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  • 1
    Online-Ressource
    Online-Ressource
    American Association for the Advancement of Science (AAAS) ; 2017
    In:  Science Advances Vol. 3, No. 3 ( 2017-03-03)
    In: Science Advances, American Association for the Advancement of Science (AAAS), Vol. 3, No. 3 ( 2017-03-03)
    Kurzfassung: Purely inorganic reactions of silica, metal carbonates, and metal hydroxides can produce self-organized complex structures that mimic the texture of biominerals, the morphology of primitive organisms, and that catalyze prebiotic reactions. To date, these fascinating structures have only been synthesized using model solutions. We report that mineral self-assembly can be also obtained from natural alkaline silica-rich water deriving from serpentinization. Specifically, we demonstrate three main types of mineral self-assembly: (i) nanocrystalline biomorphs of barium carbonate and silica, (ii) mesocrystals and crystal aggregates of calcium carbonate with complex biomimetic textures, and (iii) osmosis-driven metal silicate hydrate membranes that form compartmentalized, hollow structures. Our results suggest that silica-induced mineral self-assembly could have been a common phenomenon in alkaline environments of early Earth and Earth-like planets.
    Materialart: Online-Ressource
    ISSN: 2375-2548
    Sprache: Englisch
    Verlag: American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 2017
    ZDB Id: 2810933-8
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 9 ( 2022-10-20)
    Kurzfassung: Cold-water corals mounds develop over millennial timescales as a result of sustained coral growth and concurrent with sediment deposition within their coral frameworks. So far, coral mounds have been primarily investigated as deep-sea biodiversity hotspots and geo-biological paleo-archives, whereas their morphological appearance and spatial arrangement have received much less attention. Here, we analysed the spatial distribution and the morphometry of coral mounds that developed on the Namibian shelf during a single short period dating back to the Early. The spatial distribution of these “early-stage” mounds and their morphological characteristics revealed a hierarchy of three different patterns. These comprise an alongslope mound distribution at a regional scale ( first-order pattern), a topography-steered downslope alignment of mounds at a local scale ( second-order pattern), and a hydrodynamic-controlled downslope orientation of the individual mounds at a mound scale ( third-order pattern). In addition, because the Namibian mounds rarely exceed 20 m in height, key steps in the development of early-stage coral mounds (e.g. elongation, merging, limited gain in height compared to lateral extension) have been identified. With increasing size, coral mounds are more elongated, parallel to the prevailing tidal system, which is interpreted to reflect the transition from an “inherited” to a “developed” mound morphology. Besides supporting this earlier hypothesis on mound development, we could show that this transition takes place when the Namibian coral mounds reach ~150 m in length and ~8 m in height. This study reveals that the spatial-morphological appearance of coral mounds, often treated as a descriptive information, can provide valid information to understand their formation.
    Materialart: Online-Ressource
    ISSN: 2296-7745
    Sprache: Unbekannt
    Verlag: Frontiers Media SA
    Publikationsdatum: 2022
    ZDB Id: 2757748-X
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Online-Ressource
    Online-Ressource
    Informa UK Limited ; 2018
    In:  Archives of Environmental & Occupational Health Vol. 73, No. 5 ( 2018-09-03), p. 270-277
    In: Archives of Environmental & Occupational Health, Informa UK Limited, Vol. 73, No. 5 ( 2018-09-03), p. 270-277
    Materialart: Online-Ressource
    ISSN: 1933-8244 , 2154-4700
    Sprache: Englisch
    Verlag: Informa UK Limited
    Publikationsdatum: 2018
    ZDB Id: 2245971-6
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    In: Geology, Geological Society of America, Vol. 47, No. 12 ( 2019-12-01), p. 1185-1188
    Kurzfassung: An exceptionally large cold-water coral mound province (CMP) was recently discovered extending over 80 km along the Namibian shelf (offshore southwestern Africa) in water depths of 160–270 m. This hitherto unknown CMP comprises 〉 2000 mounds with heights of up to 20 m and constitutes the largest CMP known from the southeastern Atlantic Ocean. Uranium-series dating revealed a short but intense pulse in mound formation during the early to mid-Holocene. Coral proliferation during this period was potentially supported by slightly enhanced dissolved oxygen concentrations compared to the present Benguela oxygen minimum zone (OMZ). The subsequent mid-Holocene strengthening of the Benguela Upwelling System and a simultaneous northward migration of the Angola-Benguela Front resulted in an intensification of the OMZ that caused the sudden local extinction of the Namibian corals and prevented their reoccurrence until today.
