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  • 1
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    Bacterial Colonization and Vertical Distribution of Marine Gel Particles (TEP and CSP) in the Arctic Fram Strait (2017)
    Frontiers
    In:  Frontiers in Marine Science, 4 (Art.No. 166).
    Details
    Publication Date: 2020-02-06
    Description: Gel particles—a class of abundant transparent organic particles—have increasingly gathered attention in marine research. Field studies on the bacterial colonization of marine gels however are still scarce. So far, most studies on respective particles have focused on the upper ocean, while little is known on their occurrence in the deep sea. Here, we report on the vertical distribution of the two most common gel particle types, which are polysaccharide-containing transparent exopolymer particles (TEP) and proteinaceous Coomassie stainable particles (CSP), as well as numbers of bacteria attached to gel particles throughout the water column, from the surface ocean down to the bathypelagial (〈 3,000 m). Our study was conducted in the Arctic Fram Strait during northern hemispheres' summer in 2015. Besides data on the bacterial colonization of the two gel particle types (TEP and CSP), we present bacterial densities on different gel particle size classes according to 12 different sampling depths at four sampling locations. Gel particles were frequently abundant at all sampled depths, and their concentrations decreased from the euphotic zone to the dark ocean. They were colonized by bacteria at all sampled water depths with risen importance at the deepest water layers, where fractions of bacteria attached to gel particles (%) increased within the total bacterial community. Due to the omnipresent bacterial colonization of gel particles at all sampled depths in our study, we presume that euphotic production of this type of organic matter may affect microbial species distribution within the whole water column in the Fram Strait, down to the deep sea. Our results raise the question if changes in the bacterial community composition and functioning on gel particles occur over depth, which may affect microbial respiration and remineralization rates of respective particles in different water layers.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.3389/fmars.2017.00166
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Sinking Organic Particles in the Ocean—Flux Estimates From in situ Optical Devices (2020)
    Frontiers
    Details
    Publication Date: 2023-02-08
    Description: Optical particle measurements are emerging as an important technique for understanding the ocean carbon cycle, including contributions to estimates of their downward flux, which sequesters carbon dioxide (CO2) in the deep sea. Optical instruments can be used from ships or installed on autonomous platforms, delivering much greater spatial and temporal coverage of particles in the mesopelagic zone of the ocean than traditional techniques, such as sediment traps. Technologies to image particles have advanced greatly over the last two decades, but the quantitative translation of these immense datasets into biogeochemical properties remains a challenge. In particular, advances are needed to enable the optimal translation of imaged objects into carbon content and sinking velocities. In addition, different devices often measure different optical properties, leading to difficulties in comparing results. Here we provide a practical overview of the challenges and potential of using these instruments, as a step toward improvement and expansion of their applications.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Particulate Organic Carbon Deconstructed: Molecular and Chemical Composition of Particulate Organic Carbon in the Ocean (2020)
    Frontiers
    Details
    Publication Date: 2023-02-08
    Description: 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.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Globally Consistent Quantitative Observations of Planktonic Ecosystems (2019)
    Frontiers
    In:  Frontiers in Marine Science, 6 . Art.Nr. 196.
    Details
    Publication Date: 2022-01-31
    Description: In this paper we review on the technologies available to make globally quantitative observations of particles, in general, and plankton, in particular, in the world oceans, and for sizes varying from sub-micron to centimeters. Some of these technologies have been available for years while others have only recently emerged. Use of these technologies is critical to improve understanding of the processes that control abundances, distributions and composition of plankton, provide data necessary to constrain and improve ecosystem and biogeochemical models, and forecast changes in marine ecosystems in light of climate change. In this paper we begin by providing the motivation for plankton observations, quantification and diversity qualification on a global scale. We then expand on the state-of-the-art, detailing a variety of relevant and (mostly) mature technologies and measurements, including bulk measurements of plankton, pigment composition, uses of genomic, optical, acoustical methods and analysis using particles counters, flow cytometers and quantitative imaging devices. We follow by highlighting the requirements necessary for a plankton observing system, the approach to achieve it and associated challenges. We conclude with ranked action-item recommendations for the next ten years to move towards our vision of a holistic ocean-wide plankton observing system. Particularly, we suggest to begin with a demonstration project on a GO-SHIP line and/or a long-term observation site and expand from there ensuring that issues associated with methods, observation tools, data analysis, quality assessment and curation are addressed early in the implementation. Global coordination is key for the success of this vision and will bring new insights on processes associated with nutrient regeneration, ocean production, fisheries, and carbon sequestration.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3389/fmars.2019.00196
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Editorial: Zooplankton and nekton: gatekeepers of the biological pump, volume II (2023)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Zooplankton and nekton organisms play multifaceted roles in marine ecosystems and are integral components of the ocean’s food web. By consuming a wide range of planktonic organisms and detrital matter, they directly impact the size-distribution of particles in the ocean by breaking large aggregates down to smaller fragments and by repackaging single phytoplankton cells into dense fecal pellets. Many zooplankton and nekton organisms also conduct diel vertical migrations (DVM). They ascend to the surface layer of the ocean at dusk to feed during the dark hours and return to midwater depths at dawn to hide from visual predation. As they metabolize and excrete organic material in deeper waters, they contribute to an “active flux” of carbon and nutrients. This active flux can have a substantial impact on the functioning of the biological pump — the process responsible for the downward export of carbon and nutrients into the ocean’s interior. In essence, zooplankton and nekton are gatekeepers of the biological pump via their diverse roles in particle dynamics, from consumption and fragmentation to the active transport of organic matter. Understanding these roles is critical for unraveling the complex mechanisms that govern the health and functioning of marine ecosystems, as well as for improving our models of global biogeochemical processes in the world’s oceans.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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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)
