A METHOD BASED ON ARTIFICIAL SUBSTRATES TO MONITOR HYPORHEIC BIOFILM DEVELOPMENT

A method based on artificial substrata is proposed to study hyporheic biofilm development as well as the procedure to remove bacteria from t hese biofilms. The device is a perforated pipe in which glass slides a re introduced vertically. Attached bacteria are removed by sonication for 180 seconds at power 2 (arbitrary unit); longer sonication time or higher power can cause cell destruction. A bacterial colonization exp eriment was performed in an upwelling zone of a riffle in the Rhone Ri ver. Total bacterial abundances reached a steady-state after 5 days of colonization, and the percentage of ETS-active bacteria was maximal a fter 3 days of incubation in the bed sediments. These results validate this device as usable to monitor biofilm development in natural syste ms, making this method as a promising tool to characterize the trophic status of a stream using integrative biological descriptors.