title: Effects of light and autochthonous carbon additions on microbial turnover of allochthonous organic carbon and community composition.
abstract: The fate of allochthonous dissolved organic carbon (DOC) in aquatic systems is primarily controlled by the turnover of heterotrophic bacteria. However, the roles that abiotic and biotic factors such as light and DOC release by aquatic primary producers play in the microbial decomposition of allochthonous DOC is not well understood. We therefore tested if light and autochthonous DOC additions would increase allochthonous DOC decomposition rates and change bacterial growth efficiencies and community composition (BCC). We established continuous growth cultures with different inocula of natural bacterial communities and alder leaf leachates (DOCleaf) with and without light exposure before amendment. Furthermore, we incubated DOCleaf together with autochthonous DOC from lysed phytoplankton cultures (DOCphyto). Our results revealed that pretreatments of DOCleaf with light resulted in a doubling of bacterial growth efficiency (BGE), whereas additions of DOCphyto or combined additions of DOCphyto and light had no effect on BGE. The change in BGE was not accompanied by shifts in the phylogenetic structure of the BCC, but BCC was influenced by the DOC source. Our results highlight that a doubling of BGE is not necessarily accompanied by a shift in BCC and that BCC is more strongly affected by resource properties.
authors.affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) Berlin, Experimental Limnology, Alte Fischerhütte 2, 16775, Stechlin, Germany, attermeyer@igb-berlin.de.
authors.forename: Katrin
authors.initials: K
authors.lastname: Attermeyer
authors.forename: Jörg
authors.initials: J
authors.lastname: Tittel
authors.forename: Martin
authors.initials: M
authors.lastname: Allgaier
authors.forename: Katharina
authors.initials: K
authors.lastname: Frindte
authors.forename: Christian
authors.initials: C
authors.lastname: Wurzbacher
authors.forename: Sabine
authors.initials: S
authors.lastname: Hilt
authors.forename: Norbert
authors.initials: N
authors.lastname: Kamjunke
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Grossart
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000254:growth & development; D002244:Carbon / Q000737:chemistry*; D004269:DNA, Bacterial / Q000235:genetics; D017753:Ecosystem; D008027:Light; D010802:Phylogeny; D010839:Phytoplankton / Q000254:growth & development / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D002244:Carbon