GLORIA

GEOMAR Library Ocean Research Information Access

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
Document type
Keywords
Language
  • 1
    In: Marine geology, Amsterdam [u.a.] : Elsevier Science, 1964, (2009), 1872-6151
    In: year:2009
    In: extent:10
    Description / Table of Contents: Porangahau Ridge, located offshore the Wairarapa on the Hikurangi Margin, is an active ocean-continent collision region in northeastern New Zealand coastal waters. Bottom simulating reflections (BSRs) in seismic data indicate the potential for significant gas hydrate deposits across this part of the margin. Beneath Porangahau Ridge a prominent high-amplitude reflection band has been observed to extend from a deep BSR towards the seafloor. Review of the seismic data suggest that this high-amplitude band is caused by local shoaling of the base of gas hydrate stability due to advective heat flow and it may constitute the location of elevated gas hydrate concentrations. During R/V Tangaroa cruise TAN0607 in 2006 heat flow probing for measurements of vertical fluid migration, sediment coring for methane concentrations, and additional seismic profiles were obtained across the ridge. In a subsequent 2007 expedition, on R/V Sonne cruise SO191, a controlled source electromagnetic (CSEM) experiment was conducted along the same seismic, geochemical, and heat flow transect to reveal the electrical resistivity distribution. CSEM data highlight a remarkable coincidence of anomalously high resistivity along the western, landward flank of the ridge which point to locally higher gas hydrate concentration above the high amplitude reflection band. Measured sediment temperature profiles, also along the western flank, consistently show non-linear and concave geothermal gradients typical of advective heat flow. Geochemical data reveal elevated methane concentrations in surface sediments concomitant with a rapid decline in sulfate concentrations indicating elevated methane flux and oxidation of methane in conjunction with sulfate reduction at the landward ridge base. Together, these data sets suggest that the western rim of Porangahau Ridge is a tectonically driven zone of rising fluids that transport methane and cause an upward inflection of the base of gas hydrate stability and the formation of locally enriched gas hydrate above the reflective zone.
    Type of Medium: Online Resource
    Pages: 10 , graph. Darst
    ISSN: 1872-6151
    Language: English
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microcosms may potentially be used as tools for evaluating the fate and effects of genetically engineered microorganisms released into the environment. Extrapolation of data to the field, however, requires that the correspondence between microcosm and field is known. Microbial trophic interactions within the microbial loop were compared quantitatively and qualitatively between field and microcosms containing estuarine water with and without intact sediment cores. The comparison showed that whereas proportions between trophic levels in microcosms were qualitatively similar to those in the field, rates of microbial processes were from 25 to 40% lower in microcosms. Nitrogen cycling was disrupted in microcosms incubated in the dark to eliminate primary production. Examination of the microbial parameters further suggests that sediment in microcosms may be an important factor regulating the bacterial trophic level. These results demonstrate that analysis of microbial trophic interactions is a sensitive method for the field comparison of aquatic microcosms and a potentially useful tool in the risk assessment of genetically engineered microorganisms.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Benzene, toluene, ethylbenzene, and xylene (BTEX) hydrocarbons are typically the most abundant carbon source for bacteria in gasoline-contaminated ground water. In situ bioremediation strategies often involve stimulating bacterial heterotrophic production in an attempt to increase carbon demand of the assemblage. This may, in turn, stimulate biodegradation of contaminant hydrocarbons. In this study, ground water circulation wells (GCWs) were used as an in situ treatment for a fuel-contaminated aquifer to stimulate bacterial production, purportedly by increasing oxygen transfer to the subsurface, circulating limiting nutrients, enhancing bioavailability of hydrocarbons, or by removing metabolically inhibitory volatile organics. Bacterial production, as measured by rates of bacterial protein synthesis, was stimulated across the zone of influence (ZOI) of a series of GCWs. Productivity increased from ∼102 to 〉105 ng C/L hour across the ZOI, suggesting that treatment stimulated overall biodegradation of carbon sources present in the ground water. However, even if BTEX carbon met all bacterial carbon demand, biodegradation would account for 〈4.3% of the total estimated BTEX removed from the ground water. Although bacterial productivity measurements alone cannot prove the effectiveness of in situ bioremediation, they can estimate the maximum amount of contaminant that may be biodegraded by a treatment system.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Natural gas hydrates are a potential source of energy and may play a role in climate change and geological hazards. Most natural gas hydrate appears to be in the form of ‘structure I’, with methane as the trapped guest molecule, although ‘structure II’ hydrate has also ...
