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1

Book

Rates and signatures of methane turnover in sediments of continental margins (2005)

Niemann, Helge

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Keywords: Hochschulschrift

Type of Medium: Book

Pages: 265 S , Ill., zahlr. graph. Darst., Kt

DDC: 579.321

Language: English

Note: Auch als elektronisches Dokument vorh , Bremen, Univ., Diss., 2005

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Online Resource

Rates and signatures of methane turnover in sediments of continental margins (2005)

Niemann, Helge

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Keywords: Hochschulschrift

Description / Table of Contents: Continental margin, cold seep, methane, anaerobic oxidation of methane, AOM, sulphate reduction, biogeochemistry, green hous gas, biomarker, archaea, ANME, mud volcano, Haakon Mosby Mud Volcano, Tommeliten, Gulf of Cadiz, pockmark. - In this thesis, a variety of different cold seep systems (mud volcanoes and a gas seep) were investigated using a multidisciplinary approach to gain a more systematic understanding of these, methane-driven biogeosystems. The main goals were the detection and quantification of hot spots of methane oxidation as well as an assessment of environmental factors determining the activity and the distribution of methanotrophic communities. Furthermore, key microbial players were identified and the impact of Anaerobic Oxidation Of Methane (AOM) and Aerobic Oxidation Of Methane (MOx) on the surrounding, marine environment was studied. The investigations revealed the following: 1. Submarine mud volcanoes are colonized by specialized microbial communities utilizing the fluxes of reduced substrates such as methane and sulphide as energy source. At the actively methane-seeping Haakon Mosby mud volcano (HMMV, Barents Sea), a distinct spatial zonation of several novel clades of free-living and symbiotic aerobic and anaerobic methanotrophs was found. The main selection mechanism determining vertical and horizontal distribution and dominance of the methanotrophic communities were fluid flow rates controlling access to electron acceptors for methane oxidation. 2. The analysis of archaeal and bacterial specific lipid ...

Type of Medium: Online Resource

Pages: 265 p. = 5971 KB, text and images

URL: http://nbn-resolving.de/urn:nbn:de:gbv:46-diss000100797

Language: English

Note: Bremen, Univ., Diss., 2005

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3

Electronic Resource

Novel microbial communities of the Haakon Mosby mud volcano and their role as a methane sink (2006)

Niemann, Helge ; Lösekann, Tina ; de Beer, Dirk ; [et al.]

[s.l.] : Nature Publishing Group

Nature 443 (2006), S. 854-858

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ISSN: 1476-4687

Source: Nature Archives 1869 - 2009

Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics

Notes: [Auszug] Mud volcanism is an important natural source of the greenhouse gas methane to the hydrosphere and atmosphere. Recent investigations show that the number of active submarine mud volcanoes might be much higher than anticipated (for example, see refs 3–5), and that gas emitted ...

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1038/nature05227

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4

Electronic Resource

Structural and functional analysis of a microbial mat ecosystem from a unique permanent hypersaline inland lake: ‘La Salada de Chiprana’ (NE Spain) (2003)

Jonkers, Henk M ; Ludwig, Rebecca ; Wit, Rutger ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

