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  • 1
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    Modeling the impact of Krill on �Carbon Export Production in the Southern Ocean (2021)
    In:  EPIC3ICED Krill Workshop, 2021-05-18-2021-05-20
    Details
    Publication Date: 2022-03-14
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 2
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    Modelling the Role of Macrozooplankton in the Southern Ocean Biogeochemistry (2021)
    In:  EPIC3AMEMR (Advances in Marine Ecosystem Modelling Research) Symposium, 2021-07-12-2021-07-15
    Details
    Publication Date: 2022-03-14
    Description: In this study, we investigate the role of macrozooplankton in the biogeochemistry of the Southern Ocean using a three-dimensional global ocean ecosystem model (FESOM- REcoM2). The macrozooplankton group was parameterized according to characteristics of Antarctic krill and a related fast-sinking detritus class (larger particles, e.g. fecal pellets) was introduced in the model. It was then analyzed how the ecosystem structure and major carbon export pathways in the Southern Ocean changed through this extension of the model. The spatial distribution of macrozooplankton biomass in the Southern Ocean was reproduced reasonably well. Preliminary results showed that the zooplankton proportion of living compartments (phytoplankton and zooplankton groups) in the model increased. Thus, zooplankton contribution to the particulate organic carbon (POC) flux increased. The contribution of macrozooplankton to POC export at 100 m depth was 0.12 Pg C per year or 15% of total export in the Southern Ocean. The transfer efficiency of organic carbon nearly doubled and reached up to 50% in regions with high macrozooplankton biomass. These results emphasize the important role of macrozooplankton in the Southern Ocean carbon cycle and have implications for studies of the biological carbon pump.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 3
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    Sea-ice derived meltwater stratification slows the biological carbon pump: results from continuous observations (2021)
    In:  EPIC3Nature Communications, 12(1), pp. 7309
    Details
    Publication Date: 2022-01-07
    Description: The ocean moderates the world's climate through absorption of heat and carbon, but how much carbon the ocean will continue to absorb remains unknown. The North Atlantic Ocean west (Baffin Bay/Labrador Sea) and east (Fram Strait/Greenland Sea) of Greenland features the most intense absorption of anthropogenic carbon globally; the biological carbon pump (BCP) contributes substantially. As Arctic sea-ice melts, the BCP changes, impacting global climate and other critical ocean attributes (e.g. biodiversity). Full understanding requires year-round observations across a range of ice conditions. Here we present such observations: autonomously collected Eulerian continuous 24-month time-series in Fram Strait. We show that, compared to ice-unaffected conditions, sea-ice derived meltwater stratification slows the BCP by 4 months, a shift from an export to a retention system, with measurable impacts on benthic communities. This has implications for ecosystem dynamics in the future warmer Arctic where the seasonal ice zone is expected to expand.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
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    Iron and Manganese: major drivers of Southern Ocean phytoplankton ecology and productivity (2022)
    In:  EPIC3TOPIC 6 Symposium, 2022
    Details
    Publication Date: 2022-06-26
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 5
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    Impact of phytoplankton composition on carbon export in the southern Weddell Sea (2022)
    In:  EPIC3Gordon Research Conference, Hotel Don Jaime, Castelldefels, Spain, 2022-05-01-2022-05-06
    Details
    Publication Date: 2022-10-16
    Description: Climatic changes in the Southern Ocean have strong implications for the global marine carbon cycle, for example through changes in phytoplankton community composition. These shifts, in turn, can affect the strength and efficiency of the biological carbon pump, i.e. the process by which carbon is exported from the surface ocean to the deep sea via the aggregation and sinking of phytoplankton and other organic matter. At depth, carbon can be sequestered over long periods of time, effectively “buffering” increasing atmospheric CO2 concentrations. For the Southern Ocean, specifically the Weddell Sea, we only have limited data on carbon export due to the difficulties of accessing these remote and often ice-covered regions. Based on various phytoplankton bottle incubation experiments which simulated future climatic changes a possible shift in phytoplankton community composition from large diatoms to small flagellates such as Phaeocystis sp. is indicated, with unknown consequences for nutrient cycling and carbon export. To address these unknowns, we conducted in situ measurements and roller tank experiments with contrasting diatom-to-Phaeocystis ratios during a Polarstern cruise to the Southern Weddell