Spatio-temporal patterns of suspended and attached bacterial communities in a hydrologically dynamic aquifer (Mittenwald, Germany).

Groundwater ecosystems are perceived as energy-poor systems very stable in environmental conditions and consequently harboring stable microbial communities of low diversity. In a hydrologically transient porous aquifer (Mittenwald, Germany), pronounced seasonal patterns of bacterial communities suspended in groundwater, exhibiting a dramatic drop in Shannon diversity at time of snow melting water impact, were found while the attached communities were found comparably stable year-round. The succession of dominant taxa within the bacteria during colonization of sterile sediments exposed to groundwater in situ indicated the presence of r- and K-strategists within the bacteria. A first estimation of carbon flux through the suspended microbial food web hinted at bacterial mortality induced by protozoan grazing and viral lysis