FEMS microbiology ecology 44 (2003), S. 0

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ISSN: 1574-6941

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: The benthic microbial mat community of the only permanent hypersaline natural inland lake of Western Europe, ‘La Salada de Chiprana’, northeastern Spain, was structurally and functionally analyzed. The ionic composition of the lake water is characterized by high concentrations of magnesium and sulfate, which were respectively 0.35 and 0.5 M at the time of sampling while the total salinity was 78 g l−1. Community composition was analyzed by microscopy, high-performance liquid chromatography (HPLC) pigment analyses and by studying culturable bacteria from different functional groups. Therefore, denaturing gradient gel electrophoresis (DGGE) was applied on most probable number (MPN) dilution cultures. Microscopy revealed that a thin layer of Chloroflexus-like bacteria overlaid various cyanobacteria-dominated layers each characterized by different morphotypes. DGGE analysis of MPN dilution cultures from distinct mat layers showed that various phylotypes of anoxygenic phototrophic, aerobic heterotrophic, colorless sulfur-, and sulfate-reducing bacteria were present. The mats were furthermore functionally studied and attention was focussed on the relationship between oxygenic primary production and the flow of carbon through the microbial community. Microsensor techniques, porewater and sediment photopigment analysis were applied in order to estimate oxygenic photosynthetic rates, daily dynamics of (in)organic carbon porewater concentration and migration behavior of phototrophs. Chiprana microbial mats produced dissolved organic carbon (DOC) both during the day and night. It was estimated that 14% of the mats gross photosynthetic production and 49% of the mats net photosynthetic production diffused out of the mat in the form of low molecular mass fatty acids, although these compounds made up only 2% of the total DOC pool. The high flux of dissolved fatty acids from the microbial mat to the water column may explain why in this system Chloroflexus-like bacteria proliferate on top of the cyanobacterial layers since these photoheterotrophic bacteria grow preferably on organic phototrophic exudates. Furthermore it may also explain why high numbers of viable sulfate-reducing bacteria were found in the fully oxygenated sediment surface layers. These organisms apparently do not have to compete with aerobic heterotrophic community members due to the ample availability of organic substrates. Moreover, the high production of DOC strongly indicates that the mat community was nutrient limited in its growth. Photopigment analysis revealed furthermore that chlorophyll a (Chla) and three of its allomeres had a complementary depth distribution what suggests that the Chla allomeres are functional adaptations to differences in light quality and/or quantity and may be species specific.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1016/S0168-6496(02)00464-6

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Life on the edge: active microbial communities in the Kryos MgCl2-brine basin at very low water activity (2018)

Steinle, Lea ; Knittel, Katrin ; Felber, Nicole ; [et al.]

Nature Research

In: The ISME Journal, 12 (6). pp. 1414-1426.

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Publication Date: 2021-02-08

Description: The Kryos Basin is a deep-sea hypersaline anoxic basin (DHAB) located in the Eastern Mediterranean Sea (34.98°N 22.04°E). It is filled with brine of re-dissolved Messinian evaporites and is nearly saturated with MgCl2-equivalents, which makes this habitat extremely challenging for life. The strong density difference between the anoxic brine and the overlying oxic Mediterranean seawater impedes mixing, giving rise to a narrow chemocline. Here, we investigate the microbial community structure and activities across the seawater–brine interface using a combined biogeochemical, next-generation sequencing, and lipid biomarker approach. Within the interface, we detected fatty acids that were distinctly 13C-enriched when compared to other fatty acids. These likely originated from sulfide-oxidizing bacteria that fix carbon via the reverse tricarboxylic acid cycle. In the lower part of the interface, we also measured elevated rates of methane oxidation, probably mediated by aerobic methanotrophs under micro-oxic conditions. Sulfate reduction rates increased across the interface and were highest within the brine, providing first evidence that sulfate reducers (likely Desulfovermiculus and Desulfobacula) thrive in the Kryos Basin at a water activity of only ~0.4 Aw. Our results demonstrate that a highly specialized microbial community in the Kryos Basin has adapted to the poly-extreme conditions of a DHAB with nearly saturated MgCl2 brine, extending the known environmental range where microbial life can persist.

Type: Article , PeerReviewed

Format: text

DOI: 10.1038/s41396-018-0107-z

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Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard (2015)

Graves, Carolyn A. ; Steinle, Lea ; Rehder, Gregor ; [et al.]

AGU (American Geophysical Union) | Wiley

In: Journal of Geophysical Research: Oceans, 120 (9). pp. 6185-6201.

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Publication Date: 2017-05-02

Description: Widespread seepage of methane from seafloor sediments offshore Svalbard close to the landward limit of the gas hydrate stability zone (GHSZ) may, in part, be driven by hydrate destabilization due to bottom water warming. To assess whether this methane reaches the atmosphere where it may contribute to further warming, we have undertaken comprehensive surveys of methane in seawater and air on the upper slope and shelf region. Near the GHSZ limit at ∼400 m water depth, methane concentrations are highest close to the seabed, reaching 825 nM. A simple box model of dissolved methane removal from bottom waters by horizontal and vertical mixing and microbially mediated oxidation indicates that ∼60% of methane released at the seafloor is oxidized at depth before it mixes with overlying surface waters. Deep waters are therefore not a significant source of methane to intermediate and surface waters; rather, relatively high methane concentrations in these waters (up to 50 nM) are attributed to isopycnal turbulent mixing with shelf waters. On the shelf, extensive seafloor seepage at 〈100 m water depth produces methane concentrations of up to 615 nM. The diffusive flux of methane from sea to air in the vicinity of the landward limit of the GHSZ is ∼4-20 μmol m-2 d-1, which is small relative to other Arctic sources. In support of this, analyses of mole fractions and the carbon isotope signature of atmospheric methane above the seeps do not indicate a significant local contribution from the seafloor source.

