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Hilary G.
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  • Dataset
    Particle bulk d15N values from EXPORTS cruises SR1812 on R/V Sally Ride and RR1813 on R/V Roger Revelle in August to September 2018
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2022-09-30) Wojtal, Paul K. ; Popp, Brian N. ; Close, Hilary G.
    This dataset includes d15N values of bulk nitrogen from size-fractionated and sinking particles collected on the EXPORTS cruises (SR1812 on R/V Sally Ride and RR1813 R/V Roger Revelle) in August to September 2018. 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/880376
  • Article
    Particulate organic carbon deconstructed: molecular and chemical composition of particulate organic carbon in the ocean
    (Frontiers Media, 2020-06-26) Kharbush, Jenan J. ; Close, Hilary G. ; Van Mooy, Benjamin A. S. ; Arnosti, Carol ; Smittenberg, Rienk H. ; Le Moigne, Frederic A. C. ; Mollenhauer, Gesine ; Scholz-Böttcher, Barbara ; Obreht, Igor ; Koch, Boris P. ; Becker, Kevin W. ; Iversen, Morten H. ; Mohr, Wiebke
    The dynamics of the particulate organic carbon (POC) pool in the ocean are central to the marine carbon cycle. POC is the link between surface primary production, the deep ocean, and sediments. The rate at which POC is degraded in the dark ocean can impact atmospheric CO2 concentration. Therefore, a central focus of marine organic geochemistry studies is to improve our understanding of POC distribution, composition, and cycling. The last few decades have seen improvements in analytical techniques that have greatly expanded what we can measure, both in terms of organic compound structural diversity and isotopic composition, and complementary molecular omics studies. Here we provide a brief overview of the autochthonous, allochthonous, and anthropogenic components comprising POC in the ocean. In addition, we highlight key needs for future research that will enable us to more effectively connect diverse data sources and link the identity and structural diversity of POC to its sources and transformation processes.
  • Dataset
    Size fractionated zooplankton d13C and d15N of individual amino acids from EXPORTS cruise RR1813 in August 2018
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2022-01-26) Popp, Brian N. ; Close, Hilary G.
    This dataset reports the size fractionated zooplankton d13C and d15N of individual amino acids from samples collected on the EXPORTS cruise (RR1813) in August 2018. 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/868193
  • Dataset
    Size fractionated zooplankton C:N, d13C, and d15N from the EXPORTS cruise on R/V Roger Revelle (RR1813) during August and September 2018
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-07-12) Popp, Brian N. ; Close, Hilary G.
    Size fractionated zooplankton C:N, d13C, and d15N from the EXPORTS cruise on R/V Roger Revelle (RR1813) during August and September 2018. Zooplankton were collected using a multiple opening-closing net and environmental sensing system (MOCNESS). 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/772776
  • Dataset
    Particle d15N values of amino acids from EXPORTS cruises SR1812 on R/V Sally Ride and RR1813 on R/V Roger Revelle in August to September 2018
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2022-09-30) Wojtal, Paul K. ; Popp, Brian N. ; Close, Hilary G.
    This dataset includes d15N values of individual amino acids from size-fractionated and sinking particles collected on the EXPORTS cruises (SR1812 on R/V Sally Ride and RR1813 R/V Roger Revelle) in August to September 2018. 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/880041
  • Dataset
    Size fractionated zooplankton, C:N, d13C, and d15N from RRS James Cook cruise JC214
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2022-09-20) Shea, Connor H. ; Popp, Brian N. ; Close, Hilary G.
    This dataset includes size fractionated zooplankton, C:N, d13C, and d15N from EXPORTS cruise JC214 on RRS James Cook from May to June 2021. 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/880448
  • Article
    Deconvolving mechanisms of particle flux attenuation using nitrogen isotope analyses of amino acids
    (Association for the Sciences of Limnology and Oceanography (ASLO), 2023-07-12) Wojtal, Paul K. ; Doherty, Shannon C. ; Shea, Connor H. ; Popp, Brian N. ; Benitez-Nelson, Claudia R. ; Buesseler, Kenneth O. ; Estapa, Margaret L. ; Roca-Marti, Montserrat ; Close, Hilary G.