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR á€" Recent investigations of the ocean's iron cycle have focused primarily on the response of phytoplankton to iron enrichment1. Bacteria, however, are important in the trophodynamics and elemental cycles of marine ecosystems2'3. With the exception of phototrophic ...
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Stable isotope analysis of bacterial nucleic acids can be used to trace carbon that is assimilated and respired by the bacterioplankton in aquatic ecosystems. However, in sediment and soil environments humic acids co-extract with the nucleic acids, resulting in inaccurate isotope analysis. In this study we have examined the use of amino acids found in bacterial cell walls as biomarkers to trace carbon sources that support growth. In the development of the method, peptidoglycan from laboratory grown Pseudomonas sp. was hydrolyzed to amino acids. Stable carbon isotope ratios (δ13C) were analyzed with a dual mass spectrometer, ion trap and isotope ratio, equipped with a gas chromatograph sample inlet (GC/ITMS/IRMS). Comparisons of δ13C values of whole cells, cell wall peptidoglycan and the amino acids d-alanine and diaminopimelic acid from the cell wall were made using different carbon substrates and through different stages of growth to determine isotopic fractionation of these compounds. The δ13C values of whole cells, peptidoglycan and d-alanine and the substrate sources (glucose, glutamic acid, isoleucine, lysine, phenylalanine) were similar. The δ13C values of the d-alanine were within 0.5‰ of the substrate. In comparison, diaminopimelic acid was enriched in 13C by 10.3‰ relative to the whole cells, peptidoglycan and substrate. Additional laboratory experiments also demonstrated that the δ13C of d-alanine did not vary significantly relative to the whole cell and substrate through different growth stages. Stable carbon isotope analysis of the bacterial amino acids was determined at two field locations, water from Santa Rosa Sound, Florida, a humic rich estuarine ecosystem, and jet-fuel contaminated soils of Tyndall Air Force Base, Florida. d-alanine and diaminopimelic acid were isolated from these water and soil samples and the amino acids were analyzed for purity after extraction and for their δ13C values relative to organic matter in the environments. In the Santa Rosa Sound the δ13C value of d-alanine was −27.6±0.6‰. This value is in the range of δ13C values of bacteria and organic matter previously measured in the system, −24.0 to −27.0‰. The δ13C value of d-alanine in soil samples from Tyndall Air Force Base was −20.5±1.7‰ (n= 4) similar to ranges of values measured for spilled jet-fuel and CO2 respired from the soil at this site. Results from this study demonstrate that d-alanine can be used as a biomarker for analysis of carbon sources that are assimilated by bacteria in soils and sediments.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Microbial ecology 10 (1984), S. 137-149 
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Grazing on planktonic bacteria by microzooplankton was estimated by separating bacteria from the larger plankton with 1μm pore Nuclepore filtration and measuring changes in bacteria in filtered and unfiltered samples over 24 hours. In the absence of grazers, bacteria increased linearly. The regression coefficient of linear increase was used to estimatein situ bacterial production. When grazers were present, the changes in bacteria concentration usually took the form of a linear decline, and grazing was estimated by subtracting the regression coefficient of the unfiltered sample from that of the 1μm filtrate. Results from the Essex estuary-coastal system of northern Massachusetts show grazing and production at rates that indicate a daily turnover of the standing crop of bacteria, with highest values in mid-estuarine waters. Experiments on the size distribution of grazing showed that microzooplankton from 1–3μm were responsible for most of the observed decrease in bacteria. It was suggested that the basic pattern of linear increase of the bacteria in the absence of grazing reflects density-dependent limitation by substrate present at the outset of the incubation and is indicative of a population that has been maintained around the mid-point of the logistic growth curve by grazing.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 353 (1997), S. 53-61 
    ISSN: 1573-5117
