Science.gov

Sample records for mexico hydrocarbon seep

  1. Methanotrophic gastropods from a bathyal hydrocarbon seep, Gulf of Mexico

    SciTech Connect

    Anderson, L.C.; Aharon, P.; Gupta, S. )

    1992-01-01

    Two gastropods, Neritina sp. and Truncatella sp., collected live from a Gulf of Mexico active gas seep with the submersible Johnson Sea Link in September 1991, apparently incorporate methane-derived carbon in their soft tissues. Flesh of an individual Neritina sp. had a delta C-13 of [minus]50.92 per mil PDB, and that of two coexisting individuals of Truncatella sp. had values of [minus]45.11 and [minus]49.27 per mil. These isotope values are comparable to those reported for the methanotrophic mytilid bivalve Bathymodiolus sp. from other hydrocarbon seeps on the Gulf of Mexico, and are lighter than published isotopic values of chemosynthetic organisms with sulfur-oxidizing symbionts. The anomalously light carbon-isotopic values of Neritina sp. and Truncatella sp. may steam from one of three causes: (1) these gastropods host symbiotic methanotrophic bacteria, (2) their chief food is methane-oxidizing bacteria present at the seep, or (3) they incorporate some carbon from the periostracum of mussels on which they may graze. The presence of abundant juveniles of Bathymodiolus, reported to settle preferentially in areas of active seepage and high methane release, indicates that methane was abundant and supported a community with multiple trophic levels. Generally, studies of hydrocarbon-seep communities have focused on larger community members, especially bivalves and tube worms. The presence of living Neritina and Truncatella at the authors sampling site, however, draws attention to the fact that these gastropods are integral and significant parts of hydrocarbon-seep communities. Both gastropod species are members of genera that characteristically inhabit shallow marine, intertidal, and semiterrestrial environments. The presence of these genera in bathyal hydrocarbon seeps indicates that they have very broad environmental ranges, thus limiting their utility in paleoecologic reconstructions.

  2. Important geological and biological impacts of natural hydrocarbon seeps: Northern Gulf of Mexico continental slope

    SciTech Connect

    Roberts, H.H. )

    1993-11-01

    Large volumes of siliciclastic sediments, input especially during periods of lowered sea level, and compensating salt tectonics have produced a continental slope that is arguably the most complex in today's oceans. Faults associated with deformation of salt and shale provide the primary migration routes for hydrocarbon gases, crude oil, brines, and formation fluids to the modern sea floor. Since the mid 1980s, it has become increasingly clearer that this process has an extremely important impact on the geomorphology, sedimentology, and biology of the modern continental slope. Hydrocarbon source, flux rate, and water depth are important determinants of sea-floor response. Under rapid flux conditions mud volcanoes (to 1 km wide and 50 m high) result, and hydrate hills (rich with authigenic carbonates), carbonate lithoherms, and isolated communities of chemosymbiotic organisms with associated hardgrounds represent much slower flux responses. In numerous moderate- to low-flux cases, cold seep products function to support islands of productivity for communities of chemosymbiotic organisms that contribute both directly (shell material) and through chemical byproducts to the production of massive volumes of calcium-magnesium carbonate in the form of hardgrounds, stacked slabs, and discrete moundlike buildups (commonly >20m). Seep-related carbonates of the Gulf of Mexico continental slope, as well those formed through degassing of accretionary prisms along active margins, are now thought to create hardgrounds and discrete buildups that are excellent analogs for many problematic carbonate buildups in ancient deep-water siliciclastic rocks.

  3. Nutritional associations among fauna at hydrocarbon seep communities in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Macavoy, S. E.; Fisher, C. R.; Carney, R. S.; Macko, S. A.

    2004-05-01

    The Gulf of Mexico supports dense aggregations of megafauna associated with hydrocarbon seeps on the Louisiana Slope. The visually dominant megafauna at the seeps, mussels and tubeworms, derive their nutrition from symbiotic relationships with sulfide or methane oxidizing bacteria. The structure of the tubeworm aggregations provide biogenic habitat for numerous other species of heterotrophic animals. Carbon, nitrogen and sulfur stable isotope analyses of heterotrophic fauna collected with tubeworm aggregations in the Green Canyon Lease area (GC 185) indicate that most of these species derive the bulk of their nutrition from chemoautotrophic sources. The isotope analyses also indicates that although two species may be deriving significant nutritional input from the bivalves, none of the species analyzed are feeding directly on the tubeworms. Grazing gastropods and deposit feeding sipuncluids were used to estimate the isotopic value of the free-living chemoautotrophic bacteria associated with the tubeworms (d13C -32 to -20%; d15N 0 to 7%; d34S -14 to -1 %). The use of tissue d34S analyses in conjunction with tissue d13C and d15N led to several insights into the trophic biology of the communities that would not have been evident from tissue stable C and N analyses alone.

  4. Exploration and Discovery of Hydrocarbon Seeps, Coral Ecosystems, and Shipwrecks in the Deep Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Shank, T. M.; Hsing, P.; Carney, R. S.; Herrera, S.; Heyl, T.; Munro, C.; Bors, E.; Kiene, W.; Vecchione, M.; Evans, A.; Irion, J.; Warren, D.; Malik, M.; Lobecker, M.; Potter, J.

    2012-12-01

    Between March 20 and April 6, 2012, the NOAA Ship Okeanos Explorer served as a platform for ship-board and shore-side scientists to explore the deep Gulf of Mexico, targeting the northern West Florida Escarpment, DeSoto Canyon, the vicinity (within 11km) of the Deepwater Horizon (DWH) well, and deepwater shipwrecks. We systematically explored and discovered natural hydrocarbon seeps, diverse coral ecosystems, wooden and iron-hulled shipwrecks more than 100 years old colonized by coral communities, and sperm whale habitat between 600 and 1200m. A total of sixteen dives took advantage of new and recent maps to explore and groundtruth both hard and soft-bottom habitats, from cretaceous carbonates to mounds of coral rubble. The final ROV dive successfully groundtruthed expected methane-release areas imaged by the ship's mapping systems up to 1150m above the seafloor. The source of the mapping imagery was a stream of bubbles issuing from beneath thriving seep mussel communities. We visited five sites in the Mississippi Canyon (MC) area (lease blocks MC294, MC297, MC388, MC255, and MC036; the DWH incident took place in MC252). These sites were 11.3 km SW, 6.8 km SW, 7.6 km SW, 25.7 km E, and 27.4 km to the NE of the DWH, respectively. We used high-definition imaging systems on the Little Hercules ROV and Seirios camera platform to document more than 130 coral colonies and over 400 associated individual animals to continue to assessing the impact of the Deepwater Horizon oil spill. All of these efforts were conducted to provide fundamental knowledge of unknown and poorly known regions, ecosystems, and items of historical significance in the deep Gulf of Mexico.

  5. Spatial Structure and Activity of Sedimentary Microbial Communities Underlying a Beggiatoa spp. Mat in a Gulf of Mexico Hydrocarbon Seep

    PubMed Central

    Lloyd, Karen G.; Albert, Daniel B.; Biddle, Jennifer F.; Chanton, Jeffrey P.; Pizarro, Oscar; Teske, Andreas

    2010-01-01

    Background Subsurface fluids from deep-sea hydrocarbon seeps undergo methane- and sulfur-cycling microbial transformations near the sediment surface. Hydrocarbon seep habitats are naturally patchy, with a mosaic of active seep sediments and non-seep sediments. Microbial community shifts and changing activity patterns on small spatial scales from seep to non-seep sediment remain to be examined in a comprehensive habitat study. Methodology/Principal Findings We conducted a transect of biogeochemical measurements and gene expression related to methane- and sulfur-cycling at different sediment depths across a broad Beggiatoa spp. mat at Mississippi Canyon 118 (MC118) in the Gulf of Mexico. High process rates within the mat (∼400 cm and ∼10 cm from the mat's edge) contrasted with sharply diminished activity at ∼50 cm outside the mat, as shown by sulfate and methane concentration profiles, radiotracer rates of sulfate reduction and methane oxidation, and stable carbon isotopes. Likewise, 16S ribosomal rRNA, dsrAB (dissimilatory sulfite reductase) and mcrA (methyl coenzyme M reductase) mRNA transcripts of sulfate-reducing bacteria (Desulfobacteraceae and Desulfobulbaceae) and methane-cycling archaea (ANME-1 and ANME-2) were prevalent at the sediment surface under the mat and at its edge. Outside the mat at the surface, 16S rRNA sequences indicated mostly aerobes commonly found in seawater. The seep-related communities persisted at 12–20 cm depth inside and outside the mat. 16S rRNA transcripts and V6-tags reveal that bacterial and archaeal diversity underneath the mat are similar to each other, in contrast to oxic or microoxic habitats that have higher bacterial diversity. Conclusions/Significance The visual patchiness of microbial mats reflects sharp discontinuities in microbial community structure and activity over sub-meter spatial scales; these discontinuities have to be taken into account in geochemical and microbiological inventories of seep environments. In

  6. Stable isotope trophic patterns in echinoderm megafauna in close proximity to and remote from Gulf of Mexico lower slope hydrocarbon seeps

    NASA Astrophysics Data System (ADS)

    Carney, Robert Spencer

    2010-11-01

    Hydrocarbon-seep communities in the Gulf of Mexico have a high biomass that is exploited as a food source to varying degrees by the photosynthesis-dependent fauna inhabiting the surrounding mud bottom. A decline concurrent with ocean depth in detritus influx to that background habitat results in a much lower background biomass. The biomass contrast between population-rich seeps and depauperate mud bottom leads to the prediction that seep utilization by the background fauna should be extensive at all depths and should increase with depth. Species depth zonation makes like-species comparisons over the full depth of the Gulf of Mexico impossible. Seeps and normal bottom above 1000 m have different fauna from those below 1000 m. Lower slope seeps are surrounded by a fauna rich in echinoderm species, especially asteroids, ophiuroids, and holothuroids. All three taxa have species that are abundant within seeps and are probably endemic to them. They also contain species found only in mud background or within mud and seeps backgrounds. Tissue analyses of δ13C and δ15N of echinoderms collected by ROV within seeps and trawling away from seeps indicate a pattern of utilization similar to that found in upper slope seeps exploited by different taxa. Seastar and ophiuroid species abundant in or endemic to seeps have tissue isotope values reflecting seep chemosynthetic input via a free-living microbial detritus or predation. A single seep-endemic deposit-feeding holothuroid showed distinct seep tissue values. Background deposit-feeding holothuroids collected within seeps showed either no or only minor incorporation of seep carbon, indicating either a lack of access to seep detritus or short feeding times within the seep. A predicted extensive utilization of seep productivity at the deeper seeps was not found. Seeps may be relatively closed systems that require special adaptations of species in order for them to enter, exploit, and survive. Alternately, the surrounding deep

  7. Remote detection of hydrocarbon seeps

    SciTech Connect

    Barringer, A. R.

