Santoro Alyson

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Last Name
Santoro
First Name
Alyson
ORCID
0000-0003-2503-8219

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Author: Casciotti, Karen L. ×

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Now showing 1 - 8 of 8
  • Article
    Nitrogen cycling in the secondary nitrite maximum of the eastern tropical North Pacific off Costa Rica
    (John Wiley & Sons, 2015-12-15) Buchwald, Carolyn ; Santoro, Alyson E. ; Stanley, Rachel H. R. ; Casciotti, Karen L.
    Nitrite is a central intermediate in the marine nitrogen cycle and represents a critical juncture where nitrogen can be reduced to the less bioavailable N2 gas or oxidized to nitrate and retained in a more bioavailable form. We present an analysis of rates of microbial nitrogen transformations in the oxygen deficient zone (ODZ) within the eastern tropical North Pacific Ocean (ETNP). We determined rates using a novel one-dimensional model using the distribution of nitrite and nitrate concentrations, along with their natural abundance nitrogen (N) and oxygen (O) isotope profiles. We predict rate profiles for nitrate reduction, nitrite reduction, and nitrite oxidation throughout the ODZ, as well as the contributions of anammox to nitrite reduction and nitrite oxidation. Nitrate reduction occurs at a maximum rate of 25 nM d−1 at the top of the ODZ, at the same depth as the maximum rate of nitrite reduction, 15 nM d−1. Nitrite oxidation occurs at maximum rates of 10 nM d−1 above the secondary nitrite maximum, but also in the secondary nitrite maximum, within the ODZ. Anammox contributes to nitrite oxidation within the ODZ but cannot account for all of it. Nitrite oxidation within the ODZ that is not through anammox is also supported by microbial gene abundance profiles. Our results suggest the presence of nitrite oxidation within the ETNP ODZ, with implications for the distribution and physiology of marine nitrite-oxidizing bacteria, and for total nitrogen loss in the largest marine ODZ.
  • Preprint
    Enrichment and characterization of ammonia-oxidizing archaea from the open ocean : phylogeny, physiology and stable isotope fractionation
    ( 2011-03-14) Santoro, Alyson E. ; Casciotti, Karen L.
    Archaeal genes for ammonia oxidation are widespread in the marine environment, but direct physiological evidence for ammonia oxidation by marine archaea is limited. We report the enrichment and characterization of three strains of pelagic ammonia-oxidizing archaea (AOA) from the north Pacific Ocean that have been maintained in laboratory culture for over three years. Phylogenetic analyses indicate the three strains belong to a previously identified clade of water column-associated AOA and possess 16S rRNA genes and ammonia monooxygenase subunit a (amoA) genes highly similar (98-99% identity) to those recovered in DNA and cDNA clone libraries from the open ocean. The strains grow in natural seawater-based liquid medium while stoichiometrically converting ammonium (NH4 +) to nitrite (NO2 -). Ammonia oxidation by the enrichments is only partially inhibited by allylthiourea at concentrations known to inhibit cultivated ammonia-oxidizing bacteria. The three strains were used to determine the nitrogen stable isotope effect (15εNH3) during archaeal ammonia oxidation, an important parameter for interpreting stable isotope ratios in the environment. Archaeal 15εNH3 ranged from 13- 41‰, within the range of that previously reported for ammonia-oxidizing bacteria. Despite low amino acid identity between the archaeal and bacterial Amo proteins, their functional diversity as captured by 15εNH3 is similar.
  • Dataset
    Dissolved nitrite and ammonium concentration data from R/V Atlantis (AT15-61) cruise in Jan-Feb 2010 and R/V Melville (MV1104) cruise in Mar-Apr 2011 in the Eastern Tropical South Pacific
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-05-07) Casciotti, Karen L. ; Santoro, Alyson E. ; Knapp, Angela N.
    Dissolved nitrite ([NO2-]) and ammonium ([NH4+]) concentration data were collected on two cruises in the Eastern Tropical South Pacific. Data from R/V Atlantis (AT15-61) cruise collected in Jan-Feb 2010 and data from R/V Melville (MV1104) cruise collected in Mar-Apr 2011 as part of the Microbial Nitrification project. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/820165
  • Dataset
