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  • Biological carbon pump  (7)
  • Thorium-234  (5)
  • Carbon flux  (4)
  • Particle flux  (4)
  • Sediment traps  (4)
  • 1
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    Particle fluxes associated with mesoscale eddies in the Sargasso Sea (2008)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 1426-1444, doi:10.1016/j.dsr2.2008.02.007.
    Description: We examined the impact of a cyclonic eddy and mode-water eddy on particle flux in the Sargasso Sea. The primary method used to quantify flux was based upon measurements of the natural radionuclide, 234Th, and these flux estimates were compared to results from sediment traps in both eddies, and a 210Po/210Pb flux method in the mode-water eddy. Particulate organic carbon (POC) fluxes at 150m ranged from 1 to 4 mmol C m-2 d-1 and were comparable between methods, especially considering differences in integration times scales of each approach. Our main conclusion is that relative to summer mean conditions at the Bermuda Atlantic Time-series Study (BATS) site, eddy-driven changes in biogeochemistry did not enhance local POC fluxes during this later, more mature stage of the eddy life cycle (〉6 months old). The absence of an enhancement in POC flux puts a constraint on the timing of higher POC flux events, which are thought to have caused the local O2 minima below each eddy, and must have taken place 〉2 months prior to our arrival. The mode-water eddy did enhance preferentially diatom biomass in its center where we estimated a factor of 3 times higher biogenic Si flux than the BATS summer average. An unexpected finding in the highly depth resolved 234Th data sets are narrow layers of particle export and remineralization within the eddy. In particular, a strong excess 234Th signal is seen below the deep chlorophyll maxima which we attribute to remineralization of 234Th bearing particles. At this depth below the euphotic zone, de novo particle production in the euphotic zone has stopped, yet particle remineralization continues via consumption of labile sinking material by bacteria and/or zooplankton. These data suggest that further study of processes in ocean layers is warranted not only within, but below the euphotic zone.
    Description: The EDDIES project was funded by the National Science Foundation Chemical, Biological, and Physical Oceanography Programs. Additional support for HPLC pigment analysis (Dr. Charles Trees, CHORS) was provided by NASA.
    Keywords: Oceanic eddies ; Particle flux ; Thorium-234
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 2
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    Changes in fecal pellet characteristics with depth as indicators of zooplankton repackaging of particles in the mesopelagic zone of the subtropical and subarctic North Pacific Ocean (2008)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 1636-1647, doi:10.1016/j.dsr2.2008.04.019.
    Description: We investigated how fecal pellet characteristics change with depth in order to quantify the extent of particle repackaging by mesopelagic zooplankton in two contrasting open-ocean systems. Material from neutrally buoyant sediment traps deployed in the summer of 2004 and 2005 at 150, 300, and 500 m was analyzed from both a mesotrophic (Japanese time-series station K2) and an oligotrophic (Hawaii Ocean Time series-HOT station ALOHA) environment in the Pacific Ocean as part of the VERtical Transport In the Global Ocean (VERTIGO) project. We quantified changes in the flux, size, shape, and color of particles recognizable as zooplankton fecal pellets to determine how these parameters varied with depth and location. Flux of K2 fecal pellet particulate organic carbon (POC) at 150 and 300 m was 4-5 times higher than at ALOHA, and at all depths, fecal pellets were 2-5 times larger at K2, reflective of the disparate zooplankton community structure at the two sites. At K2, the proportion of POC flux that consisted of fecal pellets generally decreased with depth from 20% at 150 m to 5% at 500 m, whereas at ALOHA this proportion increased with depth (and was more variable) from 14% to 35%. This difference in the fecal fraction of POC with increasing depth is hypothesized to be due to differences in the extent of zooplankton-mediated fragmentation (coprohexy) and in zooplankton community structure between the two locations. Both regions provided indications of sinking particle repackaging and zooplankton carnivory in the mesopelagic. At ALOHA this was reflected in a significant increase in the mean flux of larvacean fecal pellets from 150 to 500 m of 3 to 46 μg C m-2 d-1, respectively, and at K2 a large peak in larvacean mean pellet flux at 300 m of 3.1 mg C m-2 d-1. Peaks in red pellets produced by carnivores occurred at 300 m at K2, and a variety of other fecal pellet classes showed significant changes in their distribution with depth. There was also evidence of substantially higher pellet fragmentation at K2 with nearly double the ratio of broken:intact pellets at 150 and 300 m (mean of 67% and 64%, respectively ) than at ALOHA where the proportion of broken pellets remained constant with depth (mean 35%). Variations in zooplankton size and community structure within the mesopelagic zone can thus differentially alter the transfer efficiency of sinking POC.