    1985-05-14

    A method of detecting hydrocarbon seeps in a sea or in earth is disclosed. The method involves interrogating aerosols formed above the sea or earth surface with an intense beam of primary light radiation generated aboard an aircraft or other vehicle. The spectral composition of the beam is selected to induce secondary light radiation in certain hydrocarbon materials contained in aerosols generated by hydrocarbon seeps rising to the sea or earth surface. The secondary light radiation is detected aboard the aircraft and subjected to spectral analysis to determine whether the composition of the aerosols is characteristic of aerosols generated by hydrocarbon seeps. Apparatus for implementing the method is also disclosed.

  8. Species Distribution and Population Connectivity of Deep-Sea Mussels at Hydrocarbon Seeps in the Gulf of Mexico

    PubMed Central

    Faure, Baptiste; Schaeffer, Stephen W.; Fisher, Charles R.

    2015-01-01

    Hydrocarbon seepage is widespread and patchy in the Gulf of Mexico, and six species of symbiont containing bathymodiolin mussels are found on active seeps over wide and overlapping depth and geographic ranges. We use mitochondrial genes to discriminate among the previously known and a newly discovered species and to assess the connectivity among populations of the same species in the northern Gulf of Mexico (GoM). Our results generally validate the morphologically based distribution of the three previously known GoM species of Bathymodiolus, although we found that approximately 10% of the morphologically based identifications were incorrect and this resulted in some inaccuracies with respect to their previously assigned depth and geographical distribution patterns. These data allowed us to confirm that sympatry of two species of Bathymodiolus within a single patch of mussels is common. A new species of bathymodiolin, Bathymodiolus sp. nov., closely related to B. heckerae was also discovered. The two species live at the same depths but have not been found in sympatry and both have small effective population sizes. We found evidence for genetic structure within populations of the three species of Bathymodiolinae for which we had samples from multiple sites and suggest limited connectivity for populations at some sites. Despite relatively small sample sizes, genetic diversity indices suggest the largest population sizes for B. childressi and Tamu fisheri and the smallest for B. heckerae and B. sp. nov. among the GoM bathymodiolins. Moreover, we detected an excess of rare variants indicating recent demographic changes and population expansions for the four species of bathymodiolins from the Gulf of Mexico. PMID:25859657

  9. Filamentous sulfide-oxidizing bacteria at hydrocarbon seeps of the Gulf of Mexico.

    PubMed

    Larkin, J M; Henk, M C

    1996-01-01

    Mats consisting of the large sulfide-oxidizing bacterium, Beggiatoa, were collected from the sediment/water interface at several locations in the Gulf of Mexico. The collection sites were associated with the presence of petroleum hydrocarbons or the microbial breakdown products of the hydrocarbons. The morphologies of the mats varied with the nature of the underlying sediments, and some mats were pigmented either yellow or orange instead of the usual white. At one site, beggiatoas were found that had a diameter of nearly 200 mu m, making them the largest prokaryotic organism known. In filaments with a diameter of over approximately 10 mu m the cytoplasm was restricted to a thin layer immediately underlying the cell membrane, and the majority of the cell consisted of a vacuole with unknown contents. Beggiatoa filaments often rotated as they moved by gliding. Parallel rows of 15 nm diameter pores were found on the surface of the beggiatoas. The pores may have been wound in a spiral fashion around the cell. These pores may be involved in the gliding motility of the bacteria by the motion imparted by the excretion of slime through the pores. Several structures with the typical morphology of prokaryotic cells but lacking a cell wall were found within the vacuolar and cytoplasmic portions of the hollow beggiatoas. Some of these internal "symbionts" ultrastructurally resembled methanotrophic bacteria like those that have been seen in animals taken from vent areas. Other symbionts ultrastructurally resembled autotrophic bacteria with carboxysome-like structures. These internal symbionts may enable the Beggiatoa to grow in different environments on different carbon sources. They also provide important evidence for the endosymbiotic theory of the evolution of internal organelles of eukaryotic organisms. PMID:8820662

  10. Northern Gulf of Mexico hydrocarbon seep communities: Implications to the petroleum industry

    SciTech Connect

    Avent, R.M. )

    1990-05-01

    Most animals consume organic food sources based on primary productivity at the base of the food web. Little food reaches deep-sea bottom animals which are usually small, fragile, and sparsely distributed. Recent discoveries of chemosynthetic organisms worldwide have led to investigations into the taxonomy. ecology, biochemistry, and physiology of these forms. The dominant animals in these communities, several large species of vestimentiferan tube worms and bivalve mollusks, energetically use dissolved gases (primarily methane and hydrogen sulfide) issuing from the sea bottom under certain geological conditions. Endosymbiotic bacteria aid metabolic pathways. The large chemosynthetic animals and their dense populations (orders of magnitude over background) are the exceptions that prove the rule that food is an important limiting factor in the deep sea. The discovery of relatively shallow, luxuriant gas-seep communities on the Louisiana upper slope raises concerns on the environmental effects of nearby petroleum operations. To protect these communities, the Minerals Management Service requires photographic bottom surveys in depths from 400 to 900 m if geophysical evidence of seeps (wipeout zones or streams of bubbles) is found. If found near proposed well locations, high-density communities must be avoided thereby preventing physical damage from any structure. Deep-sea community surveys can be expensive and can result in alternative siting plans and development delays. But Minerals Management Service's requirements should conserve these shallow communities that have considerable value as natural laboratories accessible to academic study. We know little about the permanence, dynamics, recruitment recovery potential. and life requirements of chemosynthetic communities. Additional studies, funded by the Minerals Management Service, have been proposed.

  11. Short- and Long-Term Dynamics of Gas Hydrate at GC600: A Gulf of Mexico Hydrocarbon Seep

    NASA Astrophysics Data System (ADS)

    MacDonald, I. R.; Johansen, C.; Silva, M.; Daneshgar, S.; Garcia-Pineda, O. G.; Shedd, W. W.

    2014-12-01

    The GC600 hydrocarbon seep is located at 1200 m in the northern Gulf of Mexico (GOM). Satellite data show it to be one of the most prolific sources of natural oil slicks in the entire GOM. We mapped its seafloor oil and gas vents with 3-D seismic, swath-bathymetry acoustics and submersible observations, documenting gas hydrate deposits, brine pools, benthic fauna, and authigenic carbonates. Geophysical profiles show subbottom locations of salt bodies and migration conduits. We deployed time-lapse imaging systems focused on individual vents to quantify release rates. Oil and gas flow upward along the flanks of an allochthonous salt body from source rocks at 10,000 m and migrate to the seafloor from faults emanating from the salt. Venting to the water column and surface consists of oily bubbles and occurs in two fields separated by ~1 km. The NW vent field (Megaplume) appears to be a more recent expression and hosts about three highly active vents; while the SE vent field (Birthday Candles) hosts more than 10 vents that are generally slower. We measured discharge rates of 2.6 cm3 s-1 and Megaplume and 0.09 cm3 s-1 at Birthday Candles. Although surface deposits of gas hydrate were evident at both vent fields, the Birthday Candles area featured dozens of conical mounds formed by gas hydrate that were dark brown due to large amounts of liquid oil perfused throughout the deposits. Large brine pools indicated gas hydrate formation at the seafloor. Venting occurred in horizontal fissures on the mounds, in which oil and hydrate combined to form short-lived chimneys and balloon-like structures. Ice worms (Hesiocaeca methanicola) were extremely abundant in burrows extending from the sediment into the gas hydrate. Proceeding farther to the SE, venting is reduced and absent, but surface carbonate deposits suggest relict gas hydrate mounds. We propose that the NW to SE trend at GC600 encompasses the progressive development of a biogeochemical filter that sequesters and

  12. Gulf of Mexico hydrocarbon seep communities. V. Biofacies and shell orientation of autochthonous shell beds below storm wave base

    SciTech Connect

    Callender, W.R.; Staff, G.M.; Powell, E.N.; MacDonald, I.R. )

    1990-02-01

    Clam and mussel assemblages associated with petroleum seepage on the Louisiana continental slope form the only substantial shell accumulations below storm wave base on the northwestern Gulf of Mexico shelf and slope. Four distinct biofacies are present at the seeps, dominated respectively by mussels, lucinid clams, vesicomyid clams and tubeworms. Each primary seep site is typically composed of a series of not necessarily contiguous, autochthonous beds dominated by one biofacies. Mussels and tubeworms often co-occur, but neither normally co-occur with lucinid or vesicomyid clams. Lucinid and vesicomyid clam beds have the best chance of preservation. Despite essentially undisturbed accumulation in quiet water below storm wave base, concavity ratios rarely differ from 1:1 and frequency of articulation may be low. Dominantly concave-up valves previously reported in quiet water may result from man's fishing activities. Significant variability in shell orientation, frequency of articulation and concavity ratio between adjacent samples indicates that many individual stratigraphically-equivalent samples should be used in any taphofacies analysis of assemblages formed in low-energy environments. Lucinid beds which form below the sediment surface and vesicomyid beds which form on the sediment surface differed significantly in shell orientation and articulation frequency. Assemblages forming below storm wave base in low-energy environments may comprise a wide variety of taphofacies depending upon whether formation occurs primarily beneath the sediment surface or on the sediment surface, despite contemporaneous formation under similar environmental conditions.

