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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 29 (2015): 175–193, doi:10.1002/2014GB004935.
    Description: The attenuation of sinking particle fluxes through the mesopelagic zone is an important process that controls the sequestration of carbon and the distribution of other elements throughout the oceans. Case studies at two contrasting sites, the oligotrophic regime of the Bermuda Atlantic Time-series Study (BATS) and the mesotrophic waters of the west Antarctic Peninsula (WAP) sector of the Southern Ocean, revealed large differences in the rates of particle-attached microbial respiration and the average sinking velocities of marine particles, two parameters that affect the transfer efficiency of particulate matter from the base of the euphotic zone into the deep ocean. Rapid average sinking velocities of 270 ± 150 m d−1 were observed along the WAP, whereas the average velocity was 49 ± 25 m d−1 at the BATS site. Respiration rates of particle-attached microbes were measured using novel RESPIRE (REspiration of Sinking Particles In the subsuRface ocEan) sediment traps that first intercepts sinking particles then incubates them in situ. RESPIRE experiments yielded flux-normalized respiration rates of 0.4 ± 0.1 day−1 at BATS when excluding an outlier of 1.52 day−1, while these rates were undetectable along the WAP (0.01 ± 0.02 day−1). At BATS, flux-normalized respiration rates decreased exponentially with respect to depth below the euphotic zone with a 75% reduction between the 150 and 500 m depths. These findings provide quantitative and mechanistic insights into the processes that control the transfer efficiency of particle flux through the mesopelagic and its variability throughout the global oceans.
    Description: Funding was provided by the University of Alaska Fairbanks, Woods Hole Oceanographic Institution (WHOI) Rinehart Access to the Sea Program, the WHOI Coastal Oceans Institute, WHOI Academic Programs Office, and the National Science Foundation (NSF) for support of PAL (ANT-0823101), FOODBANCS, and WAPflux (ANT- 83886600) projects. A grant from the NSF Carbon and Water Program (06028416) supported the development of these methods.
    Description: 2015-08-25
    Keywords: Biological pump ; Marine particles ; Carbon flux ; Sinking velocity ; Microbial respiration
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 32 (2018): 1312-1328, doi:10.1029/2018GB005934.
    Description: Ocean biological processes mediate the transport of roughly 10 petagrams of carbon from the surface to the deep ocean each year and thus play an important role in the global carbon cycle. Even so, the globally integrated rate of carbon export out of the surface ocean remains highly uncertain. Quantifying the processes underlying this biological carbon export requires a synthesis between model predictions and available observations of particulate organic carbon (POC) flux; yet the scale dissimilarities between models and observations make this synthesis difficult. Here we compare carbon export predictions from a mechanistic model with observations of POC fluxes from several data sets compiled from the literature spanning different space, time, and depth scales as well as using different observational methodologies. We optimize model parameters to provide the best match between model‐predicted and observed POC fluxes, explicitly accounting for sources of error associated with each data set. Model‐predicted globally integrated values of POC flux at the base of the euphotic layer range from 3.8 to 5.5 Pg C/year, depending on the data set used to optimize the model. Modeled carbon export pathways also vary depending on the data set used to optimize the model, as well as the satellite net primary production data product used to drive the model. These findings highlight the importance of collecting field data that average over the substantial natural temporal and spatial variability in carbon export fluxes, and advancing satellite algorithms for ocean net primary production, in order to improve predictions of biological carbon export.
    Description: NASA Ocean Biology and Biogeochemistry Program Grant Numbers: NNX16AR49G, NNXA122G, NNX16AR47G, OBB16_2‐0031; National Science Foundation
    Description: 2019-03-13
    Keywords: Carbon flux ; Remote sensing ; Carbon cycle ; Mechanistic model ; Optimization
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2017-01-04
    Description: Citation only. Published in Science 316: 567-570, doi: 10.1126/science.1137959
    Description: Funding was obtained primarily through the NSF, Ocean Sciences Programs in Chemical and Biological Oceanography, with additional support from the U.S. Department of Energy, Office of Science, Biological and Environmental Research Program, and other national programs, including the Australian Cooperative Research Centre program and Australian Antarctic Division.
    Keywords: Carbon flux ; Carbon sequestration ; Biological pump
    Repository Name: Woods Hole Open Access Server
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  • 4
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Estapa, M., Buesseler, K., Durkin, C. A., Omand, M., Benitez-Nelson, C. R., Roca-Marti, M., Breves, E., Kelly, R. P., & Pike, S. Biogenic sinking particle fluxes and sediment trap collection efficiency at Ocean Station Papa. Elementa: Science of the Anthropocene, 9(1), (2021): 00122, https://doi.org/10.1525/elementa.2020.00122.
    Description: Comprehensive field observations characterizing the biological carbon pump (BCP) provide the foundation needed to constrain mechanistic models of downward particulate organic carbon (POC) flux in the ocean. Sediment traps were deployed three times during the EXport Processes in the Ocean from RemoTe Sensing campaign at Ocean Station Papa in August–September 2018. We propose a new method to correct sediment trap sample contamination by zooplankton “swimmers.” We consider the advantages of polyacrylamide gel collectors to constrain swimmer influence and estimate the magnitude of possible trap biases. Measured sediment trap fluxes of thorium-234 are compared to water column measurements to assess trap performance and estimate the possible magnitude of fluxes by vertically migrating zooplankton that bypassed traps. We found generally low fluxes of sinking POC (1.38 ± 0.77 mmol C m–2 d–1 at 100 m, n = 9) that included high and variable contributions by rare, large particles. Sinking particle sizes generally decreased between 100 and 335 m. Measured 234Th fluxes were smaller than water column 234Th fluxes by a factor of approximately 3. Much of this difference was consistent with trap undersampling of both small (〈32 μm) and rare, large particles (〉1 mm) and with zooplankton active migrant fluxes. The fraction of net primary production exported below the euphotic zone (0.1% light level; Ez-ratio = 0.10 ± 0.06; ratio uncertainties are propagated from measurements with n = 7–9) was consistent with prior, late summer studies at Station P, as was the fraction of material exported to 100 m below the base of the euphotic zone (T100, 0.55 ± 0.35). While both the Ez-ratio and T100 parameters varied weekly, their product, which we interpret as overall BCP efficiency, was remarkably stable (0.055 ± 0.010), suggesting a tight coupling between production and recycling at Station P.
    Description: The authors would like to acknowledge funding support from the NASA EXPORTS program (Award 80NSSC17K0662) for all sediment trap data presented here. Net primary production data collection was supported by EXPORTS (Award 80NSSC17K568) to Oregon State University. Thorium data collection was supported by EXPORTS (Award 80NSSC17K0555) to KB, CRBN, and L. Resplandy.
    Keywords: Biological carbon pump ; Ocean Station Papa ; Sediment traps ; Carbon flux ; Particle size distribution ; Swimmers
    Repository Name: Woods Hole Open Access Server
    Type: Article
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