title: Water column anammox and denitrification in a temperate permanently stratified lake (Lake Rassnitzer, Germany).
abstract: We studied microbial N(2) production via anammox and denitrification in the anoxic water column of a restored mining pit lake in Germany over an annual cycle. We obtained high-resolution hydrochemical profiles using a continuous pumping sampler. Lake Rassnitzer is permanently stratified at ca. 29m depth, entraining anoxic water below a saline density gradient. Mixed-layer nitrate concentrations averaged ca. 200 micromol L(-1), but decreased to zero in the anoxic bottom waters. In contrast, ammonium was <5 micromol L(-1) in the mixed layer but increased in the anoxic waters to ca. 600 micromol L(-1) near the sediments. In January and October, (15)N tracer measurements detected anammox activity (maximum 504 nmol N(2)L(-1)d(-1) in (15)NH(4)(+)-amended incubations), but no denitrification. In contrast, in May, N(2) production was dominated by denitrification (maximum 74 nmol N(2)L(-1)d(-1)). Anammox activity in May was significantly lower than in October, as characterized by anammox rates (maximum 6 vs. 16 nmol N(2)L(-1)d(-1) in incubations with (15)NO(3)(-)), as well as relative and absolute anammox bacterial cell abundances (0.56% vs. 0.98% of all bacteria, and 2.7x10(4) vs. 5.2x10(4)anammox cells mL(-1), respectively) (quantified by catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) with anammox bacteria-specific probes). Anammox bacterial diversity was investigated with anammox bacteria-specific 16S rRNA gene clone libraries. The majority of anammox bacterial sequences were related to the widespread Candidatus Scalindua sorokinii/brodae cluster. However, we also found sequences related to Candidatus S. wagneri and Candidatus Brocadia fulgida, which suggests a high anammox bacterial diversity in this lake comparable with estuarine sediments.
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany. rhamersley@soka.edu
authors.forename: M Robert
authors.initials: MR
authors.lastname: Hamersley
authors.forename: Dagmar
authors.initials: D
authors.lastname: Woebken
authors.forename: Bertram
authors.initials: B
authors.lastname: Boehrer
authors.forename: Martin
authors.initials: M
authors.lastname: Schultze
authors.forename: Gaute
authors.initials: G
authors.lastname: Lavik
authors.forename: Marcel M M
authors.initials: MM
authors.lastname: Kuypers
mesh_terms: D001421:Bacteria, Anaerobic / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D005618:Fresh Water / Q000382:microbiology*; D005858:Germany; D017404:In Situ Hybridization, Fluorescence; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000378:metabolism; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D010802:Phylogeny; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012621:Seasons; D013696:Temperature; D014871:Water Microbiology
chemical_list: D004269:DNA, Bacterial; D009587:Nitrogen Isotopes; D000644:Quaternary Ammonium Compounds; D012336:RNA, Ribosomal, 16S; D009584:Nitrogen