Chironomus plumosus larvae increase fluxes of denitrification products and diversity of nitrate-reducing bacteria in freshwater sediment.
Benthic invertebrates affect microbial processes and communities in freshwater sediment by enhancing sediment-water solute fluxes and by grazing on bacteria. Using microcosms, the effects of larvae of the widespread midge Chironomus plumosus on the efflux of denitrification products (N2O and N2+N2O) and the diversity and abundance of nitrate- and nitrous-oxide-reducing bacteria were investigated. Additionally, the diversity of actively nitrate- and nitrous-oxide-reducing bacteria was analyzed in the larval gut. The presence of larvae increased the total effluxes of N2O and N2+N2O up to 8.6- and 4.2-fold, respectively, which was mostly due to stimulation of sedimentary denitrification; incomplete denitrification in the guts accounted for up to 20% of the N2O efflux. Phylotype richness of the nitrate reductase gene narG was significantly higher in sediment with than without larvae. In the gut, 47 narG phylotypes were found expressed, which may contribute to higher phylotype richness in colonized sediment. In contrast, phylotype richness of the nitrous oxide reductase gene nosZ was unaffected by the presence of larvae and very few nosZ phylotypes were expressed in the gut. Gene abundance of neither narG, nor nosZ was different in sediments with and without larvae. Hence, C. plumosus increases activity and diversity, but not overall abundance of nitrate-reducing bacteria, probably by providing additional ecological niches in its burrow and gut.
Department of Bioscience, Microbiology, Aarhus University, Ny Munkegade 114, 8000 Århus C, Denmark.
Morten
M
Poulsen
Department of Bioscience, Microbiology, Aarhus University, Ny Munkegade 114, 8000 Århus C, Denmark.
Michael V W
MV
Kofoed
Department of Bioscience, Microbiology, Aarhus University, Ny Munkegade 114, 8000 Århus C, Denmark.
Lone H
LH
Larsen
Department of Bioscience, Microbiology, Aarhus University, Ny Munkegade 114, 8000 Århus C, Denmark.
Andreas
A
Schramm
Department of Bioscience, Microbiology, Aarhus University, Ny Munkegade 114, 8000 Århus C, Denmark; Max-Planck-Institute for Marine Microbiology, Microsensor Group, Celsiusstraße 1, 28359 Bremen, Germany. Electronic address: peterstief@biology.sdu.dk.
Peter
P
Stief
D000818:Animals; D001419:Bacteria / Q000254:growth & development* / Q000378:metabolism*; D044822:Biodiversity; D002683:Chironomidae / Q000254:growth & development*; D058440:Denitrification; D005618:Fresh Water / Q000382:microbiology / Q000469:parasitology; D014644:Genetic Variation; D019015:Geologic Sediments / Q000382:microbiology* / Q000469:parasitology*; D007814:Larva / Q000254:growth & development; D050901:Nitrate Reductase / Q000235:genetics; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism; D010084:Oxidation-Reduction
D009566:Nitrates; D050901:Nitrate Reductase; D009609:Nitrous Oxide; D009584:Nitrogen
Bioturbation; Denitrification; Freshwater sediment; Functional gene; Gut bacteria; Macrofauna; Nitrous oxide; Phylotype richness