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  • 1
    E-Resource
    E-Resource
    Structure and drivers of cold seep ecosystems (2009)
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    In: Oceanography, Rockville, MD : The Oceanography Society, 1988, 22(2009), 1, Seite 92-109, 2377-617X
    In: volume:22
    In: year:2009
    In: number:1
    In: pages:92-109
    Description / Table of Contents: Submarine hydrocarbon seeps are geologically driven "hotspots" of increased biological activity on the seabed. As part of the HERMES project, several sites of natural hydrocarbon seepage in the European seas were investigated in detail, including mud volcanoes and pockmarks, in study areas extending from the Nordic margin, to the Gulf of Cádiz, to the Mediterranean and Black seas. High-resolution seabed maps and the main properties of key seep sites are presented here. Individual seeps show ecosystem zonation related to the strength of the methane flux and distinct biogeochemical processes in surface sediments. A feature common to many seeps is the formation of authigenic carbonate constructions. These constructions exhibit various morphologies ranging from large pavements and fragmented slabs to chimneys and mushroom-shaped mounds, and they form hard substrates colonized by fixed fauna. Gas hydrate dissociation could contribute to sustain seep chemosynthetic communities over several thousand years following large gas-release events.
    Type of Medium: Electronic Resource
    Pages: Ill., graph. Darst
    ISSN: 2377-617X
    Language: English
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  • 2
    Electronic Resource
    Electronic Resource
    Digestive enzymes in marine invertebrates from hydrothermal vents and other reducing environments (1995)
    Springer
    Marine biology 122 (1995), S. 105-113 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The present study demonstrates the potential hydrolytic activities in the symbiont-containing tissues of the vent invertebrates Riftia pachyptila, Bathymodiolus thermophilus (collected in 1991 at the East Pacific Rise) and the shallow-water bivalve Lucinoma aequizonata (collected in 1991 from the Santa Barbara Basin). Activities of phosphatases, esterases, β-glucuronidase and leucineaminopeptidase were comparable to those of digestive tract tissues of other marine invertebrates. A lack in most glycosidases as well as in trypsin and chymotrypsin was observed. Activities of lysozyme and chitobiase were rather high. In all vent invertebrates with symbionts and in L. aequizonata, the symbiont-containing tissues and the symbiont-free tissues had similar levels of enzymatic activities, indicating that polymeric nutrients could be hydrolysed after release from the symbionts and cellular uptake. The high activities of α-fucosidase in all vent invertebrates as well as in the shallow-water bivalve L. aequizonata could point to the existence of a yet undescribed substrate available to hydrolysation. The ectosymbionts-carrying polychaete Alvinella pompejana (collected in 1991 at the East Pacific Rise, EPR) shows high lysozyme activities in its gut, consistent with the proposed food source of bacteria. For the vent crab Bythogrea thermydron (also collected in 1991 at the EPR) hydrolytic activities were highest in the gut, dominated by esterase and peptidase activities which support their proposed carnivorous food source. A snail and a limpet collected from R. pachyptila tubes showed high levels of chitobiase suggesting a food source of grazed bacteria or ingested R. pachyptila tube.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349283
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    In situ experimental evidence of the fate of a phytodetritus pulse at the abyssal sea floor (2003)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 424 (2003), S. 763-766 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] More than 50% of the Earth' s surface is sea floor below 3,000 m of water. Most of this major reservoir in the global carbon cycle and final repository for anthropogenic wastes is characterized by severe food limitation. Phytodetritus is the major food source for abyssal benthic ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature01799
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Microbial hydrolytic enzyme activities in deep-sea sediments (1995)
    Springer
    Helgoland marine research 49 (1995), S. 177-187 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The potential hydrolysis rates of five different hydrolytic enzymes were determined in deep-sea sediments from the northeast Atlantic (BIOTRANS area) in March 1992. Fluorogenic substrates were used to assay extracellular α- and β-glucosidase, chitobiase, lipase and aminopeptidase. The potential activity of most of the enzymes investigated decreased to a minimum within the upper two centimetre range, whereas aminopeptidase was high over the upper five centimetre range. Exceptions were found when macrofaunal burrows occurred in the cores, always increasing the activities of some hydrolases, and therefore indicating the impact of bioturbation on degradation rates. The most striking feature of the investigated enzyme spectrum was the 50–2000 times higher specific activity of the aminopeptidase, compared with the other hydrolases. The activity of hydrolytic enzymes most likely reflects the availability of their respective substrates and is not a function of bacterial biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02368348
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  • 5
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    Effects of fluctuating hypoxia on benthic oxygen consumption in the Black Sea (Crimean shelf) (2015)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 12 (16). pp. 5075-5092.
