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Changes in riparian vegetation or water turbidity and browning in streams alter the local light regime with potential implications for stream biofilms and ecosystem functioning. We experimented with biofilms in microcosms grown under a gradient of light intensities (range: 5-152 μmole photons s-1 m-2 ) and combined 454-pyrosequencing and enzymatic activity assays to evaluate the effects of light on biofilm structure and function. We observed a shift in bacterial community composition along the light gradient, whereas there was no apparent change in alpha diversity. Multifunctionality, based on extracellular enzymes, was highest under high light conditions and decoupled from bacterial diversity. Phenol oxidase activity, involved in the degradation of polyphenolic compounds, was twice as high on average under the lowest compared with the highest light condition. This suggests a shift in reliance of microbial heterotrophs on biofilm phototroph-derived organic matter under high light availability to more complex organic matter under low light. Furthermore, extracellular enzyme activities correlated with nutrient cycling and community respiration, supporting the link between biofilm structure-function and biogeochemical fluxes in streams. Our findings demonstrate that changes in light availability are likely to have significant impacts on biofilm structure and function, potentially affecting stream ecosystem processes.
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Tom Ian Battin, Susheel Bhanu Busi, Vincent Henri De Staercke, Stylianos Fodelianakis, Tyler Joe Kohler, Hannes Markus Peter, Paraskevi Pramateftaki, Martina Andrea Schön, Michail Styllas, Matteo Tolosano
Tom Ian Battin, Massimo Bourquin, Jade Brandani, Susheel Bhanu Busi, Vincent Henri De Staercke, Nicola Deluigi, Leïla Ezzat, Stylianos Fodelianakis, Tyler Joe Kohler, Grégoire Marie Octave Edouard Michoud, Hannes Markus Peter, Paraskevi Pramateftaki, Martina Andrea Schön, Michail Styllas, Matteo Tolosano
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