The use of epilithic biofilms as bioaccumulators of pesticides and pharmaceuticals in aquatic environments

Biofilms are a consortium of communities of organisms that live in syntrophic relationships and present a higher organization level than that of individual cells. Biofilms dominate microbial life in streams and rivers, enable crucial ecosystem processes, contribute to global biogeochemical flows and represent the main active bacterial life form. Epilithic biofilms are the main biomass found in rivers; their exposure to contaminants can lead to changes in their structure and composition. The composition of these communities is influenced by physicochemical factors, temperature, light and prior exposure to pollutants, among other factors, and it can be used for water quality monitoring purposes. The heterogenous composition of biofilms enables them to accumulate compounds in an integrative manner. Moreover, the availability of several sorption sites and their likely saturation can contribute to bioaccumulation. In aquatic environments, biofilms are also susceptible to the acquisition of antibiotic resistance genes and participate in their dissemination. Anthropic pressure intensification processes continuously expose water resources and, consequently, biofilm communities to different contamination sources. Therefore, the use of biofilms to indicate environmental pollution is reinforced by the progress of studies on the subject. Biofilm communities' response to pollutants in aquatic environments can be mainly influenced by the presence of different organisms, which may change due to community development or age. The current research aims to review studies about biofilm contamination and highlight the importance of biofilm use to better evaluate and maintain the quality of water bodies.