    Keywords: bacteria ; heterotrophic microflagellates ; production ; grazing ; carbon ; estuary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bacterial and microflagellate biomass and production and grazing onbacteria were compared weekly at a fixed station in Santa Rosa Sound,Florida, starting in February and ending in October. For bothpopulations the weekly variation in biomass and production was aslarge as the seasonal variation. Cycles for biomass and production ofthese organisms were generally out of phase, rendering it difficultto estimate the net grazing of bacteria by microflagellates atindividual time points. For evaluation of factors that control thefate of carbon cycled by bacterial, experiments were conducted toexamine bacterial growth rates in the absence of predators. Thisexamination resulted in low bacterial growth rates when biomass washigh, and rapid growth rates typically occurred near minimumpopulations. Further analysis suggested that microflagellatepredation was greater than bacterial production during minimumbacterial growth rates. With integration of production and grazingrates over the study period, factors controlling bacterial growthwere examined. Using this approach, 71% of the bacterial productionwas grazed by 〈 8.0µm predators. The microflagellate biomassproduction was 41% of the grazing rate on bacteria. The total amountof bacterial production assimilated into microflagellate biomass was29%. However, based on the variations in biomass and activity of themicrobial assemblages, it appears that substrate and predation exertalternating control on bacterial abundance and production.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 2021-02-08
    Description: The Chatham Rise is located offshore of New Zealand's South Island. Vast areas of the Chatham Rise are covered in circular to elliptical seafloor depressions that appear to be forming through a bathymetrically controlled mechanism, as seafloor depressions 2-5 km in diameter are found in water depths of 800-1100 m. High resolution P-Cable 3D seismic data were acquired in 2013 across one of these depressions. The seafloor depression is interpreted as a mounded contourite. Our data reveal several smaller buried depressions (〈20-650 m diameter) beneath the mounded contourite that we interpret as paleo-pockmarks. These pockmarks are underlain by a complex polygonal fault system that deforms strata and an unusual conical feature. We interpret the conical feature as a sediment remobilization structure based on the presence of stratified reflections within the feature, RMS amplitude values and lack of velocity anomaly that would indicate a non-sedimentary origin. The sediment remobilization structure, polygonal faults and paleo-depressions are indicators of past subsurface fluid flow. We hypothesize that the pockmarks provided the necessary topographic roughness for formation of the mounded contourites thus linking fluid expulsion and deposition of contouritic drifts.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2019-09-23
    Description: Prokaryote communities were investigated on the seasonally stratified Alaska Beaufort Shelf (ABS). Water and sediment directly underlying water with origin in the Arctic, Pacific or Atlantic oceans were analyzed by pyrosequencing and length heterogeneity-PCR in conjunction with physicochemical and geographic distance data to determine what features structure ABS microbiomes. Distinct bacterial communities were evident in all water masses. Alphaproteobacteria explained similarity in Arctic surface water and Pacific derived water. Deltaproteobacteria were abundant in Atlantic origin water and drove similarity among samples. Most archaeal sequences in water were related to unclassified marine Euryarchaeota. Sediment communities influenced by Pacific and Atlantic water were distinct from each other and pelagic communities. Firmicutes and Chloroflexi were abundant in sediment, although their distribution varied in Atlantic and Pacific influenced sites. Thermoprotei dominated archaea in Pacific influenced sediments and Methanomicrobia dominated in methane-containing Atlantic influenced sediments. Length heterogeneity-PCR data from this study were analyzed with data from methane-containing sediments in other regions. Pacific influenced ABS sediments clustered with Pacific sites from New Zealand and Chilean coastal margins. Atlantic influenced ABS sediments formed another distinct cluster. Density and salinity were significant structuring features on pelagic communities. Porosity co-varied with benthic community structure across sites and methane did not. This study indicates that the origin of water overlying sediments shapes benthic communities locally and globally and that hydrography exerts greater influence on microbial community structure than the availability of methane.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...