  13. Population structure of two deep sea tubeworms, Lamellibrachia luymesi and Seepiophila jonesi, from the hydrocarbon seeps of the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    McMullin, Erin R.; Nelson, Kimberlyn; Fisher, Charles R.; Schaeffer, Stephen W.

    2010-11-01

    Vestimentiferan tubeworms are a group of large sessile marine polychaete annelids (family Siboglinidae) found in the regions of hydrothermal venting or seepage of the reduced chemical hydrogen sulfide. Hydrocarbon seeps on the Louisiana Slope of the Gulf of Mexico support large communities of the co-occurring vestimentiferan species Lamellibrachia luymesi and Seepiophila jonesi. These sessile species have the opportunity to disperse between the patchy sites of active seepage on the seafloor during a planktonic larval stage. However, it is unclear whether dispersal occurs at a local or global scale. Four ( L. luymesi) and seven ( S. jonesi) microsatellite loci were used to test for population substructure among ten hydrocarbon seep sites on the Louisiana Slope. Both species showed high levels of allelic diversity, averaging 18.5 ( L. luymesi) and 22 ( S. jonesi) alleles/locus, respectively, and high observed heterozygosity at all microsatellite loci (0.71-0.9 in L. luymesi, 0.27-0.84 in S. jonesi). The two species showed a significant deficiency in heterozygotes compared to that predicted under the Hardy-Weinberg equilibrium. L. luymesi showed a small but significant amount of population structure, with a positive correlation between genetic and geographic distance among the sample sites spanning 540 km. S. jonesi, in contrast, showed no evidence for isolation by distance, but did show a significant genetic difference between aggregations of different ages. These results suggest that these two species differ in how larvae are able to colonize new seep sites through space ( L. luymesi) and though time ( S. jonesi).

  14. Macro-Ecology of Gulf of Mexico Cold Seeps

    NASA Astrophysics Data System (ADS)

    Cordes, Erik E.; Bergquist, Derk C.; Fisher, Charles R.

    2009-01-01

    Shortly after the discovery of chemosynthetic ecosystems at deep-sea hydrothermal vents, similar ecosystems were found at cold seeps in the Gulf of Mexico. Over the past two decades, these sites have become model systems for understanding the physiology of the symbiont-containing megafauna and the ecology of seep communities worldwide. Symbiont-containing bivalves and siboglinid polychaetes dominate the communities, including five bathymodiolin mussel species and six vestimentiferan (siboglinid polychaete) species in the Gulf of Mexico. The mussels include the first described examples of methanotrophic symbiosis and dual methanotrophic/thiotrophic symbiosis. Studies with the vestimentiferans have demonstrated their potential for extreme longevity and their ability to use posterior structures for subsurface exchange of dissolved metabolites. Ecological investigations have demonstrated that the vestimentiferans function as ecosystem engineers and identified a community succession sequence from a specialized high-biomass endemic community to a low-biomass community of background fauna over the life of a hydrocarbon seep site.

  15. Elevated surface chlorophyll associated with natural oil seeps in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    D'Souza, N. A.; Subramaniam, A.; Juhl, A. R.; Hafez, M.; Chekalyuk, A.; Phan, S.; Yan, B.; MacDonald, I. R.; Weber, S. C.; Montoya, J. P.

    2016-03-01

    Natural hydrocarbon seeps occur on the sea floor along continental margins, and account for up to 47% of the oil released into the oceans. Hydrocarbon seeps are known to support local benthic productivity, but little is known about their impact on photosynthetic organisms in the overlying water column. Here we present observations with high temporal and spatial resolution of chlorophyll concentrations in the northern Gulf of Mexico using in situ and shipboard flow-through fluorescence measurements from May to July 2012, as well as an analysis of ocean-colour satellite images from 1997 to 2007. All three methods reveal elevated chlorophyll concentrations in waters influenced by natural hydrocarbon seeps. Temperature and nutrient profiles above seep sites suggest that nutrient-rich water upwells from depth, which may facilitate phytoplankton growth and thus support the higher chlorophyll concentrations observed. Because upwelling occurs at natural seep locations around the world, we conclude that offshore hydrocarbon seeps, and perhaps other types of deep ocean vents and seeps at depths exceeding 1,000 m, may influence biogeochemistry and productivity of the overlying water column.

  16. Investigating Hydrocarbon Seep Environments with High-Resolution, Three-Dimensional Geographic Visualizations.

    NASA Astrophysics Data System (ADS)

    Doolittle, D. F.; Gharib, J. J.; Mitchell, G. A.

    2015-12-01

    Detailed photographic imagery and bathymetric maps of the seafloor acquired by deep submergence vehicles such as Autonomous Underwater Vehicles (AUV) and Remotely Operated Vehicles (ROV) are expanding how scientists and the public view and ultimately understand the seafloor and the processes that modify it. Several recently acquired optical and acoustic datasets, collected during ECOGIG (Ecosystem Impacts of Oil and Gas Inputs to the Gulf) and other Gulf of Mexico expeditions using the National Institute for Undersea Science Technology (NIUST) Eagle Ray, and Mola Mola AUVs, have been fused with lower resolution data to create unique three-dimensional geovisualizations. Included in these data are multi-scale and multi-resolution visualizations over hydrocarbon seeps and seep related features. Resolution of the data range from 10s of mm to 10s of m. When multi-resolution data is integrated into a single three-dimensional visual environment, new insights into seafloor and seep processes can be obtained from the intuitive nature of three-dimensional data exploration. We provide examples and demonstrate how integration of multibeam bathymetry, seafloor backscatter data, sub-bottom profiler data, textured photomosaics, and hull-mounted multibeam acoustic midwater imagery are made into a series a three-dimensional geovisualizations of actively seeping sites and associated chemosynthetic communities. From these combined and merged datasets, insights on seep community structure, morphology, ecology, fluid migration dynamics, and process geomorphology can be investigated from new spatial perspectives. Such datasets also promote valuable inter-comparisons of sensor resolution and performance.

  17. Bacterioplankton growth and production at the Louisiana hydrocarbon seeps

    NASA Astrophysics Data System (ADS)

    Larock, P. A.; Hyun, J.-H.; Bennison, B. W.

    1994-06-01

    The growth rate and potential production of bacterioplankton in cold hydrocarbon seeps located along the Louisiana coast were determined using a pulse-labeling technique. Surprisingly, community doubling times are on the order of 1.1 h, which compares to laboratory-grown cultures. We also found that there are differences in growth rates on relatively small geographic scales, suggesting the influence of site-specific geological features (e.g., gas hydrate mounds). Proceeding downslope to deeper waters, methane-oxidizing bacteria appeared to play a more significant role in community productivity. These preliminary experiments indicated, quite unexpectedly, that water column microbes are growing at a more rapid rate than in any other marine system so far studied and that methane may serve as a primary nutrient (carbon) source in these seep-associated microbial assemblages.

  18. How oil seeps, discoveries relate in deepwater Gulf of Mexico

    SciTech Connect

    Sassen, R.; Brooks, J.M.; Kennicutt, M.C. II; MacDonald, I.R.; Guinasso, N.L. Jr. )

    1993-04-19

    Biomarker compounds of crude oils from deep-water Gulf of Mexico seeps are consistent with an origin from deeply-buried Mesozoic carbonate source rocks. The known oil reserves, however, are trapped in shallow Miocene to Pleistocene sands. Several kilometers of vertical migration must be invoked to explain the presence of crude oil from deep sources in shallow reservoir sands. Salt-related fractures and faults serve as efficient conduits for vertical migration through the thick sedimentary section. Thermal history models suggest that oil migration off Louisiana started during the Miocene and continues at present in some areas. The paper describes visual inspection of seeps; gives an overview of the deep Gulf; and discusses seeps and fields, case histories, and frontier basins.

  19. Seep Mapping: Using NOAA Ship Okeanos Explorer Data to Visualize the Physical Environments of Seeps in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Auner, L.; McKenna, L.; Lobecker, E.; Sowers, D.

    2014-12-01

    More than 550 possible gaseous seeps were previously identified along the continental margin in the northwestern Gulf of Mexico using water-column acoustic backscatter data collected on the NOAA Ship Okeanos Explorer in the spring of 2014. Although the presence of macro-seeps can only be verified through visual confirmation, several studies suggest that gaseous bubbles emitted by seeps are uniquely detected in sonar water-column backscatter returns (Judd and Hovland, 1992; Nikolovska et al., 2008; Weber et al., 2012). In this study, more than 200 seeps were independently identified from a subset of water-column backscatter data collected in March and April, 2014. Additional data collected aboard the Okeanos Explorer includes bathymetry, seafloor backscatter, sub-bottom seismic reflection profiles, and ROV video footage. These datasets, along with calculated geomorphic parameters such as slope, were used to develop specialized mapping products to display physical characteristics of the seafloor and subsurface surrounding a number of gaseous seeps. Preliminary results indicate that seeps occur in a wide variety of geomorphic settings, including the edges of salt domes, and at depths ranging from approximately 300 meters to 1,100 meters. Study results could be used to make predictions about where seeps are most likely to be detected along the continental margin of the northwestern Gulf of Mexico. These predictions could inform future efforts to study seeps and their associated biological communities within the study area or aid in the development of larger scale seep characterization and predictive modeling.

  20. Methane and sulfur cycling in terrestrial hydrocarbon seeps

    NASA Astrophysics Data System (ADS)

    Lin, L.; Wang, P.; Cheng, T.; Ling, Y.; Sun, C.; Chen, Y.; Wang, C.; Wu, J.; Chu, P.

