Sammendrag
Determining whether the structural and functional stress responses of communities are similar across
space and time is paramount for forecasting and extrapolating the consequences of anthropogenic
pressures on ecosystems and their services. Stream ecosystems are under high anthropogenic pressure;
however, studies have only examined the response of stream communities across large scales over
multiple generations. We studied the responses of leaf-associated microbial communities in streams
within three European biogeographical regions to chemical stress in a microcosm experiment with
multiple cycles of fungicide pollution and resource colonisation. Fungal community composition
and the ecosystem function leaf decomposition were measured as response variables. Microbial leaf
decomposition showed similar recovery times under environmental levels of fungicide exposure
across regions. Initially, the decomposition declined (between 19 and 53%) under fungicide stress and
recovered to control levels during the third cycle of pollution and colonisation. Although community
composition and its stress response varied between regions, this suggests similar functional community
adaptation towards fungicide stress over time. Genetic, epigenetic and physiological adaptations,
as well as species turnover, may have contributed to community adaptation but further studies are
required to determine if and to which extent these mechanisms are operating. Overall, our fndings
provide the frst evidence of a similar functional response of microbial leaf decomposition to chemical
stress across space and time.
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