    Materialart: Online-Ressource
    ISSN: 0091-7613 , 1943-2682
    Sprache: Englisch
    Verlag: Geological Society of America
    Publikationsdatum: 2019
    ZDB Id: 184929-3
    ZDB Id: 2041152-2
    SSG: 13
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    In: Marine and Petroleum Geology, Elsevier BV, Vol. 107 ( 2019-09), p. 20-31
    Materialart: Online-Ressource
    ISSN: 0264-8172
    Sprache: Englisch
    Verlag: Elsevier BV
    Publikationsdatum: 2019
    ZDB Id: 1494910-6
    ZDB Id: 48427-1
    SSG: 13
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    In: Biogeosciences, Copernicus GmbH, Vol. 16, No. 22 ( 2019-11-15), p. 4337-4356
    Kurzfassung: Abstract. Thriving benthic communities were observed in the oxygen minimum zones along the southwestern African margin. On the Namibian margin, fossil cold-water coral mounds were overgrown by sponges and bryozoans, while the Angolan margin was characterized by cold-water coral mounds covered by a living coral reef. To explore why benthic communities differ in both areas, present-day environmental conditions were assessed, using conductivity–temperature–depth (CTD) transects and bottom landers to investigate spatial and temporal variations of environmental properties. Near-bottom measurements recorded low dissolved oxygen concentrations on the Namibian margin of 0–0.15 mL L−1 (≜0 %–9 % saturation) and on the Angolan margin of 0.5–1.5 mL L−1 (≜7 %–18 % saturation), which were associated with relatively high temperatures (11.8–13.2 ∘C and 6.4–12.6 ∘C, respectively). Semidiurnal barotropic tides were found to interact with the margin topography producing internal waves. These tidal movements deliver water with more suitable characteristics to the benthic communities from below and above the zone of low oxygen. Concurrently, the delivery of a high quantity and quality of organic matter was observed, being an important food source for the benthic fauna. On the Namibian margin, organic matter originated directly from the surface productive zone, whereas on the Angolan margin the geochemical signature of organic matter suggested an additional mechanism of food supply. A nepheloid layer observed above the cold-water corals may constitute a reservoir of organic matter, facilitating a constant supply of food particles by tidal mixing. Our data suggest that the benthic fauna on the Namibian margin, as well as the cold-water coral communities on the Angolan margin, may compensate for unfavorable conditions of low oxygen levels and high temperatures with enhanced availability of food, while anoxic conditions on the Namibian margin are at present a limiting factor for cold-water coral growth. This study provides an example of how benthic ecosystems cope with such extreme environmental conditions since it is expected that oxygen minimum zones will expand in the future due to anthropogenic activities.
    Materialart: Online-Ressource
    ISSN: 1726-4189
    Sprache: Englisch
    Verlag: Copernicus GmbH
    Publikationsdatum: 2019
    ZDB Id: 2158181-2
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    Online-Ressource
    Online-Ressource
    Springer Science and Business Media LLC ; 2021
    In:  Scientific Reports Vol. 11, No. 1 ( 2021-07-26)
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 11, No. 1 ( 2021-07-26)
    Kurzfassung: This study aims to map the occurrence and distribution of Madrepora oculata and to quantify density and colony sizes across recently discovered coral mounds off Angola. Despite the fact that the Angolan populations of M. oculata thrive under extreme hypoxic conditions within the local oxygen minimum zone, they reveal colonies with remarkable heights of up to 1250 mm—which are the tallest colonies ever recorded for this species—and average densities of 0.53 ± 0.37 (SD) colonies m −2 . This is particularly noteworthy as these values are comparable to those documented in areas without any oxygen constraints. The results of this study show that the distribution pattern documented for M. oculata appear to be linked to the specific regional environmental conditions off Angola, which have been recorded in the direct vicinity of the thriving coral community. Additionally, an estimated average colony age of 95 ± 76 (SD) years (total estimated age range: 16–369 years) indicates relatively old M. oculata populations colonizing the Angolan coral mounds. Finally, the characteristics of the Angolan populations are benchmarked and discussed in the light of the existing knowledge on M. oculata gained from the North Atlantic and Mediterranean Sea.
    Materialart: Online-Ressource
    ISSN: 2045-2322
    Sprache: Englisch
    Verlag: Springer Science and Business Media LLC
    Publikationsdatum: 2021
    ZDB Id: 2615211-3
    Standort Signatur Einschränkungen Verfügbarkeit
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