title: Contribution of ammonia oxidation to chemoautotrophy in Antarctic coastal waters.
abstract: There are few measurements of nitrification in polar regions, yet geochemical evidence suggests that it is significant, and chemoautotrophy supported by nitrification has been suggested as an important contribution to prokaryotic production during the polar winter. This study reports seasonal ammonia oxidation (AO) rates, gene and transcript abundance in continental shelf waters west of the Antarctic Peninsula, where Thaumarchaeota strongly dominate populations of ammonia-oxidizing organisms. Higher AO rates were observed in the late winter surface mixed layer compared with the same water mass sampled during summer (mean±s.e.: 62±16 versus 13±2.8 nm per day, t-test P<0.0005). AO rates in the circumpolar deep water did not differ between seasons (21±5.7 versus 24±6.6 nm per day; P=0.83), despite 5- to 20-fold greater Thaumarchaeota abundance during summer. AO rates correlated with concentrations of Archaea ammonia monooxygenase (amoA) genes during summer, but not with concentrations of Archaea amoA transcripts, or with ratios of Archaea amoA transcripts per gene, or with concentrations of Betaproteobacterial amoA genes or transcripts. The AO rates we report (<0.1-220 nm per day) are ~10-fold greater than reported previously for Antarctic waters and suggest that inclusion of Antarctic coastal waters in global estimates of oceanic nitrification could increase global rate estimates by ~9%. Chemoautotrophic carbon fixation supported by AO was 3-6% of annualized phytoplankton primary production and production of Thaumarchaeota biomass supported by AO could account for ~9% of the bacterioplankton production measured in winter. Growth rates of thaumarchaeote populations inferred from AO rates averaged 0.3 per day and ranged from 0.01 to 2.1 per day.
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA, USA.|Department of Microbiology, University of Georgia, Athens, GA, USA.
authors.forename: Bradley B
authors.initials: BB
authors.lastname: Tolar
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA, USA.
authors.forename: Meredith J
authors.initials: MJ
authors.lastname: Ross
authors.affiliation: Department of Geology and Geophysics, University of Hawai'i, Honolulu, HI, USA.
authors.forename: Natalie J
authors.initials: NJ
authors.lastname: Wallsgrove
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Scripps Institution of Oceanography, UC San Diego, La Jolla, CA, USA.
authors.forename: Lihini I
authors.initials: LI
authors.lastname: Aluwihare
authors.affiliation: Department of Geology and Geophysics, University of Hawai'i, Honolulu, HI, USA.
authors.forename: Brian N
authors.initials: BN
authors.lastname: Popp
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA, USA.
authors.forename: James T
authors.initials: JT
authors.lastname: Hollibaugh
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D000864:Antarctic Regions; D001105:Archaea / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D052837:Chemoautotrophic Growth; D019766:Genes, Archaeal; D058465:Nitrification; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D012621:Seasons; D012623:Seawater / Q000382:microbiology*
chemical_list: D000641:Ammonia; D010088:Oxidoreductases; C045582:ammonia monooxygenase