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Light availability affects stream biofilm bacterial community composition and function, but not diversity
Author(s) -
Wagner Karoline,
Besemer Katharina,
Burns Nancy R.,
Battin Tom J.,
Bengtsson Mia M.
Publication year - 2015
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12913
Subject(s) - biofilm , biology , biogeochemical cycle , organic matter , microcosm , phototroph , dissolved organic carbon , heterotroph , nutrient cycle , ecosystem , environmental chemistry , ecology , temperature gradient gel electrophoresis , microbial population biology , aquatic ecosystem , botany , photosynthesis , bacteria , chemistry , genetics , 16s ribosomal rna
Summary 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.