Riverbed sediment microbiome

Microorganisms in aquatic sediments are key drivers of ecosystem processes in freshwaters. Any anthropogenic pressure and/or stressor in the catchment or within the water body directly or indirectly affects microbial community structure (i.e., community composition, biomass, etc.) and function (i.e., microbial respiration, exo-enzyme activities, etc.). Fast development of molecular and ecophysiological techniques, producing vast amount of high quality biological information, offers an opportunity for development of new biological indicators providing sound information on specific stressors. In this study, a preliminary investigation of both structural (i.e., microbial biomass and community composition) and functional (i.e., respiratory potential, measured as electron transport system activity (ETSA) and community-level physiological profiling (CLPP)) response to pollution gradient was carried out in a pre-alpine gravel bed river in Slovenia (SE Europe). The 16S rRNA gene analyses, ETSA and CLPP revealed to be informative structural and functional indicators for detecting discharge of WWTP effluents to the river and agricultural activity in the catchment. The investigation of linkages between community composition and ecophysiological activity demonstrated strong correlation. Further studies should be implied to find indicative OUTs and indicative metabolic profiles providing specific information on the stressors affecting ecological processes in freshwater bodies.