recommendations towards the design, authorization, construction and operation of shallow geothermal energy facilities in an ecologically sustainable way.