    Frontiers
    Details
    Publication Date: 2024-02-07
    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.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    A Novel Measurement-Based Model for Calculating Diffusive Fluxes Across Substrate-Water Interfaces of Marine Aggregates, Sediments and Biofilms (2021)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Our understanding of the small-scale processes that drive global biogeochemical cycles and the Earth’s climate is dependent on accurate estimations of interfacial diffusive fluxes to and from biologically-active substrates in aquatic environments. In this study, we present a novel model approach for accurate calculations of diffusive fluxes of dissolved gases, nutrients, and solutes from concentration profiles measured across the substrate-water interfaces using microsensors. The model offers a robust computational scheme for automatized determination of the interface position and enables precise calculations of the interfacial diffusive fluxes simultaneously. In contrast to other methods, the new approach is not restricted to any particular substrate geometry, does not require a priori determination of the interface position for the flux calculation, and, thus, reduces the uncertainties in calculated fluxes arising from partly subjective identification of the interface position. In addition, it is robust when applied to measured profiles containing scattered data points and insensitive to reasonable decreases of the spatial resolution of the data points. The latter feature allows for significantly reducing measurement time which is a crucial factor for in situ experiments.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Bacterial Colonization and Vertical Distribution of Marine Gel Particles (TEP and CSP) in the Arctic Fram Strait (2017)
    Frontiers
    In:  EPIC3Frontiers in Marine Science, Frontiers, 4(166), pp. 1-14, ISSN: 2296-7745
    Details
    Publication Date: 2017-07-03
    Description: Gel particles—a class of abundant transparent organic particles—have increasingly gathered attention in marine research. Field studies on the bacterial colonization of marine gels however are still scarce. So far, most studies on respective particles have focused on the upper ocean, while little is known on their occurrence in the deep sea. Here, we report on the vertical distribution of the two most common gel particle types, which are polysaccharide-containing transparent exopolymer particles (TEP) and proteinaceous Coomassie stainable particles (CSP), as well as numbers of bacteria attached to gel particles throughout the water column, from the surface ocean down to the bathypelagial (〈 3,000 m). Our study was conducted in the Arctic Fram Strait during northern hemispheres' summer in 2015. Besides data on the bacterial colonization of the two gel particle types (TEP and CSP), we present bacterial densities on different gel particle size classes according to 12 different sampling depths at four sampling locations. Gel particles were frequently abundant at all sampled depths, and their concentrations decreased from the euphotic zone to the dark ocean. They were colonized by bacteria at all sampled water depths with risen importance at the deepest water layers, where fractions of bacteria attached to gel particles (%) increased within the total bacterial community. Due to the omnipresent bacterial colonization of gel particles at all sampled depths in our study, we presume that euphotic production of this type of organic matter may affect microbial species distribution within the whole water column in the Fram Strait, down to the deep sea. Our results raise the question if changes in the bacterial community composition and functioning on gel particles occur over depth, which may affect microbial respiration and remineralization rates of respective particles in different water layers.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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    PAPER (OA)
  • 9
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    Selective feeding in Southern Ocean key grazers—diet composition of krill and salps (2021)
    Springer Nature
    In:  EPIC3Communications Biology, Springer Nature, 4(1), ISSN: 2399-3642
    Details
    Publication Date: 2021-12-15
    Description: Over the past decades, two key grazers in the Southern Ocean (SO), krill and salps, have experienced drastic changes in their distribution and abundance, leading to increasing overlap of their habitats. Both species occupy different ecological niches and long-term shifts in their distributions are expected to have cascading effects on the SO ecosystem. However, studies directly comparing krill and salps are lacking. Here, we provide a direct comparison of the diet and fecal pellet composition of krill and salps using 18S metabarcoding and fatty acid markers. Neither species’ diet reflected the composition of the plankton community, suggesting that in contrast to the accepted paradigm, not only krill but also salps are selective feeders. Moreover, we found that krill and salps had broadly similar diets, potentially enhancing the competition between both species. This could be augmented by salps’ ability to rapidly reproduce in favorable conditions, posing further risks to krill populations.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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  • 10
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    Publisher Correction: Carbon dioxide sink in the Arctic Ocean from cross-shelf transport of dense Barents Sea water (2023)
    Springer Nature
    In:  EPIC3Nature Geoscience, Springer Nature, 16(2), pp. 189-189, ISSN: 1752-0894
    Details
    Publication Date: 2023-08-01
    Description: In the version of this article initially published, author Cora Hörstmann was wrongly listed with a second affiliation with the Department of Ecoscience–Applied Marine Ecology and Modelling, Aarhus University rather than the Mediterranean Institute of Oceanography (MIO), Marseille, France. Furthermore, references 83–97, now found in the Supplementary Tables caption, were wrongly cited in the Data Availability section. The errors have been corrected in the HTML and PDF versions of the article.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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    PAPER (OA)
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