    Processed CTD data from cruises R/V Atlantis (AT15-61) in Jan-Feb 2010 and R/V Melville (MV1104) in Mar-Apr 2011 in the Eastern Tropical South Pacific
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-05-07) Casciotti, Karen L. ; Capone, Douglas G. ; Santoro, Alyson E. ; Berelson, William M. ; Knapp, Angela N.
    Processed CTD data from cruises R/V Atlantis (AT15-61) in Jan-Feb 2010 and R/V Melville (MV1104) in Mar-Apr 2011 in the Eastern Tropical South Pacific For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/827861
  • Dataset
    Ammonia oxidation, nitrite oxidation, and nitrate reduction rates from R/V Atlantis (AT15-61) cruise in Jan-Feb 2010 and R/V Melville (MV1104) cruise in Mar-Apr 2011 in the Eastern Tropical South Pacific
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-05-07) Casciotti, Karen L. ; Santoro, Alyson E.
    Ammonia oxidation, nitrite oxidation, and nitrate reduction rates from cruises R/V Atlantis (AT15-61) in Jan-Feb 2010 and R/V Melville (MV1104) in Mar-Apr 2011 in the Eastern Tropical South Pacific For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/826782
  • Dataset
    Water column amoA and Nitrospina-like 16S rRNA gene abundances from qPCR in the Eastern Tropical South Pacific using seawater collected on R/V Atlantis (AT15-61) cruise in Jan-Feb 2010 and R/V Melville (MV1104) cruise in Mar-Apr 2011.
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-05-07) Casciotti, Karen L. ; Santoro, Alyson E.
    Water column amoA and Nitrospina-like 16S rRNA gene abundances from qPCR in the Eastern Tropical South Pacific using seawater collected on R/V Atlantis (AT15-61) cruise in Jan-Feb 2010 and R/V Melville (MV1104) cruise in Mar-Apr 2011. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/826781
  • Article
    Oxygen isotopic composition of nitrate and nitrite produced by nitrifying cocultures and natural marine assemblages
    (Association for the Sciences of Limnology and Oceanography, 2012-09) Buchwald, Carolyn ; Santoro, Alyson E. ; McIlvin, Matthew R. ; Casciotti, Karen L.
    The δ18O value of nitrate produced during nitrification (δ18ONO3,nit) was measured in experiments designed to mimic oceanic conditions, involving cocultures of ammonia-oxidizing bacteria or ammonia-oxidizing archaea and nitrite-oxidizing bacteria, as well as natural marine assemblages. The estimates of ranged from −1.5‰ ± 0.1‰ to +1.3‰ ± 1.4‰ at δ18O values of water (H2O) and dissolved oxygen (O2) of 0‰ and 24.2‰ vs. Vienna Standard Mean Ocean Water, respectively. Additions of 18O-enriched H2O allowed us to evaluate the effects of oxygen (O) isotope fractionation and exchange on . Kinetic isotope effects for the incorporation of O atoms were the most important factors for setting overall values relative to the substrates (O2 and H2O). These isotope effects ranged from +10‰ to +22‰ for ammonia oxidation (O2 plus H2O incorporation) and from +1‰ to +27‰ for incorporation of H2O during nitrite oxidation. values were also affected by the amount and duration of nitrite accumulation, which permitted abiotic O atom exchange between nitrite and H2O. Coculture incubations where ammonia oxidation and nitrite oxidation were tightly coupled showed low levels of nitrite accumulation and exchange (3% ± 4%). These experiments had values of −1.5‰ to +0.7‰. Field experiments had greater accumulation of nitrite and a higher amount of exchange (22% to 100%), yielding an average value of +1.9‰ ± 3.0‰. Low levels of biologically catalyzed exchange in coculture experiments may be representative of nitrification in much of the ocean where nitrite accumulation is low. Abiotic oxygen isotope exchange may be important where nitrite does accumulate, such as oceanic primary and secondary nitrite maxima.
  • Dataset
    Nitrous oxide (N2O) concentration data and associated physicochemical parameters from cruise AT15-61 in Jan-Feb 2010 and cruise MV1104 in Mar-Apr 2011 in the Eastern Tropical South Pacific
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-06-03) Casciotti, Karen L. ; Santoro, Alyson E.
    Nitrous oxide (N2O) concentration data and associated physicochemical parameters from the CTD sensor package collected on R/V Atlantis (AT15-61) cruise in Jan-Feb 2010 and R/V Melville (MV1104) cruise in Mar-Apr 2011 in the Eastern Tropical South Pacific. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/821268