Aquatic biofilms, also referred to as the "microbial skin" of aquatic ecosystems, play a key role in various ecosystem functions such as primary production or degradation of dissolved organic material and pollutants. They are situated in boundary layers such as the interstitium or the plastisphere and are therefore exposed to various stress factors. However, despite their important ecological role and recognized value for bioindication, their responses to multiple stressors are poorly understood. In this presentation recent findings of biofilm community responses to single and combined stressors at different biological scales will be presented. Stress responses manifest at levels of regulation, acclimation and adaptation/microevolution. Unraveling these processes requires approaches from the molecular/biochemical to structural and functional level. Recent biofilm studies on stress responses across scales, as well as the challenge of how to compare these responses will be discussed. A key concept for understanding interactions between multiple stressor effects, the concept of stress-induced community tolerance, will be illustrated.  The studies will be framed within the concept of co-tolerance to understand resilience mechanisms to combined stressors and outline the consequences of induced tolerance and the associated fitness costs for ecosystem functions.

Primary Presenter: Mechthild Schmitt-Jansen, Helmholtz Centre for Environmental Research - UFZ (mechthild.schmitt@ufz.de)

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