    Details
    Publication Date: 2017-05-09
    Description: The outer western Crimean shelf of the Black Sea is a natural laboratory to investigate effects of stable oxic versus varying hypoxic conditions on seafloor biogeochemical processes and benthic community structure. Bottom-water oxygen concentrations ranged from normoxic (175 μmol O2 L−1) and hypoxic (〈 63 μmol O2 L−1) or even anoxic/sulfidic conditions within a few kilometers' distance. Variations in oxygen concentrations between 160 and 10 μmol L−1 even occurred within hours close to the chemocline at 134 m water depth. Total oxygen uptake, including diffusive as well as fauna-mediated oxygen consumption, decreased from 15 mmol m−2 d−1 on average in the oxic zone, to 7 mmol m−2 d−1 on average in the hypoxic zone, correlating with changes in macrobenthos composition. Benthic diffusive oxygen uptake rates, comprising respiration of microorganisms and small meiofauna, were similar in oxic and hypoxic zones (on average 4.5 mmol m−2 d−1), but declined to 1.3 mmol m−2 d−1 in bottom waters with oxygen concentrations below 20 μmol L−1. Measurements and modeling of porewater profiles indicated that reoxidation of reduced compounds played only a minor role in diffusive oxygen uptake under the different oxygen conditions, leaving the major fraction to aerobic degradation of organic carbon. Remineralization efficiency decreased from nearly 100 % in the oxic zone, to 50 % in the oxic–hypoxic zone, to 10 % in the hypoxic–anoxic zone. Overall, the faunal remineralization rate was more important, but also more influenced by fluctuating oxygen concentrations, than microbial and geochemical oxidation processes.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/bg-12-5075-2015
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    An experimental study on short-term changes in the anaerobic oxidation of methane in response to varying methane and sulfate fluxes (2009)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 6 . pp. 867-876.
    Details
    Publication Date: 2017-08-08
    Description: A major role in regulation of global methane fluxes has been attributed to the process of anaerobic oxidation of methane (AOM), which is performed by consortia of methanotrophic archaea and sulfate reducing bacteria. An important question remains how these energy limited, slow growing Microorganisms with generation times of 3–7 months respond to rapid natural variations in methane fluxes at cold seeps. We used an experimental flow-through column system filled with cold seep sediments naturally enriched in methanotrophic communities, to test their responses to short-term variations in methane and sulfate fluxes. At stable methane and sulfate concentrations of ∼2 mM and 28 mM, respectively, we measured constant rates of AOM and sulfate reduction (SR) for up to 160 days of incubation. When percolated with methane-free medium, the anaerobic methanotrophs ceased to produce sulfide. After a starvation phase of 40 days, the addition of methane restored former AOM and SR rates immediately. At methane concentrations between 0–2.3 mM we measured a linear correlation between methane availability, AOM and SR. At constant fluid flow velocities of 30 m yr−1, ca. 50% of the methane was consumed by the anaerobic methanotrophic (ANME) population at all concentrations tested. Reducing the sulfate concentration from 28 to 1 mM, a decrease in AOM and SR by 50% was observed, and 45% of the methane was consumed. Hence, the marine anaerobic methanotrophs(ANME) are capable of oxidizing substantial amounts of methane over a wide and variable range of fluxes of the reaction educts.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/bg-6-867-2009
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Subsurface Microbial Methanotrophic Mats in the Black Sea (2005)
    American Society for Microbiology
    In:  Applied and Environmental Microbiology, 71 (10). pp. 6375-6378.