Sea in spring 2021 to characterize aggregate formation degradation and sinking of marine snow. The same set of parameters were also assessed in controlled laboratory experiments with well-defined diatom-to-Phaeocystis ratios. Based on our results from field and laboratory, we hypothesised that a climate-mediated shift towards Phaeocystis in the future would reduce the efficiency of the biological carbon pump due to decreased silica-ballasting and increased concentrations of positively buoyant exopolymeric substances associated with Phaeocystis colonies. To our surprise, preliminary results reveal that higher Phaeocystis cell numbers relative to diatoms do not lead to a statistically significant reduction in aggregate mass density and size-specific sinking velocity. At the same time, there was a trend towards larger particles when Phaeocystis was abundant. Our results from field and laboratory observation together reveal that Phaeocystis-dominated communities do not impede carbon export in the Weddell Sea, but may actually enhance it.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 6
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    Machine learning techniques to characterize functional traits of plankton from image data (2022)
    Association for the Sciences of Limnology and Oceanography
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    Publication Date: 2022-10-18
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Orenstein, E., Ayata, S., Maps, F., Becker, É., Benedetti, F., Biard, T., Garidel‐Thoron, T., Ellen, J., Ferrario, F., Giering, S., Guy‐Haim, T., Hoebeke, L., Iversen, M., Kiørboe, T., Lalonde, J., Lana, A., Laviale, M., Lombard, F., Lorimer, T., Martini, S., Meyer, A., Möller, K.O., Niehoff, B., Ohman, M.D., Pradalier, C., Romagnan, J.-B., Schröder, S.-M., Sonnet, V., Sosik, H.M., Stemmann, L.S., Stock, M., Terbiyik-Kurt, T., Valcárcel-Pérez, N., Vilgrain, L., Wacquet, G., Waite, A.M., & Irisson, J. Machine learning techniques to characterize functional traits of plankton from image data. Limnology and Oceanography, 67(8), (2022): 1647-1669, https://doi.org/10.1002/lno.12101.
    Description: Plankton imaging systems supported by automated classification and analysis have improved ecologists' ability to observe aquatic ecosystems. Today, we are on the cusp of reliably tracking plankton populations with a suite of lab-based and in situ tools, collecting imaging data at unprecedentedly fine spatial and temporal scales. But these data have potential well beyond examining the abundances of different taxa; the individual images themselves contain a wealth of information on functional traits. Here, we outline traits that could be measured from image data, suggest machine learning and computer vision approaches to extract functional trait information from the images, and discuss promising avenues for novel studies. The approaches we discuss are data agnostic and are broadly applicable to imagery of other aquatic or terrestrial organisms.
    Description: SDA acknowledges funding from CNRS for her sabbatical in 2018–2020. Additional support was provided by the Institut des Sciences du Calcul et des Données (ISCD) of Sorbonne Université (SU) through the support of the sponsored junior team FORMAL (From ObseRving to Modeling oceAn Life), especially through the post-doctoral contract of EO. JOI acknowledges funding from the Belmont Forum, grant ANR-18-BELM-0003-01. French co-authors also wish to thank public taxpayers who fund their salaries. This work is a contribution to the scientific program of Québec Océan and the Takuvik Joint International Laboratory (UMI3376; CNRS - Université Laval). FM was supported by an NSERC Discovery Grant (RGPIN-2014-05433). MS is supported by the Research Foundation - Flanders (FWO17/PDO/067). FB received support from ETH Zürich. MDO is supported by the Gordon and Betty Moore Foundation and the U.S. National Science Foundation. ECB is supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) under the grant agreement no. 88882.438735/2019-01. TB is supported by the French National Research Agency (ANR-19-CE01-0006). NVP is supported by the Spanish State Research Agency, Ministry of Science and Innovation (PTA2016-12822-I). FL is supported by the Institut Universitaire de France (IUF). HMS was supported by the Simons Foundation (561126) and the U.S. National Science Foundation (CCF-1539256, OCE-1655686). Emily Peacock is gratefully acknowledged for expert annotation of IFCB images. LS was supported by the Chair VISION from CNRS/Sorbonne Université.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    Open ocean particle flux variability from surface to seafloor (2021)
    American Geophysical Union
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    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 Cael, B. B., Bisson, K., Conte, M., Duret, M. T., Follett, C. L., Henson, S. A., Honda, M. C., Iversen, M. H., Karl, D. M., Lampitt, R. S., Mouw, C. B., Muller-Karger, F., Pebody, C. A., Smith, K. L., & Talmy, D. Open ocean particle flux variability from surface to seafloor. Geophysical Research Letters, 48(9), (2021): e2021GL092895, https://doi.org/10.1029/2021GL092895.
