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  • 1
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    A geochemical model of the Peru Basin deep-sea floor and the response of the system to technical impacts (2001)
    Pergamon Press
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 48 . pp. 3737-3756.
    Details
    Publication Date: 2020-08-05
    Description: A geochemical model of the Peru Basin deep-sea floor, based on an extensive set of field data as well as on numerical simulations, is presented. The model takes into account the vertical oscillations of the redox zonation that occur in response to both long-term (glacial/interglacial) and short-term (El Niño Southern Oscillation (ENSO) time scale) variations in the depositional flux of organic matter. Field evidence of reaction between the pore water NO3− and an oxidizable fraction of the structural Fe(II) in the clay mineral content of the deep-sea sediments is provided. The conditions of formation and destruction of reactive clay Fe(II) layers in the sea floor are defined, whereby a new paleo-redox proxy is established. Transitional NO3− profile shapes are explained by periodic contractions and expansions of the oxic zone (ocean bottom respiration) on the ENSO time scale. The near-surface oscillations of the oxic–suboxic boundary constitute a redox pump mechanism of major importance with respect to diagenetic trace metal enrichments and manganese nodule formation, which may account for the particularly high nodule growth rates in this ocean basin. These conditions are due to the similar depth ranges of both the O2 penetration in the sea floor and the bioturbated high reactivity surface layer (HRSL), all against the background of ENSO-related large variations in depositional Corg flux. Removal of the HRSL in the course of deep-sea mining would result in a massive expansion of the oxic surface layer and, thus, the shut down of the near-surface redox pump for centuries, which is demonstrated by numerical modeling.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0967-0645(01)00065-0
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Unknown
    Persistence of plastic debris and its colonization by bacterial communities after two decades on the abyssal seafloor (2020)
    Nature Research
    Details
    Publication Date: 2023-02-08
    Description: The fate of plastic debris entering the oceans is largely unconstrained. Currently, intensified research is devoted to the abiotic and microbial degradation of plastic floating near the ocean surface for an extended period of time. In contrast, the impacts of environmental conditions in the deep sea on polymer properties and rigidity are virtually unknown. Here, we present unique results of plastic items identified to have been introduced into deep-sea sediments at a water depth of 4150 m in the eastern equatorial Pacific Ocean more than two decades ago. The results, including optical, spectroscopic, physical and microbial analyses, clearly demonstrate that the bulk polymer materials show no apparent sign of physical or chemical degradation. Solely the polymer surface layers showed reduced hydrophobicity, presumably caused by microbial colonization. The bacterial community present on the plastic items differed significantly (p 〈 0.1%) from those of the adjacent natural environment by a dominant presence of groups requiring steep redox gradients (Mesorhizobium, Sulfurimonas) and a remarkable decrease in diversity. The establishment of chemical gradients across the polymer surfaces presumably caused these conditions. Our findings suggest that plastic is stable over extended times under deep-sea conditions and that prolonged deposition of polymer items at the seafloor may induce local oxygen depletion at the sediment-water interface.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
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