MICROBIAL COMMUNITY RESPONSE TO WATER STRESS IN A TEMPORARY RIVER ECOSYSTEM

Temporary waters are widespread in the Mediterranean area as well as in many other world wide semiarid regions. Global climate changes could prolong dry periods and influence the dynamic of biological processes in sediments. Bacteria play a key role in river-bed ecosystem processes as mediators of organic matter decomposition and nutrient cycling. Water availability affects the osmotic status of bacterial cells inducing a selective pressure on the structure and functioning of sediment communities. In spite of the importance in nutrient cycling there is a lack of understanding on how the activities of bacterial communities in sediments respond to drying and rewetting cycles. The Mulargia stream, a tributary of the Flumendosa-Campidano hydraulic system, is characterized by extended dry periods in summer and intense flush events in early autumn. This study aims to monitor changes of microbial communities as function of water stress in the Mulargia sediment. We will present data on bacterial abundance, live/dead ratio, C incorporation and enzymatic activities rates and phylogenetic diversity. Results indicate the effect of water stress on the physiological status of the bacterial community and a wide variability along the stream, depending on nutrient enrichment.