Biofilms as integrative indicators of global change in freshwaters

Addressing the growing impacts of global change on freshwater ecosystems requires the provision of reliable diagnostic tools capable of detecting, integrating, and diagnosing multiple environmental stressors. Due to their functional versatility and rapid responses, biofilms emerge as valuable indicators of stressors presently affecting freshwater systems. A range of tools is presently available to assess biofilm dynamics across spatial and temporal scales, though their effectiveness is limited by the intrinsic complexity of biofilm communities and the interplay of stressors. To improve their utility, it is essential to adequately integrate the structural and functional information they provide. We here synthesize the current knowledge on how freshwater biofilms perform as indicators of global change, particularly regarding stressors associated to physical impacts and pollution. Evidence highlights both their underexplored potential and inherent limitations within ecological monitoring frameworks. Among these, it may be stressed the insufficient integration of the available information, the lack of integrative tools, and the insufficient standardization. We propose a roadmap to apply biofilm indicators to specific stressors and adapting consistent response patterns to co-occurring stressors.