title: Temperature response of denitrification and anaerobic ammonium oxidation rates and microbial community structure in Arctic fjord sediments.
abstract: The temperature dependency of denitrification and anaerobic ammonium oxidation (anammox) rates from Arctic fjord sediments was investigated in a temperature gradient block incubator for temperatures ranging from -1 to 40°C. Community structure in intact sediments and slurry incubations was determined using Illumina SSU rRNA gene sequencing. The optimal temperature (Topt ) for denitrification was 25-27°C, whereas anammox rates were optimal at 12-17°C. Both denitrification and anammox exhibited temperature responses consistent with a psychrophilic community, but anammox bacteria may be more specialized for psychrophilic activity. Long-term (1-2 months) warming experiments indicated that temperature increases of 5-10°C above in situ had little effect on the microbial community structure or the temperature response of denitrification and anammox. Increases of 25°C shifted denitrification temperature responses to mesophilic with concurrent community shifts, and anammox activity was eliminated above 25°C. Additions of low molecular weight organic substrates (acetate and lactate) caused increases in denitrification rates, corroborating the hypothesis that the supply of organic substrates is a more dominant control of respiration rates than low temperature. These results suggest that climate-related changes in sinking particulate flux will likely alter rates of N removal more rapidly than warming.
authors.affiliation: Earth, Ocean, and Atmospheric Science Department, Florida State University, Tallahassee, FL, USA.
authors.forename: Andy
authors.initials: A
authors.lastname: Canion
authors.forename: Will A
authors.initials: WA
authors.lastname: Overholt
authors.forename: Joel E
authors.initials: JE
authors.lastname: Kostka
authors.forename: Markus
authors.initials: M
authors.lastname: Huettel
authors.forename: Gaute
authors.initials: G
authors.lastname: Lavik
authors.forename: Marcel M M
authors.initials: MM
authors.lastname: Kuypers
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism*; D000693:Anaerobiosis; D001105:Archaea / Q000145:classification / Q000302:isolation & purification; D001110:Arctic Regions; D001419:Bacteria / Q000145:classification / Q000302:isolation & purification; D002244:Carbon / Q000032:analysis; D057486:Carbon Cycle; D058440:Denitrification; D063366:Estuaries; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology*; D009584:Nitrogen / Q000032:analysis; D058458:Nitrogen Cycle; D010084:Oxidation-Reduction; D013696:Temperature
chemical_list: D064751:Ammonium Compounds; D002244:Carbon; D009584:Nitrogen