    2009-12-01

    Hydrocarbon seeps are ubiquitous in marine and terrestrial environments where gaseous fluids with unconsolidated, fine-grained sediments ascend along fractures prior to being discharged on seafloor or land surface. Complex geological and microbial processes are involved in the sequestration of photosynthetically produced organic carbon into deep subsurface environments and cycling of methane and carbon dioxide back to atmosphere. Extensive studies conducted on marine settings indicate that geochemical stratification in sediment porewater is dynamically regulated by various microbial processes. Whether the experience accumulated over the decadal observation on marine settings could be applied to shallow and deep biosphere beneath terrestrial hydrocarbon seeps remains poorly constrained. To address the issue about how carbon and sulfur compounds were cycled in terrestrial hydrocarbon seeps, this presentation summarized the results obtained from samples collected in two sites (one at 60C and the other at 27C) of southwestern Taiwan. These sites characterized by continuously voluminous discharge of hydrocarbons were considered as the model analogs that would provide better constraints on microbial processes at ambient and high temperatures in seep-related subsurface environments. Our findings indicated that sulfate reduction and methanogenesis were active at temperatures up to 80C. Sulfate reducing and fermentative populations shifted substantially upon incubations at different temperatures, suggesting that degradation of organic carbon could only proceed with collaborative interactions among metabolisms. The proliferation of mesophilic sulfate reduction in sulfate-deprived terrestrial environments appears to be best facilitated by atmospheric oxidation of pyrite inherited in sediments. Sulfate produced in surface environments migrated downward to fuel sulfate reduction coupled to anaerobic methane oxidation near the sulfate-to-methane transition. Of various

  1. Sulfur biogeochemistry of cold seeps in the Green Canyon region of the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Formolo, Michael J.; Lyons, Timothy W.

    2013-10-01

    Cold seeps in the Gulf of Mexico provide a natural laboratory to study biogeochemical cycling of sulfur, carbon, and oxygen at hydrate- and hydrocarbon-rich deep marine settings with obvious additional relevance to studies of diverse modern and ancient seeps. Of particular interest are the sulfur isotope signatures of microbial sulfate reduction coupled to anaerobic oxidation of methane and other non-methane liquid and gaseous hydrocarbons. Whereas most of the published sulfur isotope data from cold seep systems pertain to pore-water species, our study integrates both solid and dissolved sulfur: acid-volatile sulfides (SAVS), pyrite (Spy), elemental sulfur (S°), dissolved sulfate and ΣH2S. Modeled and 35SO42- reduction rates and δ13C and δ18O data for authigenic carbonates are integrated within this sulfur framework. Our results indicate extreme variability over narrow spatial and temporal scales within short distances (meters) from active seeps. High rates of microbial sulfate reduction can lead to complete consumption of the sulfate within the upper few centimeters of burial, while meters away the sulfate profile shows little depletion. Such small-scale variability must reflect the structure and temporal dynamics of hydrocarbon migration in the presence of low amounts of background organic matter. Our past work demonstrated that electron donors other than methane drive significant levels of microbial activity at these seeps, and very recent work has demonstrated that oxidation of higher chain volatile hydrocarbons can contribute to the high levels of microbial activity. These findings are consistent with our new results. Elevated concentrations of pyrite and diagenetic carbonate relative to background sediments are diagnostic of active seepage, yet the S isotopes tell more complex stories. Low levels of the transient, 'instantaneous' products of S cycling-AVS and S°-show high δ34S values that increase with depth. Most of the pyrite formation, however, seems

  2. Symbiont-driven sulfur crystal formation in a thiotrophic symbiosis from deep-sea hydrocarbon seeps

    PubMed Central

    Eichinger, Irmgard; Schmitz-Esser, Stephan; Schmid, Markus; Fisher, Charles R; Bright, Monika

    2014-01-01

    The siboglinid tubeworm Sclerolinum contortum symbiosis inhabits sulfidic sediments at deep-sea hydrocarbon seeps in the Gulf of Mexico. A single symbiont phylotype in the symbiont-housing organ is inferred from phylogenetic analyses of the 16S ribosomal ribonucleic acid (16S rRNA) gene and fluorescent in situ hybridization. The phylotype we studied here, and a previous study from an arctic hydrocarbon seep population, reveal identical 16S rRNA symbiont gene sequences. While sulfide is apparently the energy source for the symbionts (and ultimately the gutless host), both partners also have to cope with its toxicity. This study demonstrates abundant large sulfur crystals restricted to the trophosome area. Based on Raman microspectroscopy and energy dispersive X-ray analysis, these crystals have the same S8 sulfur configuration as the recently described small sulfur vesicles formed in the symbionts. The crystals reside adjacent to the symbionts in the trophosome. This suggests that their formation is either extra- or intracellular in symbionts. We propose that formation of these crystals provides both energy-storage compounds for the symbionts and serves the symbiosis by removing excess toxic sulfide from host tissues. This symbiont-mediated sulfide detoxification may have been crucial for the establishment of thiotrophic symbiosis and continues to remain an important function of the symbionts. PMID:24992535

  3. Hydrocarbon geochemistry of cold seeps in the Monterey Bay National Marine Sanctuary

    USGS Publications Warehouse

    Lorenson, T.D.; Kvenvolden, K.A.; Hostettler, F.D.; Rosenbauer, R.J.; Orange, D.L.; Martin, J.B.

    2002-01-01

    Samples from four geographically and tectonically discrete cold seeps named Clam Flat, Clamfield, Horseshoe Scarp South, and Tubeworm City, within the Monterey Bay National Marine Sanctuary were analyzed for their hydrocarbon content. The sediment contains gaseous hydrocarbons and CO2, as well as high molecular weight aliphatic and aromatic hydrocarbons with various combinations of thermogenic and biogenic contributions from petroleum, marine, and terrigenous sources. Of particular interest is the cold seep site at Clamfield which is characterized by the presence of thermogenic hydrocarbons including oil that can likely be correlated with oil-saturated strata at Majors Creek near Davenport, CA, USA. At Clam Flat, the evidence for thermogenic hydrocarbons is equivocal. At Horseshoe Scarp South and Tubeworm City, hydrocarbon gases, mainly methane, are likely microbial in origin. These varied sources of hydrocarbon gases highlight the diverse chemical systems that appear at cold seep communities. ?? 2002 Elsevier Science B.V. All rights reserved.

  4. Co-Occurrence of Nitrate Reduction and Anaerobic Oxidation of Methane in Gulf of Mexico Cold Seep Habitats

    NASA Astrophysics Data System (ADS)

    Fields, L.; Joye, S. B.

    2014-12-01

    Cold seeps are abundant in the Gulf of Mexico; they are fuelled by methane gas and hydrocarbon seepage at the seafloor and support diverse chemosynthetic microbial communities. Microorganisms form the base of the food chain at cold seeps, and high rates of anaerobic oxidation of methane (AOM) are characteristic of these methane-rich environments. While sulfate is often the electron acceptor for AOM in cold seep environments, recent evidence suggests that AOM can also be coupled to nitrate reduction. Little is known about nitrogen cycling in these habitats, though recent work indicates that denitrification is an important process in oily and gassy seep sediments. The co-occurrence of nitrate reduction and AOM suggests a potential coupling between the two processes in our study area. We used stable isotope (15N) tracer techniques to measure the capacity of Northern Gulf of Mexico cold seep sediments to reduce nitrate by denitrification and anammox. These measurements were made in surface and sub-surface sediments in conjunction with measurements of AOM, and with quantification of various geochemical and molecular characteristics. Here, we present our measurements of denitrification and anammox capacity in the context of environmental characteristics. Additionally, we examine spatial trends in the co-occurrence of AOM and nitrate reduction in these sediments.

  5. Bacterial symbionts of Bathymodiolus mussels and Escarpia tubeworms from Chapopote, an asphalt seep in the Southern Gulf of Mexico.

    PubMed

    Raggi, L; Schubotz, F; Hinrichs, K-U; Dubilier, N; Petersen, J M

    2013-07-01

    Chemosynthetic life was recently discovered at Chapopote, an asphalt hydrocarbon seep in the southern Gulf of Mexico. Preliminary morphological analyses indicated that one tubeworm and two mussel species colonize Chapopote. Our molecular analyses identified the tubeworm as Escarpia sp., and the mussels as Bathymodiolus heckerae and B. brooksi. Comparative 16S rRNA analysis and FISH showed that all three species harbour intracellular sulfur-oxidizing symbionts highly similar or identical to those found in the same host species from northern Gulf of Mexico (nGoM). The mussels also harbour methane-oxidizing symbionts, and these shared highly similar to identical 16S rRNA sequences to their nGoM conspecifics. We discovered a novel symbiont in B. heckerae, which is closely related to hydrocarbon-degrading bacteria of the genus Cycloclasticus. In B. heckerae, we found key genes for the use of aromatic compounds, and its stable carbon isotope values were consistently higher than B. brooksi, indicating that the novel symbiont might use isotopically heavy aromatic hydrocarbons from the asphalt seep. This discovery is particularly intriguing because until now only methane and reduced sulfur compounds have been shown to power cold-seep chemosynthetic symbioses. The abundant hydrocarbons available at Chapopote would provide these mussel symbioses with a rich source of nutrition. PMID:23279012

  6. Satellite SAR inventory of Gulf of Mexico oil seeps and shallow gas hydrates

    NASA Astrophysics Data System (ADS)

    Garcia, O.; MacDonald, I. R.; Zimmer, B.; Shedd, W.; Frye, M.