    Description: This study was supported by grants from the U.S. National Science Foundation NSF OCE-0324402 (Biological Oceanography) to D.K.S and OCE-0301139 (Chemical Oceanography) to K.O.B.
    Keywords: Fecal pellets ; Mesopelagic ; Particle flux ; Zooplankton
    Repository Name: Woods Hole Open Access Server
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  • 3
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    Observations of carbon export by small sinking particles in the upper mesopelagic (2015)
    Elsevier
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Chemistry 175 (2015): 72-81, doi:10.1016/j.marchem.2015.02.011.
    Description: Carbon and nutrients are transported out of the surface ocean and sequestered at depth by sinking particles. Sinking particle sizes span many orders of magnitude and the relative influence of small particles on carbon export compared to large particles has not been resolved. To determine the influence of particle size on carbon export, the flux of both small (11–64 μm) and large (〉 64 μm) particles in the upper mesopelagic was examined during 5 cruises of the Bermuda Atlantic Time Series (BATS) in the Sargasso Sea using neutrally buoyant sediment traps mounted with tubes containing polyacrylamide gel layers and tubes containing a poisoned brine layer. Particles were also collected in surface-tethered, free-floating traps at higher carbon flux locations in the tropical and subtropical South Atlantic Ocean. Particle sizes spanning three orders of magnitude were resolved in gel samples, included sinking particles as small as 11 μm. At BATS, the number flux of small particles tended to increase with depth, whereas the number flux of large particles tended to decrease with depth. The carbon content of different sized particles could not be modeled by a single set of parameters because the particle composition varied across locations and over time. The modeled carbon flux by small particles at BATS, including all samples and depths, was 39 ± 20% of the modeled total carbon flux, and the percentage increased with depth in 4 out of the 5 months sampled. These results indicate that small particles (〈 64 μm) are actively settling in the water column and are an important contributor to carbon flux throughout the mesopelagic. Observations and models that overlook these particles will underestimate the vertical flux of organic matter in the ocean.
    Description: Funding for this study was provided by the National Science Foundation Chemical Oceanography Program (OCE-1260001 and 1406552 to M. L. Estapa) and the Woods Hole Oceanographic Institution Devonshire Postdoctoral Scholarship awarded to C. A. Durkin. Funding for the DeepDOM cruise was provided by the National Science Foundation Chemical Oceanography Program (OCE-1154320 to E. B. Kujawinski and K. Longnecker, WHOI).
    Keywords: Particle size ; Particle settling ; Carbon cycle ; Sediment traps ; Mesopelagic zone
    Repository Name: Woods Hole Open Access Server
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  • 4
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    High particle export over the continental shelf of the west Antarctic Peninsula (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 37 (2010): L22606, doi:10.1029/2010GL045448.
    Description: Drifting cylindrical traps and the flux proxy 234Th indicate more than an order of magnitude higher sinking fluxes of particulate carbon and 234Th in January 2009 than measured by a time-series conical trap used regularly on the shelf of the west Antarctic Peninsula (WAP). The higher fluxes measured in this study have several implications for our understanding of the WAP ecosystem. Larger sinking fluxes result in a revised export efficiency of at least 10% (C flux/net primary production) and a requisite lower regeneration efficiency in surface waters. High fluxes also result in a large supply of sinking organic matter to support subsurface and benthic food webs on the continental shelf. These new findings call into question the magnitude of seasonal and interannual variability in particle flux and reaffirm the difficulty of using moored conical traps as a quantitative flux collector in shallow waters.
