CONICET | Buscador de Institutos y Recursos Humanos

The aim of this study was to describe the colonization of the biofilm during its early stages under different concentrations of nutrients and organic matter, specifically in urban streams influenced by agriculture and urbanization. We hypothesized that in a stream with higher concentrations of nutrients and organic matter, the initial biomass growth would be faster, and the changes in the structure of the community would be greater. Sterile glass substrates were placed in 2 urban streams that differed in nutrient and organic matter concentrations; samples were collected during their first week of colonization to measure total biomass, bacterial biomass, chlorophyll a, activity of the electron transfer system, and the community composition. Results show that biofilm development in both streams began within a few hours and differed under different conditions of nutrients; in the stream with a better water quality, the colonization dynamics consisted of 2 increments of bacterial biomass linked with an increase of algal biomass. In the urban stream with higher nutrient and organic matter concentrations, biofilm development was slower and consisted of a simultaneous increase of bacteria and algae, consistent with a lower electron transfer system activity. Therefore, the dynamics of the colonization process in addition to those characteristics of the fully developed biofilm could have potential applications in water monitoring of urban streams.