    Particulate organic matter settling out of the euphotic zone is a major sink for atmospheric carbon dioxide and serves as a primary food source to mesopelagic food webs. Degradation of this organic matter encompasses a suite of mechanisms that attenuate flux, including heterotrophic metabolic processes of microbes and metazoans. The relative contributions of microbial and metazoan heterotrophy to flux attenuation, however, have been difficult to determine. We present results of compound specific nitrogen isotope analysis of amino acids of sinking particles from sediment traps and size-fractionated particles from in situ filtration between the surface and 500 m at Ocean Station Papa, collected during NASA EXPORTS (EXport Processes in the Ocean from RemoTe Sensing). With increasing depth, we observe: (1) that, based on the δ15N values of threonine, fecal pellets dominate the sinking particle flux and that attenuation of downward particle flux occurs largely via disaggregation in the upper mesopelagic; (2) an increasing trophic position of particles in the upper water column, reflecting increasing heterotrophic contributions to the nitrogen pool and the loss of particles via remineralization; and (3) increasing δ15N values of source amino acids in submicron and small (1–6 μm) particles, reflecting microbial particle solubilization. We further employ a Bayesian mixing model to estimate the relative proportions of fecal pellets, phytodetritus, and microbially degraded material in particles and compare these results and our interpretations of flux attenuation mechanisms to other, independent methods used during EXPORTS.
  • Working Paper
    EXPORTS Measurements and Protocols for the NE Pacific Campaign
    (NASA STI Program and Woods Hole Oceanographic Institution, 2021-02) Behrenfeld, Michael J. ; Benitez-Nelson, Claudia R. ; Boss, Emmanuel S. ; Brzezinski, Mark A. ; Buck, Kristen N. ; Buesseler, Ken O. ; Burd, Adrian B. ; Carlson, Craig A. ; Cassar, Nicolas ; Cetinić, Ivona ; Close, Hilary G. ; Craig, Susanne E. ; D'Asaro, Eric A. ; Durkin, Colleen A. ; Estapa, Margaret L. ; Fassbender, Andrea ; Fox, James ; Freeman, Scott ; Gifford, Scott M. ; Gong, Weida ; Graff, Jason R. ; Gray, Deric ; Guidi, Lionel ; Halsey, Kim ; Hansell, Dennis A. ; Haëntjens, Nils ; Horner, Tristan J. ; Jenkins, Bethany D. ; Jones, Janice L. ; Karp-Boss, Lee ; Kramer, Sasha J. ; Lam, Phoebe J. ; Lee, Craig M. ; Lee, Jong-Mi ; Liu, Shuting ; Mannino, Antonio ; Maas, Amy E. ; Marchal, Olivier ; Marchetti, Adrian ; McDonnell, Andrew M. P. ; McNair, Heather ; Menden-Deuer, Susanne ; Morison, Francoise ; Nelson, Norman B. ; Nicholson, David P. ; Niebergall, Alexandria K. ; Omand, Melissa M. ; Passow, Uta ; Perry, Mary J. ; Popp, Brian N. ; Proctor, Chris ; Rafter, Patrick ; Roca-Martí, Montserrat ; Roesler, Collin S. ; Rubin, Edwina ; Rynearson, Tatiana A. ; Santoro, Alyson E. ; Siegel, David A. ; Sosik, Heidi M. ; Soto Ramos, Inia ; Stamieszkin, Karen ; Steinberg, Deborah K. ; Stephens, Brandon M. ; Thompson, Andrew F. ; Van Mooy, Benjamin A. S. ; Zhang, Xiaodong
    EXport Processes in the Ocean from Remote Sensing (EXPORTS) is a large-scale NASA-led and NSF co-funded field campaign that will provide critical information for quantifying the export and fate of upper ocean net primary production (NPP) using satellite information and state of the art technology.