    Description: Funding was provided by the WHOI Rinehart Access to the Sea program, the WHOI Coastal Oceans Institute, WHOI Academic Programs Office, and most significantly, from the NSF Office of Polar Programs for the PAL‐LTER (OPP 0823101), FOODBANCS and WAP Flux projects (OPP 0838866).
    Keywords: Particle export ; Sediment trap ; Thorium-234
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Effects of sinking velocities and microbial respiration rates on the attenuation of particulate carbon fluxes through the mesopelagic zone (2015)
    John Wiley & Sons
    Details
    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
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  • 6
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    How data set characteristics influence ocean carbon export models (2018)
    John Wiley & Sons
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    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
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  • 7
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    Revisiting carbon flux through the ocean's twilight zone (2010)
    American Association for the Advancement of Science
    Details
    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
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  • 8
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    Adsorbers for in-situ collection and at-sea gamma analysis of dissolved Thorium-234 in seawater (2006)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: Two polypropylene cartridge types (Beta Pure and Hytrex II) were tested in the laboratory as adsorbers for in-situ collection of dissolved Thorium-234 (234TH) in seawater. Using a uranyl nitrate tracer, we determined that a Mn02 impregnated 3.25-inch Hytrex II cartridge with a flow rate of 8 liters/minute would collect 234TH with a greater than 60% effciency. The smaller size and composition of the 3.25 inch Hytrex II cartridge enabled it to be pressed into a permanent 1-inch "puck" for direct gamma counting. This protocol significantly reduced the handling between collection and counting. When field tested in the Gulf of Maine as a large volume (〉500 liters) collector, the new adsorbers produced a greater than 80% collection effciency and a dissolved 234TH concentration which was consistent with independent samples collected at the same station and depth. These adsorbers were used successfully for the in-situ collection of 234TH in large volumes of seawater during the 1992 NOAA and NSF sponsored JGOFS EqPac program, with a mean collection efficiency of 0.79 +/- 9% (n=104 cartridge pairs).
    Description: Funding was provided by the National Oceanic and Atmospheric Administration Offce of Global Programs under Contract OCE-920395200.
    Keywords: Thorium-234 ; Mn02 adsorber ; seawater ; Cape Hatteras (Ship) Cruise ; Malcolm Baldridge (Ship) Cruise ; Discoverer (Ship) Cruise
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 9
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    Flux of particulate elements in the North Atlantic Ocean constrained by multiple radionuclides (2019)
    American Geophysical Union
    Details
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2019. 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(12), (2019): 1738-1758, doi:10.1029/2018GB005994.
    Description: Sinking particles strongly regulate the distribution of reactive chemical substances in the ocean, including particulate organic carbon and other elements (e.g., P, Cd, Mn, Cu, Co, Fe, Al, and 232Th). Yet, the sinking fluxes of trace elements have not been well described in the global ocean. The U.S. GEOTRACES campaign in the North Atlantic (GA03) offers the first data set in which the sinking flux of carbon and trace elements can be derived using four different radionuclide pairs (238U:234Th ;210Pb:210Po; 228Ra:228Th; and 234U:230Th) at stations co‐located with sediment trap fluxes for comparison. Particulate organic carbon, particulate P, and particulate Cd fluxes all decrease sharply with depth below the euphotic zone. Particulate Mn, Cu, and Co flux profiles display mixed behavior, some cases reflecting biotic remineralization, and other cases showing increased flux with depth. The latter may be related to either lateral input of lithogenic material or increased scavenging onto particles. Lastly, particulate Fe fluxes resemble fluxes of Al and 232Th, which all have increasing flux with depth, indicating a dominance of lithogenic flux at depth by resuspended sediment transported laterally to the study site. In comparing flux estimates derived using different isotope pairs, differences result from different timescales of integration and particle size fractionation effects. The range in flux estimates produced by different methods provides a robust constraint on the true removal fluxes, taking into consideration the independent uncertainties associated with each method. These estimates will be valuable targets for biogeochemical modeling and may also offer insight into particle sinking processes.