    2009-04-01

    Satellite synthetic aperture radar (SAR) images from the RADARSAT platform were used to detect and inventory persistent layers of oil released from natural seeps in the Gulf of Mexico. Previously published inventories of natural oil seeps in the Gulf have been limited in scope and have relied on manual interpretation of satellite images (Mitchell et al. 1999; De Beukelaer et al. 2003). We developed a texture classifying neural network algorithm (TCNNA) to rapidly identify floating oil-layers in a semi-supervised operation. Oil layers, known as slicks, were recognized as long (10 km), narrow (100 m), often curvilinear streaks with distinct points of origin where oil reaches the ocean surface. After training the TCNNA over known seep areas and under a range of environmental and viewing conditions, the procedure was applied to 426 separate images that covered ocean areas of 100x100 km (Standard Beam Mode), 102 images that covered ocean areas of 450x450 km(ScanSAR Wide Beam Mode), and 84 images that covered ocean areas of 300x300 km (ScanSAR Narrow Beam Mode). This image data-set was collected between 1994 and 2007. It covered the entire Gulf of Mexico with a repeat rate of 4 to109, with the highest concentration over the continental slope. This effort identified a total of 4957 slicks among all the images. Of these, 287 appeared a single time in isolated locations and may therefore be false targets. The remaining slicks appeared in groups of up to 9 separate features, clustered in areas of 1 to 6.5 km across. When slicks appear within the same area in repeated images, they are judged to have a persistent source—a bubbling vent on the seafloor (MacDonald et al. 2002). Persistent sources represent geologic formations defined by migrating hydrocarbons that may include multiple separate vents. A total of 559 formations were defined by repeated imaging; these comprised a maximum of 1995 and a minimum of 1263 individual vents. This total was distributed between U

  7. Cold-seep carbonates of the middle and lower continental slope, northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Roberts, Harry H.; Feng, Dong; Joye, Samantha B.

    2010-11-01

    Authigenic carbonates from cold seeps on the middle and lower continental slope of the northern Gulf of Mexico (GOM) exhibit a wide range of mineralogical and stable isotopic compositions. These carbonates consist of concretions and nodules in surface sediments, hardgrounds of crusts and isolated slabs, and mounded buildups of blocks and slabs of up to over 10 meters in relief above the surrounding seafloor. Mineralogically, the carbonates are dominated by high-Mg calcite (HMC) and aragonite. However, low levels (<5 wt%) of dolomite are present in most samples. Petrographically, Mg-calcite peloidal matrix and acicular to botryoidal aragonitic void-filling cements are the most frequent associations. The carbon isotopic compositions of the carbonates range from -60.8 to 14.0‰ PDB, indicating complex carbon sources that include 13C-depleted biogenic and thermogenic methane, biodegraded crude oil, seawater CO2, and 13C-enriched residual CO2 from methanogenesis. A similarly large variability in δ18O values (2.5 to 6.7‰ PDB) demonstrates the geochemical complexity of the slope, with some samples pointing toward an 18O-enriched oxygen source that is possibly related to advection of 18O-enriched formation water and/or to the decomposition of gas hydrate. A considerable range of mineralogical and isotopic variations in cold-seep carbonate composition was noted even within individual study sites. However, common trends occur across multiple geographic areas. This situation suggests that local controls on fluid and gas flux, types of seep hydrocarbons, the presence or absence of gas hydrate in the near-surface sediment, and chemosynthetic communities, as well as the temporal evolution of the local hydrocarbon reservoir, all may play a part in determining carbonate mineralogy and isotope geochemistry. The carbon isotope data clearly indicate that between-site variation is greater than within-site variation. Seep carbonates formed on the middle and lower continental slope

  8. Short-chain alkane cycling in deep Gulf of Mexico cold-seep sediments

    NASA Astrophysics Data System (ADS)

    Sibert, R.; Joye, S. B.; Hunter, K.

    2015-12-01

    Mixtures of light hydrocarbon gases are common in deep Gulf of Mexico cold-seep sediments, and are typically dissolved in pore fluids, adsorbed to sediment particles, trapped in methane ice, or as free gas. The dominant component in these natural gas mixtures is usually methane (>80% C1), but ethane (C2) and propane (C3) are nearly always present in trace amounts (<1% total). The processes that control the concentration and isotopic signature of these gases in sediments are well explained for methane, but the controls for C2/C3 cycling are still a relative mystery. Methane production proceeds in deep anoxic sediments by either 1) thermocatalytic cracking of fossil organic matter, or 2) as a direct product of microbial metabolism, i.e. methanogenesis. In surface sediments, it appears that both microbial consumption and chemical deposition of methane (i.e. as methane clathrate) ensures that >95% of the methane produced at depth never reaches the water column. Production of C1 and C2 in deep-sea sediments has been historically attributed only to thermocatalytic processes, though limited data suggests production of C2/C3 compounds through the activity of archaea at depth. Furthermore, carbon isotopic data on ethane and propane from deep cores of Gulf of Mexico sediments suggest alkanogenesis at >3 m depth in the sediment column and alkane oxidation in uppermost oxidant-rich sediments. Additional studies have also isolated microorganisms capable of oxidizing ethane and propane in the laboratory, but field studies of microbial-driven dynamics of C2/C3 gases in cold-seep sediments are rare. Here, we present the results of a series of incubation experiments using sediment slurries culled from surface sediments from one of the most prolific natural oil and gas seeps in the Gulf of Mexico. Rates of alkane oxidation were measured under a variety of conditions to assess the surface-driven microbial controls on C2/C3 cycling in cold-seep environments. Such microbial processes

  9. Anaerobic degradation of propane and butane by sulfate-reducing bacteria enriched from marine hydrocarbon cold seeps

    PubMed Central

    Jaekel, Ulrike; Musat, Niculina; Adam, Birgit; Kuypers, Marcel; Grundmann, Olav; Musat, Florin

    2013-01-01

    The short-chain, non-methane hydrocarbons propane and butane can contribute significantly to the carbon and sulfur cycles in marine environments affected by oil or natural gas seepage. In the present study, we enriched and identified novel propane and butane-degrading sulfate reducers from marine oil and gas cold seeps in the Gulf of Mexico and Hydrate Ridge. The enrichment cultures obtained were able to degrade simultaneously propane and butane, but not other gaseous alkanes. They were cold-adapted, showing highest sulfate-reduction rates between 16 and 20 °C. Analysis of 16S rRNA gene libraries, followed by whole-cell hybridizations with sequence-specific oligonucleotide probes showed that each enrichment culture was dominated by a unique phylotype affiliated with the Desulfosarcina-Desulfococcus cluster within the Deltaproteobacteria. These phylotypes formed a distinct phylogenetic cluster of propane and butane degraders, including sequences from environments associated with hydrocarbon seeps. Incubations with 13C-labeled substrates, hybridizations with sequence-specific probes and nanoSIMS analyses showed that cells of the dominant phylotypes were the first to become enriched in 13C, demonstrating that they were directly involved in hydrocarbon degradation. Furthermore, using the nanoSIMS data, carbon assimilation rates were calculated for the dominant cells in each enrichment culture. PMID:23254512

  10. HYFLUX: Satellite Exploration of Natural Hydrocarbon Seeps and Discovery of a Methane Hydrate Mound at GC600

    NASA Astrophysics Data System (ADS)

    Garcia-Pineda, O. G.; MacDonald, I. R.; Shedd, W.; Zimmer, B.

    2009-12-01

    Analysis of natural hydrocarbon seeps is important to improve our understanding of methane flux from deeper sediments to the water column. In order to quantify natural hydrocarbon seep formations in the Northern Gulf of Mexico, a set of 686 Synthetic Aperture Radar (SAR) images was analyzed using the Texture Classifying Neural Network Algorithm (TCNNA), which processes SAR data to delineate oil slicks. This analysis resulted in a characterization of 396 natural seep sites distributed in the northern GOM. Within these sites, a maximum of 1248 individual vents where identified. Oil reaching the sea-surface is deflected from its source during transit through the water column. This presentation describes a method for estimating locations of active oil vents based on repeated slick detection in SAR. One of the most active seep formations was detected in MMS lease block GC600. A total of 82 SAR scenes (collected by RADARSAT-1 from 1995 to 2007) was processed covering this region. Using TCNNA the area covered by each slick was computed and Oil Slicks Origins (OSO) were selected as single points within detected oil slicks. At this site, oil slick signatures had lengths up to 74 km and up to 27 km^2 of area. Using SAR and TCNNA, four active vents were identified in this seep formation. The geostatistical mean centroid among all detections indicated a location along a ridge-line at ~1200m. Sea truth observations with an ROV, confirmed that the estimated location of vents had a maximum offset of ~30 m from their actual locations on the seafloor. At the largest vent, a 3-m high, 12-m long mound of oil-saturated gas hydrate was observed. The outcrop contained thousands of ice worms and numerous semi-rigid chimneys from where oily bubbles were escaping in a continuous stream. Three additional vents were found along the ridge; these had lower apparent flow, but were also plugged with gas hydrate mounds. These results support use of SAR data for precise delineation of active seep

  11. Chemoautolithotrophic Primary Production as a Fuel for Heterotrophs in Hydrocarbon Seeps: an Examination of Mobile Benthic Fauna and Seep Residents

    NASA Astrophysics Data System (ADS)

    Macavoy, S. E.; Morgan, E.; Fisher, C. R.; Carney, R. S.; Macko, S. A.

    2006-05-01

    The continental slope of the Gulf of Mexico supports dense aggregations of tube worms and mussels that are symbiotic with chemoautolithotrophic bacteria. Associated with these communities are numerous heterotrophic fauna plus free-living bacteria. The usage of chemosynthetic production by invertebrate fauna within or near the seeps is largely unknown. Here we examine the stable C, N and S isotope signatures of fauna from 2 chemosynthetic communities to identify ranges of chemoautolithotrophic primary production and determine the usage of that primary production by heterotrophic invertebrates. The isotope range for chemosynthetic production is different between sites. A seep dominated by methane-utilizing mussels (GC233) had the most depleted d13C and d15N (-50 to -65° and -9 to -12°, respectively) but most enriched d34S (11 to 6°). A site dominated by both tube worms and mussels (GC 234) there were two sources of C, one between -24 and -30° and another of approximately -40°. d15N and d34S at GC234 ranged from 1 to 5° and -10 to 6°, respectively. We estimate that hagfish captured 1 km from the communities derived at least 10 percent of their C from chemosynthetic sources. Giant isopods, captured with the hagfish show negligible chemosynthetic usage.