  • Article
    An operational overview of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) Northeast Pacific field deployment
    (University of California Press, 2021-07-07) Siegel, David A. ; Cetinić, Ivona ; Graff, Jason R. ; Lee, Craig M. ; Nelson, Norman B. ; Perry, Mary J. ; Soto Ramos, Inia ; Steinberg, Deborah K. ; Buesseler, Ken O. ; Hamme, Roberta C. ; Fassbender, Andrea ; Nicholson, David P. ; Omand, Melissa M. ; Robert, Marie ; Thompson, Andrew F. ; Amaral, Vinicius ; Behrenfeld, Michael J. ; Benitez-Nelson, Claudia R. ; Bisson, Kelsey ; Boss, Emmanuel S. ; Boyd, Philip ; Brzezinski, Mark A. ; Buck, Kristen N. ; Burd, Adrian B. ; Burns, Shannon ; Caprara, Salvatore ; Carlson, Craig A. ; Cassar, Nicolas ; Close, Hilary G. ; D'Asaro, Eric A. ; Durkin, Colleen A. ; Erickson, Zachary K. ; Estapa, Margaret L. ; Fields, Erik ; Fox, James ; Freeman, Scott ; Gifford, Scott M. ; Gong, Weida ; Gray, Deric ; Guidi, Lionel ; Haëntjens, Nils ; Halsey, Kim ; Huot, Yannick ; Hansell, Dennis A. ; Jenkins, Bethany D. ; Karp-Boss, Lee ; Kramer, Sasha J. ; Lam, Phoebe J. ; Lee, Jong-Mi ; Maas, Amy E. ; Marchal, Olivier ; Marchetti, Adrian ; McDonnell, Andrew M. P. ; McNair, Heather ; Menden-Deuer, Susanne ; Morison, Francoise ; Niebergall, Alexandria K. ; Passow, Uta ; Popp, Brian N. ; Potvin, Geneviève ; Resplandy, Laure ; Roca-Martí, Montserrat ; Roesler, Collin S. ; Rynearson, Tatiana A. ; Traylor, Shawnee ; Santoro, Alyson E. ; Seraphin, Kanesa ; Sosik, Heidi M. ; Stamieszkin, Karen ; Stephens, Brandon M. ; Tang, Weiyi ; Van Mooy, Benjamin ; Xiong, Yuanheng ; Zhang, Xiaodong
    The goal of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field campaign is to develop a predictive understanding of the export, fate, and carbon cycle impacts of global ocean net primary production. To accomplish this goal, observations of export flux pathways, plankton community composition, food web processes, and optical, physical, and biogeochemical (BGC) properties are needed over a range of ecosystem states. Here we introduce the first EXPORTS field deployment to Ocean Station Papa in the Northeast Pacific Ocean during summer of 2018, providing context for other papers in this special collection. The experiment was conducted with two ships: a Process Ship, focused on ecological rates, BGC fluxes, temporal changes in food web, and BGC and optical properties, that followed an instrumented Lagrangian float; and a Survey Ship that sampled BGC and optical properties in spatial patterns around the Process Ship. An array of autonomous underwater assets provided measurements over a range of spatial and temporal scales, and partnering programs and remote sensing observations provided additional observational context. The oceanographic setting was typical of late-summer conditions at Ocean Station Papa: a shallow mixed layer, strong vertical and weak horizontal gradients in hydrographic properties, sluggish sub-inertial currents, elevated macronutrient concentrations and low phytoplankton abundances. Although nutrient concentrations were consistent with previous observations, mixed layer chlorophyll was lower than typically observed, resulting in a deeper euphotic zone. Analyses of surface layer temperature and salinity found three distinct surface water types, allowing for diagnosis of whether observed changes were spatial or temporal. The 2018 EXPORTS field deployment is among the most comprehensive biological pump studies ever conducted. A second deployment to the North Atlantic Ocean occurred in spring 2021, which will be followed by focused work on data synthesis and modeling using the entire EXPORTS data set.
  • Article
    Variable carbon isotope fractionation of photosynthetic communities over depth in an open-ocean euphotic zone
    (National Academy of Sciences, 2024-02-26) Henderson, Lillian C. ; Wittmers, Fabian ; Carlson, Craig A. ; Worden, Alexandra Z. ; Close, Hilary G.
    Marine particulate organic carbon (POC) contributes to carbon export, food webs, and sediments, but uncertainties remain in its origins. Globally, variations in stable carbon isotope ratios (δ13C values) of POC between the upper and lower euphotic zones (LEZ) indicate either varying aspects of photosynthetic communities or degradative alteration of POC. During summertime in the subtropical north Atlantic Ocean, we find that δ13C values of the photosynthetic product phytol decreased by 6.3‰ and photosynthetic carbon isotope fractionation (εp) increased by 5.6‰ between the surface and the LEZ—variation as large as that found in the geologic record during major carbon cycle perturbations, but here reflecting vertical variation in δ13C values of photosynthetic communities. We find that simultaneous variations in light intensity and phytoplankton community composition over depth may be important factors not fully accounted for in common models of photosynthetic carbon isotope fractionation. Using additional isotopic and cell count data, we estimate that photosynthetic and non-photosynthetic material (heterotrophs or detritus) contribute relatively constant proportions of POC throughout the euphotic zone but are isotopically more distinct in the LEZ. As a result, the large vertical differences in εp result in significant, but smaller, differences in the δ13C values of total POC across the same depths (2.7‰). Vertical structuring of photosynthetic communities and export potential from the LEZ may vary across current and past ocean ecosystems; thus, LEZ photosynthesis may influence the exported and/or sedimentary δ13C values of both phytol and total organic carbon and affect interpretations of εp over geologic time.