Groundwater ecosystems and their services: current status and potential risks

Earth’s ecosystems provide a multitude of goods and functions, recently conceptualized under the term ecosystem services (ES; [1]). Many of these services and their associated ecosystems have received considerable attention, but groundwater ecosystems, soils, and sediments that are hidden below our feet are often overlooked. In fact, subsurface ecosystems deliver services of immense societal and economic value, most prominently the purification of water through (1) nutrient cycling; (2) biodegradation of contaminants; (3) inactivation and elimination of pathogens; and (4) storage and transmission of water that can mitigate floods and provide a stable water supply during droughts. Several of these services are directly connected to the presence and activity of the microorganisms and metazoans living in groundwater. We argue that, due to global and climate change, many of the groundwater ecosystem services are at serious risk. The pressures on groundwater ecosystems include aspects of global change such as local (point) and diffuse (non-point) sources of contamination, and overexploitation of groundwater resources. Moreover, even though groundwater ecosystems are located below ground, their organisms and the services they provide are affected by climate change—inter alia through changes in temperature regime as well as changes in recharge patterns and hydrological conditions due to floods and droughts