  12. Geochemical analysis of potash mine seep oils, collapsed breccia pipe oil shows and selected crude oils, Eddy County, New Mexico

    USGS Publications Warehouse

    Palacas, J.G.; Snyder, R.P.; Baysinger, J.P.; Threlkeld, C.N.

    1982-01-01

    Oil shows, in the form of oil stains and bleeding oil, in core samples from two breccia pipes, Hills A and C, Eddy County, New Mexico, and seepage oils in a potash mine near Hill C breccia pipe are geochemically similar. The geochemical similarities strongly suggest that they belong to the same family of oils and were derived from similar sources. The oils are relatively high in sulfur (0.89 to 1.23 percent), rich in hydrocarbons (average 82 percent), relatively high in saturated hydrocarbon/aromatic hydrocarbon ratios (average 2.9), and based on analysis of seep oils alone, have a low API gravity (average 19.4?). The oils are for the most part severely biodegraded as attested by the loss of n-paraffin molecules. Geochemical comparison of seven crude oils collected in the vicinity of the breccia pipes indicates that the Yates oils are the likely source of the above family of oils. Six barrels of crude oil that were dumped into a potash exploration borehole near Hill C breccia pipe, to release stuck casing, are considered an unlikely source of the breccia pipe and mine seep oils. Volumetric and hydrodynamic constraints make it highly improbable that such a small volume of 'dumped' oil could migrate over distances ranging from about 600 feet to 2.5 miles to the sites of the oil shows.

  13. Hydrocarbon seep-carbonates of a Miocene forearc (East Coast Basin), North Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Campbell, Kathleen A.; Francis, David A.; Collins, Mike; Gregory, Murray R.; Nelson, Campbell S.; Greinert, Jens; Aharon, Paul

    2008-02-01

    An ancient hydrocarbon seep province of 14 isolated, authigenic carbonate deposits has been identified in fine-grained, deep-marine siliciclastic strata of the Miocene East Coast Basin, North Island, New Zealand. These forearc sediments have been uplifted and complexly deformed into accretionary ridges, adjacent to the still-active Hikurangi convergent margin. Older active and passive margin strata (mid-Cretaceous to Oligocene in age) underlie the Neogene sequence, and contain oil- and gas-prone source rocks. Older Mesozoic meta-sedimentary rocks constitute the backstop against which the current phase of subduction-related sedimentation has accumulated (~ 24 Ma-present). The seep-carbonates (up to 10 m thick, 200 m across) archive methane signatures in their depleted carbon isotopes (to δ13C -51.7‰ PDB), and contain chemosynthesis-based paleocommunities (e.g. worm tubes, bathymodioline mussels, and vesicomyid, lucinid and thyasirid bivalves) typical of other Cenozoic and modern seeps. Northern and southern sites are geographically separated, and exhibit distinct lithological and faunal differences. Structural settings are variable. Seep-associated lithologies also are varied, and suggest carbonate development in sub-seafloor, seafloor and physically reworked (diapiric expansion, gas explosion, gravity slide or debris flow) settings, similar to Italian Apennine seep deposits of overlapping ages. Peculiar attributes of the New Zealand Miocene seep deposits are several, including digitate thrombolites of clotted microbial micrite encased in thick, isopachous horizons and botryoids of aragonite. Seep plumbing features are also well-exposed at some sites, displaying probable gas-explosion breccias filled with aragonite, tubular concretions (fluid conduits), and carbonate-cemented, thin sandstone beds and burrows within otherwise impermeable mudstones. A few seeps were large enough to develop talus-debris piles on their flanks, which were populated by lucinid bivalves

  14. Hydrocarbon gas seeps of the convergent Hikurangi margin, North Island, New Zealand

    USGS Publications Warehouse

    Kvenvolden, K.A.; Pettinga, J.R.

    1989-01-01

    Two hydrocarbon gas seeps, located about 13 km apart, have distinctive molecular and isotopic compositions. These seeps occur within separate tectonic melange units of narrow parallel trending and structurally complex zones with incorporated upper Cretaceous and Palaeogene passive continental margin deposits which are now compressively deformed and imbricated along the convergent Hikurangi margin of North Island, New Zealand. At Brookby Station within the Coastal High, the seeping hydrocarbon gas has a methane/ethane ratio of 48 and ??13C and ??D values of methane of -45.7 and -188???, respectively (relative to the PDB and SMOW standards). Within the complex core of the Elsthorpe Anticline at Campbell Station seep, gas has a methane/ethane ratio of about 12000, and the methane has ??13C and ??D values of -37.4 and -170???, respectively. The source of the gases cannot be positively identified, but the gases probably originate from the thermal decomposition of organic matter in tectonically disturbed upper Cretaceous and/or lower Tertiary sedimentary rocks of passive margin affinity and reach the surface by migration along thrust faults associated with tectonic melange. The geochemical differences between the two gases may result from differences in burial depths of similar source sediment. ?? 1989.

  15. Seep Carbonates From Tubeworm- and Mussel-Associated Environments at Atwater Valley, Northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Feng, D.; Roberts, H. H.; Chen, D.

    2008-12-01

    During 2006 and 2007, MMS and NOAA jointly supported cruises where fifteen hydrocarbon seep sites at greater than 1000 m water depth on the lower Louisiana slope in the Gulf of Mexico (GOM) were explored. These sites contain numerous authigenic carbonates as well as high-density communities of tubeworms and mussels. However, the integrated petrographic and geochemical characterization of the tubeworm- and mussel-associated carbonates remains poorly known. Here, a comparative study of petrographic and geochemical features of the carbonate samples from tubeworm- and mussel- associated environments was approached for an active and complex seep site at Atwater Valley lease block 340 (AT 340) at 2200 m water depth in the GOM. The carbonate morphologies include concretion, blocky and massive carbonates up to several meters in size, and irregularly shaped carbonates, some of them are displaying high porosity. Some are highly brecciaed with aragonite layers of varying thicknesses lining fractures and voids. Lithologically, the carbonates are microcrystalline Mg-calcite, calcite and aragonite containing peloids, clasts and shell fragments. The carbon isotopic composition of carbonates varies narrowly, ranging from -46.45 ‰ to - 60.81 ‰, indicating 13C-depleted carbon source probably methane of microbial origin. But the common trend is that the tubeworm-associated carbonates have more depleted δ13C values when compared to mussel-associated carbonates. A similarly small variability of δ18O values (+3.12 ‰ to +5.09 ‰) demonstrates the temperature and/or fluid composition did not change greatly during carbonate. The total content of rare earth elements (REE) of the 5% HNO3-treated solution of the carbonates is from 6.54 ppm to 29.41 ppm. The shale-normalized REE patterns show slightly positive Ce anomalies, suggests that the carbonates precipitated under anoxic conditions. The possible factors (i.e. habitat of chemosynthetic animals, depth of carbonate precipitation

  16. An evaluation of petrogenic hydrocarbons in northern Gulf of Alaska continental shelf sediments - The role of coastal oil seep inputs

    USGS Publications Warehouse

    Short, J.W.; Kolak, J.J.; Payne, J.R.; Van Kooten, G. K.

    2007-01-01

    We compared hydrocarbons in water, suspended particulate matter (SPM), and riparian sediment collected from coastal watersheds along the Yakataga foreland with corresponding hydrocarbons in Gulf of Alaska benthic sediments. This comparison allows an evaluation of hydrocarbon contributions to marine sediments from natural oil seeps, coal and organic matter (e.g., kerogen) associated with eroding siliciclastic rocks. The samples from oil seeps show extensive loss of low-molecular weight n-alkanes (hydrocarbon fingerprints on the SPM and riparian sediment samples collected upstream from the oil seeps. After entering the fluvial systems, hydrocarbons from seep oils are rapidly diluted, and associate with the SPM phase as oil-mineral-aggregates (OMA). Johnston Creek, the watershed containing the most prolific seep, conveys detectable seep-derived hydrocarbons to the Gulf of Alaska, but overall seep inputs are largely attenuated by the (non-seep) petrogenic hydrocarbon content of the high SPM loads. In contrast to the geochemical signature of seep oil, Gulf of Alaska benthic sediments are characterized by abundant alkylated naphthalene homologues, relatively smooth n-alkane envelopes (n-C9 through n-C34, but with elevated levels of n-C27, n-C29, and n-C31), and small UCMs. Further, hydrocarbons in benthic sediments are highly intercorrelated. Taken together, these characteristics indicate that seep oil is a negligible petrogenic hydrocarbon source to the Gulf of Alaska continental shelf. Coaly material separated from the benthic sediment samples using a dense liquid (???2.00 g cm-3) also accounted for a minor portion of the total PAH (1-6%) and total n-alkanes (0.4-2%) in the benthic samples. Most of the hydrocarbon burden in the sediments is found in the denser sediment fraction and likely derives from organic matter contributed by denudation of siliciclastic formations in

  17. Initial results of comparing cold-seep carbonates from mussel- and tubeworm-associated environments at Atwater Valley lease block 340, northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Feng, Dong; Roberts, Harry H.

    2010-11-01

    Chemosymbiotic macrofauna (such as mussels and tubeworms) and authigenic carbonates are typical of many hydrocarbon seeps. To address whether mussels and tubeworms could impact the sediment geochemistry of their habitat where authigenic carbonates are precipitated, a comparative study of petrographic and geochemical features of the authigenic carbonates from mussel- and tubeworm-associated environments at hydrocarbon seeps in Atwater Valley lease area block 340 (AT340) of the Gulf of Mexico was undertaken. Both mussel- and tubeworm-associated carbonates are dominated by high-magnesium calcite (HMC) and aragonite, and two tubeworm-associated carbonate samples have minor amounts of dolomite. The δ13C values of all carbonates are low, ranging from -60.8‰ to -35.5‰ PDB. Although there is much overlap, surprisingly the δ13C values of mussel-associated carbonates are generally higher than those of tubeworm-associated carbonates (-51.8‰ vs. -54.8‰ for an average of over 60 subsamples). It is suggested that (1) carbon isotopic vital effect of seep mussels and tubeworms, (2) fluid physical pumping of mussels, and (3) release of sulfate by tubeworm roots may be responsible for the relatively lower δ13C values of tubeworm-associated carbonates. It has been suggested that the heterogeneities in mineralogy and stable carbon isotope geochemistry of the seep carbonates may be attributed to the activity of macrofauna (mussels and tubeworms) and associated microbes. Our observations also suggest that at AT340 the geochemical evolution of seep macrofauna is from a mussel-dominated environment to a mixed mussel-tubeworm environment, and finally to a mostly tubeworm-dominated environment. This evolution is controlled mainly by the habitat, e.g., hydrocarbon seep flux.