    Description: The sinking of carbon fixed via net primary production (NPP) into the ocean interior is an important part of marine biogeochemical cycles. NPP measurements follow a log-normal probability distribution, meaning NPP variations can be simply described by two parameters despite NPP's complexity. By analyzing a global database of open ocean particle fluxes, we show that this log-normal probability distribution propagates into the variations of near-seafloor fluxes of particulate organic carbon (POC), calcium carbonate, and opal. Deep-sea particle fluxes at subtropical and temperate time-series sites follow the same log-normal probability distribution, strongly suggesting the log-normal description is robust and applies on multiple scales. This log-normality implies that 29% of the highest measurements are responsible for 71% of the total near-seafloor POC flux. We discuss possible causes for the dampening of variability from NPP to deep-sea POC flux, and present an updated relationship predicting POC flux from mineral flux and depth.
    Description: B. B. Cael and S. A. Henson acknowledge support from the National Environmental Research Council (NE/R015953/1) and the Horizon 2020 Framework Programme (820989, project COMFORT). The work reflects only the authors' views; the European Commission and their executive agency are not responsible for any use that may be made of the information the work contains. S. A. Henson also acknowledges support from a European Research Council Consolidator grant (GOCART, agreement number 724416). C. L. Follett acknowledges support from the Simons Foundation (grants #827829 and #553242). M. H. Iversen acknowledges support from the DFG-Research Center/Cluster of Excellence “The Ocean Floor – Earth's Uncharted Interface”: EXC-2077-390741603 and the HGF Young Investigator Group SeaPump “Seasonal and regional food web interactions with the biological pump”: VH-NG-1000. M. C. Honda acknowledges financial support from the Ministry of Education, Culture, Sports, Science, and Technology – Japan (grants #: KAKENHI JP18H04144 and JP19H05667). M. Conte acknowledges support from the US National Science Foundation, Division of Ocean Sciences for support for the Oceanic Flux Program time-series since inception, most recently by NSF OCE grant 1829885. D. M. Karl acknowledges support from the Gordon and Betty Moore Foundation (#3794) and the Simons Foundation (SCOPE #329108).
