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TitleSediment microbial communities rely on different dissolved organic matter sources along a Mediterranean river continuum
AbstractHeterotrophic bacteria play a key role in the degradation of organic matter and carbon cycling in river sediments. These bacterial communities are directly influenced by environmental variables that differ spatially and temporally in rivers. Here, we studied the longitudinal patterns of sediment bacterial community composition and dissolved organic matter utilization under base flow and drought conditions in a Mediterranean river. Our results indicated that sediment microbial communities were affected by dissolved organic matter quality and origin along the river continuum. In headwaters the potential degradation of cellulose and hemicellulose was greater (i.e., higher beta-glucosidase and beta-xylosidase activities), suggesting higher microbial utilization of allochthonous detritus from terrestrial origin. Conversely, the accumulation and transport of more recalcitrant compounds (i.e., decrease in the recalcitrant index) became potentially relevant downstream. Furthermore, discharge fluctuations had clear effects on bacterial community composition and dissolved organic matter use. The hydrological fragmentation of the river continuum during drought period generated sediment microhabitats dominated by gamma and delta-Proteobacteria, with a greater potential capacity to degrade a wide range of compounds, particularly nitrogen containing moieties. During base flow conditions, we observed a higher occurrence of alpha-Proteobacteria and a greater potential use of more recalcitrant carbon compounds, mostly of terrestrial origin. Overall, our findings suggest an upstream-downstream longitudinal transition of sediment microbial communities that rely on allochthonous to autochthonous dissolved organic matter, and a shift toward autochthonous dissolved organic matter reliance during drought.
SourceLimnology and oceanography 61 (4), pp. 1389–1405
KeywordsbacteraMediterranean rivers
JournalLimnology and oceanography
EditorAmerican Society of Limnology and Oceanography., [Waco, Tex., etc.], Stati Uniti d'America
Year2016
TypeArticolo in rivista
DOI10.1002/lno.10308
AuthorsFreixa, A.; Ejarque, E.; Crognale, S.; Amalfitano, S.; Fazi, S.; Butturini, A.; Romani, A. M.
Text372302 2016 10.1002/lno.10308 ISI Web of Science WOS 000383622900018 Scopus 2 s2.0 84971426956 bactera Mediterranean rivers Sediment microbial communities rely on different dissolved organic matter sources along a Mediterranean river continuum Freixa, A.; Ejarque, E.; Crognale, S.; Amalfitano, S.; Fazi, S.; Butturini, A.; Romani, A. M. Univ Girona; Wassercluster Lunz Biol Stn GmbH; Univ Vienna; Natl Res Council Italy IRSA CNR; Univ Barcelona Heterotrophic bacteria play a key role in the degradation of organic matter and carbon cycling in river sediments. These bacterial communities are directly influenced by environmental variables that differ spatially and temporally in rivers. Here, we studied the longitudinal patterns of sediment bacterial community composition and dissolved organic matter utilization under base flow and drought conditions in a Mediterranean river. Our results indicated that sediment microbial communities were affected by dissolved organic matter quality and origin along the river continuum. In headwaters the potential degradation of cellulose and hemicellulose was greater i.e., higher beta glucosidase and beta xylosidase activities , suggesting higher microbial utilization of allochthonous detritus from terrestrial origin. Conversely, the accumulation and transport of more recalcitrant compounds i.e., decrease in the recalcitrant index became potentially relevant downstream. Furthermore, discharge fluctuations had clear effects on bacterial community composition and dissolved organic matter use. The hydrological fragmentation of the river continuum during drought period generated sediment microhabitats dominated by gamma and delta Proteobacteria, with a greater potential capacity to degrade a wide range of compounds, particularly nitrogen containing moieties. During base flow conditions, we observed a higher occurrence of alpha Proteobacteria and a greater potential use of more recalcitrant carbon compounds, mostly of terrestrial origin. Overall, our findings suggest an upstream downstream longitudinal transition of sediment microbial communities that rely on allochthonous to autochthonous dissolved organic matter, and a shift toward autochthonous dissolved organic matter reliance during drought. 61 Published version https //aslopubs.onlinelibrary.wiley.com/doi/full/10.1002/lno.10308 Sediment microbial communities rely on different dissolved organic matter sources along a Mediterranean river continuum Sediment microbial communities rely on different dissolved organic matter sources along a Mediterranean river continuum Freixa et al. 2016_L O.pdf Articolo in rivista American Society of Limnology and Oceanography. 0024 3590 Limnology and oceanography Limnology and oceanography Limnol. oceanogr. Limnology and oceanography. stefano.fazi FAZI STEFANO stefano.amalfitano AMALFITANO STEFANO simona.crognale CROGNALE SIMONA