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  • 1
    Electronic Resource
    Electronic Resource
    Isotopic evidence for Mesoarchaean anoxia and changing atmospheric sulphur chemistry (2007)
    [s.l.] : Nature Publishing Group
    Nature 449 (2007), S. 706-709 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The evolution of the Earth’s atmosphere is marked by a transition from an early atmosphere with very low oxygen content to one with an oxygen content within a few per cent of the present atmospheric level. Placing time constraints on this transition is of interest because it identifies ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature06202
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Short-term microbial and physico-chemical variability in low-temperature hydrothermal fluids near 5°S on the Mid-Atlantic Ridge (2009)
    Wiley
    In:  Environmental Microbiology, 11 (10). pp. 2526-2541.
    Details
    Publication Date: 2018-07-18
    Description: This study examines the representativeness of low-temperature hydrothermal fluid samples with respect to their chemical and microbiological characteristics. Within this scope, we investigated short-term temporal chemical and microbial variability of the hydrothermal fluids. For this purpose we collected three fluid samples consecutively from the same spot at the Clueless field near 5 degrees S on the southern Mid-Atlantic Ridge over a period of 50 min. During sampling, the temperature was monitored online. We measured fluid chemical parameters, characterized microbial community compositions and used statistical analyses to determine significant differences between the samples. Overall, the three fluid samples are more closely related to each other than to any other tested habitat. Therefore, on a broad scale, the three collected fluid samples can be regarded as habitat representatives. However, small differences are apparent between all samples. One of the Clueless samples even displayed significant differences (P-value 〈 0.01) to the other two Clueless samples. Our data suggest that the observed variations in fluid chemical and microbial compositions are not reflecting sampling artefacts but are related to short-term fluid variability due to dynamic subseafloor fluid mixing. Recorded temporal changes in fact reflect spatial heterogeneity found in the subsurface as the fluid flows through distinctive pathways. While conservative elements (Cl, Si, Na and K) indicate variable degrees of fluid-seawater mixing, reactive components, including Fe(II), O(2) and H(2)S, show that chemical and microbial reactions within the mixing zone further modify the emanating fluids on short-time scales. Fluids entrain microorganisms, which modify the chemical microenvironment within the subsurface biotopes. This is the first study focusing on short-term microbial variability linked to chemical changes in hydrothermal fluids.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1462-2920.2009.01978.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Microbial CO〈sub〉2〈/sub〉 fixation and sulfur cycling associated with low-temperature emissions at the Lilliput hydrothermal field, southern Mid-Atlantic Ridge (9°S) (2007)
    Society for Applied Microbiology | Blackwell | Wiley
    Details
    Publication Date: 2023-03-22
    Description: Lilliput was discovered in 2005 as the southernmost known hydrothermal field along the Mid-Atlantic Ridge. It is exceptional in that it lacks high-temperature venting probably because of a thickened crust. The absence of thermophilic and hyperthermophilic prokaryotes in emissions supports the argument against the presence of a hot subsurface at Lilliput, as is typically suggested for diffuse emissions from areas of high-temperature venting. The high phylogenetic diversity and novelty of bacteria observed could be because of the low-temperature influence, the distinct location of the hydrothermal field or the Bathymodiolus assemblages covering the sites of discharge. The low-temperature fluids at the Lilliput are characterized by lowered pH and slightly elevated hydrogen (16 nM) and methane (∼2.6 μM) contents compared with ambient seawater. No typical hydrogen and methane oxidizing prokaryotes were detected. The higher diversity of reverse tricarboxylic acid genes and the form II RubisCO genes of the Calvin Benson-Bassham (CBB) cycle compared with the form I RubisCO genes of the CBB cycle suggests that the chemoautotrophic community is better adapted to low oxygen concentrations. Thiomicrospira spp. and Epsilonproteobacteria dominated the autotrophic community. Sulfide is the most abundant inorganic energy source (0.5 mM). Diverse bacteria were associated with sulfur cycling, including Gamma-, Delta- and Epsilonproteobacteria, with the latter being the most abundant bacteria according to fluorescence in situ hybridization. With members of various Candidate Divisions constituting for 25% of clone library sequences we suggest that their role in vent ecosystems might be more important than previously assumed and propose potential mechanisms they might be involved in at the Lilliput hydrothermal field.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Fluid compositions and mineralogy of precipitates from Mid Atlantic Ridge hydrothermal vents at 4°48'S (2009)
    PANGAEA
    Details
    Publication Date: 2024-02-02
    Description: The effect of volcanic activity on submarine hydrothermal systems has been well documented along fast- and intermediate-spreading centers but not from slow-spreading ridges. Indeed, volcanic eruptions are expected to be rare on slow-spreading axes. Here we report the presence of hydrothermal venting associated with extremely fresh lava flows at an elevated, apparently magmatically robust segment center on the slow-spreading southern Mid-Atlantic Ridge near 5°S. Three high-temperature vent fields have been recognized so far over a strike length of less than 2 km with two fields venting phase-separated, vapor-type fluids. Exit temperatures at one of the fields reach up to 407°C, at conditions of the critical point of seawater, the highest temperatures ever recorded from the seafloor. Fluid and vent field characteristics show a large variability between the vent fields, a variation that is not expected within such a limited area. We conclude from mineralogical investigations of hydrothermal precipitates that vent-fluid compositions have evolved recently from relatively oxidizing to more reducing conditions, a shift that could also be related to renewed magmatic activity in the area. Current high exit temperatures, reducing conditions, low silica contents, and high hydrogen contents in the fluids of two vent sites are consistent with a shallow magmatic source, probably related to a young volcanic eruption event nearby, in which basaltic magma is actively crystallizing. This is the first reported evidence for direct magmatic-hydrothermal interaction on a slow-spreading mid-ocean ridge.
    Keywords: DERIDGE; From Mantle to Ocean: Energy-, Material- and Life-cycles at Spreading Axes; M64/1; M64/1-114-ROV; M64/1-123-ROV; M64/1-124-GTV; M64/1-125-ROV; M64/1-130-ROV; M64/1-139-GTV; M64/1-141-ROV; M64/1-146-ROV; M68/1; M68/1-03-ROV; M68/1-07-ROV; M68/1-12-ROV; M68/1-20-ROV; MARSUED2; MARSUED3; Mephisto; Meteor (1986); Mid-Atlantic Ridge at 4-11°S; MULT; Multiple investigations; Remote operated vehicle; ROV; Shrimp_Farm; Sister_Peak; Tannenbaum; Television-Grab; TVG; Two_Boats
    Type: Dataset
    Format: application/zip, 3 datasets
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    DATA PANGAEA
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