    Keywords: Ballast ; bathypelagic ; biogeochemistry ; log-normal ; particle flux ; variability
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
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    Vertical distribution of particulate matter in the Clarion Clipperton Zone (German Sector) - Potential impacts from deep-sea mining discharge in the water column (2022)
    In:  EPIC3Frontiers in Marine Science, 9(820947)
    Details
    Publication Date: 2022-08-15
    Description: Most studies on the potential impacts of deep-sea mining in the Clarion Clipperton Zone (CCZ) have largely focused on benthic ecosystems but ignore the pelagic environment. To model full-scale impacts, it is important to understand how sediment discharge might affect the pelagic zone as well. This study combines in situ optics, hydrography, and remote sensing to describe particle abundance and size distribution through the entire water column in the CCZ (German sector). CCZ surface waters were characterized as productive over the year. During the winter, we observed the formation of a sharp transition zone in Chla concentration, identifying the area as a productive transitional zone toward a more depleted ocean gyre. In the German sector, median particle size was small (±77 µm), and large particles (〉 300 µm) were rare. By assessing particle flux attenuation, we could show that the presence of a thick oxygen minimum zone (OMZ) plays an essential role in export and transformation of settling aggregates, with strong diel variations. We suggest that the combination of small aggregate size, bottom currents and slow seafloor consolidation may explain the extremely low sedimentation rate in the CCZ. We conclude that sediment incorporations and ballasting effect on settling particulate matter represent the most significant hazard on midwater and benthic ecosystems.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 9
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    Seasonal flux patterns and carbon transport from low-oxygen eddies at the Cape Verde Ocean Observatory: lessons learned from a time series sediment trap study (2009-2016) (2021)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Biogeosciences, COPERNICUS GESELLSCHAFT MBH, 18(24), pp. 6479-6500, ISSN: 1726-4170
    Details
    Publication Date: 2022-08-15
    Description: Mesoscale eddies are abundant in the eastern tropical North Atlantic and act as oases for phytoplankton growth due to local enrichment of nutrients in otherwise oligotrophic waters. It is not clear whether these eddies can efficiently transfer organic carbon and other flux components to depth and if they are important for the marine carbon budget. Due to their transient and regionally restricted nature, measurements of eddies' contribution to bathypelagic particle flux are difficult to obtain. Rare observations of export flux associated with low-oxygen eddies have suggested efficient export from the surface to the deep ocean, indicating that organic carbon flux attenuation might be low. Here we report on particle flux dynamics north of the Cabo Verde islands at the oligotrophic Cape Verde Ocean Observatory (CVOO; approx. 17∘35′ N, 24∘15′ W). The CVOO site is located in the preferred pathways of highly productive eddies that ultimately originate from the Mauritanian upwelling region. Between 2009 and 2016, we collected biogenic and lithogenic particle fluxes with sediment traps moored at ca. 1 and 3 km water depths at the CVOO site. From concurrent hydrography and oxygen observations, we confirm earlier findings that highly productive eddies are characterized by colder and less saline waters and a low-oxygen signal as well. Overall, we observed quite consistent seasonal flux patterns during the passage of highly productive eddies in the winters of 2010, 2012 and 2016. We found flux increases at 3 km depth during October–November when the eddies approached CVOO and distinct flux peaks during February–March.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 10
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    Secretion of sulphated fucans by diatoms may contribute to marine aggregate formation (2021)
    AMER SOC LIMNOLOGY OCEANOGRAPHY
    In:  EPIC3Limnology and Oceanography, AMER SOC LIMNOLOGY OCEANOGRAPHY, 66(10), pp. 3768-3782, ISSN: 0024-3590
    Details
    Publication Date: 2022-08-15
    Description: Microalgae produce copious amounts of structurally diverse polysaccharides, some are bound within cells and cell walls, while others are secreted into the surrounding seawater. A fraction of the secreted polysaccharides assembles into particles promoting aggregation and in turn formation of aggregates increases the export of carbon into the deep ocean via sinking. However, specific polysaccharides contributing to particle formation and carbon export remain unknown. Here, we studied microalgae polysaccharide composition in a system of reduced complexity consisting of lab grown monospecific cultures of the centric diatom species Thalassiosira weissflogii and Chaetoceros socialis. We followed the abundance and dynamics of five specific polysaccharide types in the dissolved and particulate organic matter (DOM and POM) for two weeks. Polysaccharides were detected using monoclonal antibodies (mAbs) specific for β-1,4-mannan, β-1,4-xylan, arabinogalactan, and two fucose-containing sulfated polysaccharide (FCSP) epitopes. Additionally, glycan composition of all samples was analyzed by monosaccharide analysis. The time series revealed polysaccharides partition differently between the dissolved and particulate carbon pools. β-1,4-xylan and β-1,4-mannan were mainly present in POM, possibly as cell wall polymers, while FCSPs were found in both DOM and POM. The data showed that the main glycan component secreted by diatoms was fucose-containing polysaccharide, which accumulated in DOM over time. Roller tank experiments were used to induce aggregate formation finding FCSP transitioned from DOM to POM under aggregating conditions. These results suggest that diatom-secreted FCSPs are involved in the formation of aggregates, which promote the formation of particles, and potentially carbon export.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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