  18. Epizooic metazoan meiobenthos associated with tubeworm and mussel aggregations from cold seeps of the northern Gulf of Mexico

    PubMed Central

    Bright, M.; Plum, C.; Riavitz, L.A.; Nikolov, N.; Martinez Arbizu, P.; Cordes, E.E.; Gollner, S.

    2010-01-01

    The abundance and higher taxonomic composition of epizooic metazoan meiobenthic communities associated with mussel and tubeworm aggregations of hydrocarbon seeps at Green Canyon, Atwater Valley, and Alaminos Canyon in depths between 1400 and 2800 m were studied and compared to the infaunal community of non-seep sediments nearby. Epizooic meiofaunal abundances of associated meiobenthos living in tubeworm bushes and mussel beds at seeps were extremely low (usually <100 ind. 10 cm−2), similar to epizooic meiofauna at deep-sea hydrothermal vents, and the communities were composed primarily of nematodes, copepods, ostracods, and halacarids. In contrast, epizooic meiobenthic abundance is lower than previous studies have reported for infauna from seep sediments. Interestingly, non-seep sediments contained higher abundances and higher taxonomic diversity than epizooic seep communities, although in situ primary production is restricted to seeps. PMID:21264038

  19. Epizooic metazoan meiobenthos associated with tubeworm and mussel aggregations from cold seeps of the northern Gulf of Mexico.

    PubMed

    Bright, M; Plum, C; Riavitz, L A; Nikolov, N; Martinez Arbizu, P; Cordes, E E; Gollner, S

    2010-11-01

    The abundance and higher taxonomic composition of epizooic metazoan meiobenthic communities associated with mussel and tubeworm aggregations of hydrocarbon seeps at Green Canyon, Atwater Valley, and Alaminos Canyon in depths between 1400 and 2800 m were studied and compared to the infaunal community of non-seep sediments nearby. Epizooic meiofaunal abundances of associated meiobenthos living in tubeworm bushes and mussel beds at seeps were extremely low (usually <100 ind. 10 cm(-2)), similar to epizooic meiofauna at deep-sea hydrothermal vents, and the communities were composed primarily of nematodes, copepods, ostracods, and halacarids. In contrast, epizooic meiobenthic abundance is lower than previous studies have reported for infauna from seep sediments. Interestingly, non-seep sediments contained higher abundances and higher taxonomic diversity than epizooic seep communities, although in situ primary production is restricted to seeps. PMID:21264038

  20. Deep-sea hydrocarbon seep communities: evidence for energy and nutritional carbon sources

    SciTech Connect

    Brooks, J.M.; Kennicutt, M.C. II; Fisher, C.R.; Macko, S.A.; Cole, K.; Childress, J.J.; Bidigare, R.R.; Vetter, R.D.

    1987-11-20

    Mussels, clams, and tube worms collected in the vicinity of hydrocarbon seeps on the Louisiana slope contain mostly dead carbon, indicating that dietary carbon is largely derived from seeping oil and gas. Enzyme assays, elemental sulfur analysis, and carbon dioxide fixation studies demonstrate that vestimentiferan tube worms and three clam species contain intracellular, autotrophic sulfur bacterial symbionts. Carbon isotopic ratios of 246 individual animal tissues were used to differentiate heterotrophic (delta/sup 14/C = -14 to -20 per mil), sulfur-based (delta/sup 14/C = -30 to -42 per mil), and methane-based (delta/sup 13/C = <-40 per mil) energy sources. Mussels with symbiotic methanotrophic bacteria reflect the carbon isotopic composition of the methane source. Isotopically light nitrogen and sulfur confirm the chemoautotrophic nature of the seep animals. Sulfur-based chemosynthetic animals contain isotopically light sulfur, whereas methane-based symbiotic mussels more closely reflect the heavier oceanic sulfate pool. The nitrogen requirement of some seep animals may be supported by nitrogen-fixing bacteria. Some grazing neogastropods have isotopic values characteristic of chemosynthetic animals, suggesting the transfer of carbon into the background deep-sea fauna.

  1. Deep-water hydrocarbon seeps in Guaymas Basin, Gulf of California

    USGS Publications Warehouse

    Simoneit, B.R.T.; Lonsdale, P.F.; Edmond, J.M.; Shanks, Wayne C., III

    1990-01-01

    Acoustically discovered hydrocarbon seeps along a transform fault zone on the Sonoran margin of Guaymas Basin and in the Southern Trough of Guaymas Basin were examined and sampled during dives of DSV Alvin. Seepage of methane and heavier hydrocarbons occurs through shallow pockmarks along the eroding crest of a steep anticline, 1600 m below sea level. Extensive ledges of aragonite crop out around the rims of the pockmarks; isotopic analysis indicates that carbonate precipitation is a result of methane oxidation. Seepage zones within the pockmarks support dense communities of Calyptogena, half buried in the mud; tubeworms (Lamellibracheae sp.) have colonized many of the aragonite outcrops. Though the margin site is only a few kilometers from a high-temperature sulfide-precipitating and petroleum-discharging vent system at a nearby center, its structural setting is more akin to pockmarks described from continental shelves, and its chemosynthetic fauna is more like that around low temperature seeps on other continental slopes and margins (e.g. Oregon, U.S.A., and Japan). The seep in the Southern Trough is a condensate-type petroleum (C1-C40) and rises as a plume from a young vent-mound system about 2000 m below sea level. ?? 1990.

  2. Geochemical Tracers and Rates of Short-Chain Alkane Production in Gulf of Mexico Cold Seep Sediments

    NASA Astrophysics Data System (ADS)

    Sibert, R.; Bernard, B. B.; Brooks, J. M.; Hunter, K.; Joye, S. B.

    2014-12-01

    The organic-rich cold seep sediments in the deep Gulf of Mexico commonly contain mixtures of light hydrocarbon gases either dissolved in pore fluids, adsorbed to sediment particles, trapped in methane ice, or as free gas. The dominant component in these natural gas mixtures is typically methane (C1), but ethane (C2) and propane (C3) are nearly always present in trace or major amounts. The ratio of C1:C2:C3 varies but C2 and C3 are typically present at single digit percent levels, whereas methane usually dominates at >80%. Methane production proceeds by at least two well-studied mechanisms: either 1) by thermocatalytic cracking of fossil organic matter, or 2) as a direct product of microbial metabolism, methanogenesis. In contrast, ethane and propane production in deep-sea sediments has been historically attributed only to thermocatalytic processes. However, limited data suggests production of C2/C3 compounds through the activity of archaea. Such studies of microbial- driven dynamics of C2/C3 gases (i.e. 'alkanogenesis') in cold seep sediments are rare. Furthermore, the identities of potential substrates are poorly constrained and no attempt has been made to quantify production rates of C2/C3 gases. However, carbon isotopic data on ethane and propane from deep cores from the Gulf of Mexico suggest alkanogenesis at depth in the sediment column and alkane oxidation in uppermost oxidant-rich sediments. Here, we present the results of a series of incubation experiments using sediment slurries culled from GC600, one of the most prolific natural oil and gas seeps in the Gulf of Mexico. Rates of both alkane production and oxidation were measured under a variety of conditions to assess the net rates of alkane production and elucidate the driving microbiological mechanisms and controls on the central processes of >C1 alkane cycling in cold seep sediments. Microbial processes are important both in terms of alkane production and oxidation, raising many questions as to the

  3. Jurassic hydrocarbon seep-carbonates in the High Atlas Basin (Morocco)

    NASA Astrophysics Data System (ADS)

    Bodin, Stephane; Kothe, Tim; Rose, Johannes; Krencker, Francois-Nicolas; Kabiri, Lahcen

    2015-04-01

    In the central High Atlas Basin of Morocco, the occurrence of Jurassic hydrocarbon seeps is observed in two distinct horizons: (1) the uppermost Polymorphum ammonite zone (Lower Toarcian) and (2) the Sauzei (eq. Propiquans) ammonite zone (Lower Bajocian). The Toarcian seep-carbonates are made of 5 - 6cm in diameter, half-spherical concretions that surround two vertical and closely spaced tubes, parallel to each other. Each tube is less than 1cm in diameter and filled with late diagenetic cements. The tubes are interpreted as burrow trace fossil. The concretions are embedded within an organic-matter rich interval and resemble to the Tisoa siphonalis concretions described in the upper Pliensbachian of Western Europe. Carbon isotope values decrease from the rim to the center of the concretion (from 1 to -7 per mil) whereas oxygen isotope values remain stable around -7 per mil. The C-isotope values of the concretion rim are similar to the bulk carbon isotope values of the embedding rocks. The most negative C-isotope values indicate that the carbon source of the carbonate precipitated in the centre of the concretion is likely sourced from the organoclastic sulfate reduction zone. The Bajocian seep-carbonates are observed within the dark calcareous mudstone of the Sauzei zone. One peculiarly well-exposed seep system shows the presence of a plumbing system leading to a 20cm thick carbonate crust showing the occasional occurrence of chimney structures on its upper part. The high abundance of serpulids clusters within the carbonate crust shows that it was precipitated at the water-sediment interface. The pipe structures of the plumbing system are composed of an external micritic rim enclosing a central tube that can be up to 12cm large. A complex, multi-phased infilling is observed in the inner part of the pipe and separated from the rim by a millimetric pyritized crust. Carbon isotope values are comprised between -20 per mil and -8 per mil for the micritic rim, whereas the

  4. Escarpment seeps at Shiprock, New Mexico. [Risk posed by seep water to human health and the environment

    SciTech Connect

    Not Available

    1991-10-01

    The purpose of this report is to characterize the seeps identified at the Shiprock UMTRA Project site during the prelicensing custodial care inspection conducted in December of 1990, to evaluate the relationship between the seeps and uranium processing activities or tailings disposal, and to evaluate the risk posed by the seep water to human health and the environment. The report provides a brief description of the geology, groundwater hydrology, and surface water hydrology. The locations of the seeps and monitor wells are identified, and the water quality of the seeps and groundwater is discussed in the context of past activities at the site. The water quality records for the site are presented in tables and appendices; this information was used in the risk assessment of seep water.