    Description: This study grew out of a synthesis workshop at the Lamont‐Doherty Earth Observatory of Columbia University in August 2016. This workshop was sponsored by the U.S. GEOTRACES Project Office (NSF 1536294) and the Ocean Carbon and Biogeochemistry (OCP) Project Office (NSF 1558412 and NASA NNX17AB17G). The U.S. National Science Foundation supported all of the analytical work on GA03. Kuanbo Zhou measured 228Th in the large size class particles (NSF 0925158 to WHOI). NSF 1061128 to Stony Brook University supported the BaRFlux project, for which Chistina Heilbrun is acknowledged for laboratory and field work. The lead author acknowledges support from a start‐up grant from the University of Southern Mississippi. Two anonymous reviewers are thanked for their constructive comments. All GEOTRACES GA03 data used in this study are accessible through the Biological and Chemical Oceanography Data Management Office (http://data.bco‐dmo.org/jg/dir/BCO/GEOTRACES/NorthAtlanticTransect/), and derived parameters are reported in the supporting information.
    Description: 2019-05-22
    Keywords: Biological carbon pump ; Trace metals ; North Atlantic ; Export ; GEOTRACES
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  • 10
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    A visual tour of carbon export by sinking particles (2022)
    American Geophysical Union
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    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Durkin, C. A., Buesseler, K. O., Cetinic, I., Estapa, M. L., Kelly, R. P., & Omand, M. A visual tour of carbon export by sinking particles. Global Biogeochemical Cycles, 35(10), (2021): e2021GB006985, https://doi.org/10.1029/2021GB006985.
    Description: To better quantify the ocean's biological carbon pump, we resolved the diversity of sinking particles that transport carbon into the ocean's interior, their contribution to carbon export, and their attenuation with depth. Sinking particles collected in sediment trap gel layers from four distinct ocean ecosystems were imaged, measured, and classified. The size and identity of particles was used to model their contribution to particulate organic carbon (POC) flux. Measured POC fluxes were reasonably predicted by particle images. Nine particle types were identified, and most of the compositional variability was driven by the relative contribution of aggregates, long cylindrical fecal pellets, and salp fecal pellets. While particle composition varied across locations and seasons, the entire range of compositions was measured at a single well-observed location in the subarctic North Pacific over one month, across 500 m of depth. The magnitude of POC flux was not consistently associated with a dominant particle class, but particle classes did influence flux attenuation. Long fecal pellets attenuated most rapidly with depth whereas certain other classes attenuated little or not at all with depth. Small particles (〈100 μm) consistently contributed ∼5% to total POC flux in samples with higher magnitude fluxes. The relative importance of these small particle classes (spherical mini pellets, short oval fecal pellets, and dense detritus) increased in low flux environments (up to 46% of total POC flux). Imaging approaches that resolve large variations in particle composition across ocean basins, depth, and time will help to better parameterize biological carbon pump models.
    Description: This work was supported by an NSF EAGER award to C. A. Durkin (OCE-1703664), M. L. Estapa (OCE-1703422), and M. Omand (OCE-1703336), and also by the NASA EXPORTS program (80NSSC17K0662), a NASA New Investigator award to M. L. Estapa (NNX14AM01G), the Rhode Island Endeavor Program (RIEP), NASA's PACE mission, and the Schmidt Ocean Institute.
    Keywords: Biological carbon pump ; Sediment traps ; Fecal pellets ; Aggregates ; Particles ; Salp
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