    Details
    Publication Date: 2017-06-28
    Description: A nodule-shaped microbial mat was found subsurface in sediments of a gas seep in the anoxic Black Sea. This mat was dominated by ANME-1 archaea and consumed methane and sulfate simultaneously. We propose that such subsurface mats represent the initial stage of previously investigated microbial reefs.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1128/AEM.71.10.6375-6378.2005
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Microbial Reefs in the Black Sea Fueled by Anaerobic Oxidation of Methane (2002)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 297 (5583). pp. 1013-1015.
    Details
    Publication Date: 2017-07-07
    Description: Massive microbial mats covering up to 4-meter-high carbonate buildups prosper at methane seeps in anoxic waters of the northwestern Black Sea shelf. Strong 13C depletions indicate an incorporation of methane carbon into carbonates, bulk biomass, and specific lipids. The mats mainly consist of densely aggregated archaea (phylogenetic ANME-1 cluster) and sulfate-reducing bacteria (Desulfosarcina/Desulfococcusgroup). If incubated in vitro, these mats perform anaerobic oxidation of methane coupled to sulfate reduction. Obviously, anaerobic microbial consortia can generate both carbonate precipitation and substantial biomass accumulation, which has implications for our understanding of carbon cycling during earlier periods of Earth's history.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1126/science.1072502
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    PNAS Plus: Carbon and sulfur back flux during anaerobic microbial oxidation of methane and coupled sulfate reduction (2011)
    National Academy of Sciences
    In:  PNAS Proceedings of the National Academy of Sciences of the United States of America, 108 (52). E1484-E1490.
    Details
    Publication Date: 2016-10-25
    Description: Microbial degradation of substrates to terminal products is commonly understood as a unidirectional process. In individual enzymatic reactions, however, reversibility (reverse reaction and product back flux) is common. Hence, it is possible that entire pathways of microbial degradation are associated with back flux from the accumulating product pool through intracellular intermediates into the substrate pool. We investigated carbon and sulfur back flux during the anaerobic oxidation of methane (AOM) with sulfate, one of the least exergonic microbial catabolic processes known. The involved enzymes must operate not far from the thermodynamic equilibrium. Such an energetic situation is likely to favor product back flux. Indeed, cultures of highly enriched archaeal–bacterial consortia, performing net AOM with unlabeled methane and sulfate, converted label from 14C-bicarbonate and 35S-sulfide to 14C-methane and 35S-sulfate, respectively. Back fluxes reached 5% and 13%, respectively, of the net AOM rate. The existence of catabolic back fluxes in the reverse direction of net reactions has implications for biogeochemical isotope studies. In environments where biochemical processes are close to thermodynamic equilibrium, measured fluxes of labeled substrates to products are not equal to microbial net rates. Detection of a reaction in situ by labeling may not even indicate a net reaction occurring in the direction of label conversion but may reflect the reverse component of a so far unrecognized net reaction. Furthermore, the natural isotopic composition of the substrate and product pool will be determined by both the forward and back flux. This finding may have to be considered in the interpretation of stable isotope records.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1073/pnas.1106032108
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Export of Algal Biomass from the Melting Arctic Sea Ice (2013)
    American Association for the Advancement of Science (AAAS)
    In:  Science, 339 (6126). pp. 1430-1432.
    Details
    Publication Date: 2014-09-04
    Description: In the Arctic, under-ice primary production is limited to summer months and is restricted not only by ice thickness and snow cover but also by the stratification of the water column, which constrains nutrient supply for algal growth. Research Vessel Polarstern visited the ice-covered eastern-central basins between 82° to 89°N and 30° to 130°E in summer 2012, when Arctic sea ice declined to a record minimum. During this cruise, we observed a widespread deposition of ice algal biomass of on average 9 grams of carbon per square meter to the deep-sea floor of the central Arctic basins. Data from this cruise will contribute to assessing the effect of current climate change on Arctic productivity, biodiversity, and ecological function.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1126/science.1231346
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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