Type: Article , PeerReviewed

Format: text

DOI: 10.1002/2015JC011084

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Effects of climate change on methane emissions from seafloor sediments in the Arctic Ocean: A review (2016)

James, Rachael H. ; Bousquet, Philippe ; Bussmann, Ingeborg ; [et al.]

ASLO (Association for the Sciences of Limnology and Oceanography)

In: Limnology and Oceanography, 61 (S1). pp. 301-309.

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Publication Date: 2019-09-24

Description: Large quantities of methane are stored in hydrates and permafrost within shallow marine sediments in the Arctic Ocean. These reservoirs are highly sensitive to climate warming, but the fate of methane released from sediments is uncertain. Here, we review the principal physical and biogeochemical processes that regulate methane fluxes across the seabed, the fate of this methane in the water column, and potential for its release to the atmosphere. We find that, at present, fluxes of dissolved methane are significantly moderated by anaerobic and aerobic oxidation of methane. If methane fluxes increase then a greater proportion of methane will be transported by advection or in the gas phase, which reduces the efficiency of the methanotrophic sink. Higher freshwater discharge to Arctic shelf seas may increase stratification and inhibit transfer of methane gas to surface waters, although there is some evidence that increased stratification may lead to warming of sub-pycnocline waters, increasing the potential for hydrate dissociation. Loss of sea-ice is likely to increase wind speeds and seaair exchange of methane will consequently increase. Studies of the distribution and cycling of methane beneath and within sea ice are limited, but it seems likely that the sea-air methane flux is higher during melting in seasonally ice-covered regions. Our review reveals that increased observations around especially the anaerobic and aerobic oxidation of methane, bubble transport, and the effects of ice cover, are required to fully understand the linkages and feedback pathways between climate warming and release of methane from marine sediments.

Type: Article , PeerReviewed , info:eu-repo/semantics/article

Format: text

DOI: 10.1002/lno.10307

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Effects of low oxygen concentrations on aerobic methane oxidation in seasonally hypoxic coastal waters (2017)

Steinle, Lea ; Maltby, Johanna ; Treude, Tina ; [et al.]

Copernicus Publications (EGU)

In: Biogeosciences (BG), 14 (6). pp. 1631-1645.

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Publication Date: 2020-10-26

Description: Coastal seas may account for more than 75 % of global oceanic methane emissions. There, methane is mainly produced microbially in anoxic sediments from where it can escape to the overlying water column. Aerobic methane oxidation (MOx) in the water column acts as a biological filter reducing the amount of methane that eventually evades to the atmosphere. The efficiency of the MOx filter is potentially controlled by the availability of dissolved methane and oxygen, as well as temperature, salinity, and hydrographic dynamics, and all of these factors undergo strong temporal fluctuations in coastal ecosystems. In order to elucidate the key environmental controls, specifically the effect of oxygen availability, on MOx in a seasonally stratified and hypoxic coastal marine setting, we conducted a 2-year time-series study with measurements of MOx and physico-chemical water column parameters in a coastal inlet in the southwestern Baltic Sea (Eckernförde Bay). We found that MOx rates always increased toward the seafloor, but were not directly linked to methane concentrations. MOx exhibited a strong seasonal variability, with maximum rates (up to 11.6 nmol l−1 d−1) during summer stratification when oxygen concentrations were lowest and bottom-water temperatures were highest. Under these conditions, 70–95 % of the sediment-released methane was oxidized, whereas only 40–60 % were consumed during the mixed and oxygenated periods. Laboratory experiments with manipulated oxygen concentrations in the range of 0.2–220 µmol l−1 revealed a sub-micromolar oxygen-optimum for MOx at the study site. In contrast, the fraction of methane-carbon incorporation into the bacterial biomass (compared to the total amount of oxidised methane) was up to 38-fold higher at saturated oxygen concentrations, suggesting a different partitioning of catabolic and anabolic processes under oxygen-replete and oxygen-starved conditions, respectively. Our results underscore the importance of MOx in mitigating methane emission from coastal waters and indicate an organism-level adaptation of the water column methanotrophs to hypoxic conditions.

Type: Article , PeerReviewed

Format: text

DOI: 10.5194/bg-14-1631-2017

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