title: Shifts in microbial community structure and function in light- and dark-grown biofilms driven by warming.
abstract: Biofilms are dynamic players in biogeochemical cycling in running waters and are subjected to environmental stressors like those provoked by climate change. We investigated whether a 2°C increase in flowing water would affect prokaryotic community composition and heterotrophic metabolic activities of biofilms grown under light or dark conditions. Neither light nor temperature treatments were relevant for selecting a specific bacterial community at initial phases (7-day-old biofilms), but both variables affected the composition and function of mature biofilms (28-day-old). In dark-grown biofilms, changes in the prokaryotic community composition due to warming were mainly related to rotifer grazing, but no significant changes were observed in functional fingerprints. In light-grown biofilms, warming also affected protozoan densities, but its effect on prokaryotic density and composition was less evident. In contrast, heterotrophic metabolic activities in light-grown biofilms under warming showed a decrease in the functional diversity towards a specialized use of several carbohydrates. Results suggest that prokaryotes are functionally redundant in dark biofilms but functionally plastic in light biofilms. The more complex and self-serving light-grown biofilm determines a more buffered response to temperature than dark-grown biofilms. Despite the moderate increase in temperature of only 2°C, warming conditions drive significant changes in freshwater biofilms, which responded by finely tuning a complex network of interactions among microbial populations within the biofilm matrix.
authors.affiliation: Group of Continental Aquatic Ecology, University of Girona, Girona, Spain.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Romaní
authors.forename: Carles M
authors.initials: CM
authors.lastname: Borrego
authors.forename: Verónica
authors.initials: V
authors.lastname: Díaz-Villanueva
authors.forename: Anna
authors.initials: A
authors.lastname: Freixa
authors.forename: Frederic
authors.initials: F
authors.lastname: Gich
authors.forename: Irene
authors.initials: I
authors.lastname: Ylla
mesh_terms: D001419:Bacteria / Q000145:classification / Q000378:metabolism* / Q000528:radiation effects; D058491:Bacterial Load; D018441:Biofilms / Q000254:growth & development* / Q000528:radiation effects; D050260:Carbohydrate Metabolism; D005618:Fresh Water / Q000382:microbiology*; D052836:Heterotrophic Processes / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D059013:Microbial Consortia / Q000502:physiology* / Q000528:radiation effects; D010802:Phylogeny; D013696:Temperature