  5. Food-web structure of seep sediment macrobenthos from the Gulf of Mexico

    USGS Publications Warehouse

    Demopoulos, Amanda W.J.; Gualtieri, Daniel; Kovacs, Kaitlin

    2010-01-01

    The slope environment of the Gulf of Mexico (GOM) supports dense communities of seep megafaunal invertebrates that rely on endosymbiotic bacteria for nutrition. Seep sediments also contain smaller macrofaunal invertebrates whose nutritional pathways are not well understood. Using stable-isotope analysis, we investigate the utilization of chemosynthetically fixed and methane-derived organic matter by macrofauna. Biological sampling was conducted in three lower-slope GOM seep environs: Green Canyon (GC852, 1428 m), Atwater Valley (AT340, 2230 m), and Alaminos Canyon (AC601, 2384 m). Infaunal delta13C and delta15N exhibited a broad range of values; most infauna appeared to be heterotrophic, although several taxa had very light delta15N and delta13C values, indicating possible reliance on chemoautotrophic symbioses. The lightest delta13C and delta15N values were observed in nematodes (delta13C=-54.6 + or - 0.1 per mil, delta15N=-6.1 + or - 0.2 per mil) and one gastropod (delta13C=-54.1 per mil, delta15N=-1.1 per mil) from Green Canyon. Mixing-model results indicated that sulfur-oxidizing Beggiatoa may be an important food source for seep infauna; the rate of utilization ranged from 60% to 100% at Green Canyon and Atwater Valley. The overall range in isotope values was similar across the three sites, suggesting that biogeochemical processes may be very similar in these geographically distinct areas.

  6. Food-web structure of seep sediment macrobenthos from the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Demopoulos, Amanda W. J.; Gualtieri, Daniel; Kovacs, Kaitlin

    2010-11-01

    The slope environment of the Gulf of Mexico (GOM) supports dense communities of seep megafaunal invertebrates that rely on endosymbiotic bacteria for nutrition. Seep sediments also contain smaller macrofaunal invertebrates whose nutritional pathways are not well understood. Using stable-isotope analysis, we investigate the utilization of chemosynthetically fixed and methane-derived organic matter by macrofauna. Biological sampling was conducted in three lower-slope GOM seep environs: Green Canyon (GC852, 1428 m), Atwater Valley (AT340, 2230 m), and Alaminos Canyon (AC601, 2384 m). Infaunal δ13C and δ15N exhibited a broad range of values; most infauna appeared to be heterotrophic, although several taxa had very light δ15N and δ13C values, indicating possible reliance on chemoautotrophic symbioses. The lightest δ13C and δ15N values were observed in nematodes (δ13C=-54.6±0.1‰, δ15N=-6.1±0.2‰) and one gastropod (δ13C=-54.1‰, δ15N=-1.1‰) from Green Canyon. Mixing-model results indicated that sulfur-oxidizing Beggiatoa may be an important food source for seep infauna; the rate of utilization ranged from 60% to 100% at Green Canyon and Atwater Valley. The overall range in isotope values was similar across the three sites, suggesting that biogeochemical processes may be very similar in these geographically distinct areas.

  7. Temperature-Dependent Variations in Sulfate-Reducing Communities Associated with a Terrestrial Hydrocarbon Seep

    PubMed Central

    Cheng, Ting-Wen; Lin, Li-Hung; Lin, Yue-Ting; Song, Sheng-Rong; Wang, Pei-Ling

    2014-01-01

    Terrestrial hydrocarbon seeps are an important source of naturally emitted methane over geological time. The exact community compositions responsible for carbon cycling beneath these surface features remain obscure. As sulfate reduction represents an essential process for anoxic organic mineralization, this study collected muddy fluids from a high-temperature hydrocarbon seep in Taiwan and analyzed community structures of sulfate-supplemented sediment slurries incubated anoxically at elevated temperatures. The results obtained demonstrated that sulfate consumption occurred between 40°C and 80°C. Dominant potential sulfate reducers included Desulfovibrio spp., Desulfonatronum spp., Desulforhabdus spp., and Desulfotomaculum spp. at 40°C, Thermodesulfovibrio spp. at 50°C, Thermodesulfovibrio spp. and Thermacetogenium spp. at 60°C, Thermacetogenium spp. and Archaeoglobus spp. at 70°C, and Archaeoglobus spp. at 80°C. None of these potential sulfate reducers exceeded 7% of the community in the untreated sample. Since no exogenous electron donor was provided during incubation, these sulfate reducers appeared to rely on the degradation of organic matter inherited from porewater and sediments. Aqueous chemistry indicated that fluids discharged in the region represented a mixture of saline formation water and low-salinity surface water; therefore, these lines of evidence suggest that deeply-sourced, thermophilic and surface-input, mesophilic sulfate-reducing populations entrapped along the subsurface fluid transport could respond rapidly once the ambient temperature is adjusted to a range close to their individual optima. PMID:25273230

  8. Isolation and Characterization of Ethane, Propane, and Butane Consuming Bacteria from Marine Hydrocarbon Seeps

    NASA Astrophysics Data System (ADS)

    Redmond, M. C.; Valentine, D. L.

    2005-12-01

    Three strains of ethane, propane, or butane consuming bacteria were isolated from marine hydrocarbon seep sediments at Coal Oil Point, off shore Santa Barbara, CA. These three isolates (MR1, MR2 and MR3) were capable of growth at natural environmental temperatures and salinity. Isolate MR2 was capable of growth on ethane or propane as the sole carbon source, isolate MR4 on propane or butane, and isolate MR3 on ethane, propane, or butane. All three isolates were also able to grow on other carbon-containing molecules, including ethanol, 1-propanol, 2-propanol, acetate, butyrate, sucrose, and dextrose, and isolates MR3 and MR4 were able to grow on 1-butanol and 2-butanol. None showed significant growth with methane, methanol, or formate as the sole carbon source. 16S rDNA sequencing indicated that isolate MR2 was most closely related to the gamma-Proteobacterium Pseudomonas stutzeri, while isolates MR3 and MR4 were both Gram-positive and most similar to Rhodococcus wratislaviensis and Rhodococcus opacus, respectively. Compared to methanotrophs, relatively little is known about the organisms that consume the C2-C4 alkanes, but both our isolates and the previously described species appear to be capable of metabolizing a wide variety of carbon compounds, including several common pollutants. The growth of these hydrocarbon-oxidizing bacteria on other organic compounds raises the possibility that the abundance and distribution of organic matter might be expected to impact the oxidation of C2-C4 hydrocarbons. Additional studies will further characterize the range of metabolism, and will investigate the importance of these organisms in natural hydrocarbon seep environments.

  9. Identification of Methane, Ethane, and Propane Oxidizing Bacteria at Marine Hydrocarbon Seeps by Stable Isotope Probing

    NASA Astrophysics Data System (ADS)

    Redmond, M.; Ding, H.; Friedrich, M. W.; Valentine, D. L.

    2008-12-01

    Hydrocarbon seeps emit substantial amounts of oil and natural gas into the marine environment, where they can be oxidized by microorganisms in the sediment and water column. Here, we used stable isotope probing of DNA and lipid biomarkers to identify the microorganisms actively consuming 13C-labeled natural gas compounds in seep sediment samples. Surface sediment was collected from the Coal Oil Point seep field (offshore Santa Barbara, California, USA) and incubated under aerobic conditions with 13C labeled methane, ethane, or propane for up to 37 days, with sediment sub-samples taken at 3-4 intermediate time points. DNA was extracted from sediment and separated by CsCl density gradient centrifugation. The microbial community in each fraction was profiled using T-RFLP, and bacterial 16S rRNA gene clone libraries were constructed from un-incubated hydrocarbon seep sediment and selected isotopically 'heavy' (13C) and 'light' (12C) gradient fractions from ethane incubations. All clone libraries were dominated by sequences from members of the family Rhodobacteraceae (>25% of sequences) and a diverse group of Gammaproteobacteria, including sequences related to those of methylotrophs and to those of bacteria known to consume the longer-chain alkanes present in crude oil. After 14 days of incubation, the relative abundance of Rhodobacteraceae was higher in 'heavy' fractions from the 13C-ethane incubation than in 'light' fractions, suggesting incorporation of 13C label. The Rhodobacteraceae are very diverse metabolically, but have often been observed in abundance in oil contaminated seawater. Several members of this group have been shown to oxidize longer chain alkanes (C10 or higher), but none have been previously linked to the consumption of the gaseous alkanes ethane, propane, and butane. For the final time point, 13C content of phospholipid fatty acids (PLFA) were also analyzed, showing substantial incorporation of 13C over 37 days. In the methane incubation

  10. Spatial and temporal characterization of a cold seep-hydrate system (Woolsey Mound, deep-water Gulf of Mexico)

    NASA Astrophysics Data System (ADS)

    Simonetti, Antonello

    Cold seeps are areas where methane is transferred from the lithosphere into the hydrosphere, accounting for the major source of hydrocarbons in seawaters. Formation of gas hydrate in cold seeps modulates the global discharge of methane to the environment. However, cold seeps are dynamic settings where hydrates dissociate on short and long time-scales triggering substantial methane fluxes to the oceans. These methane vents sustain unique ecosystems at the ocean floors and contribute to ocean acidification. Also, the methane can potentially reach the sea surface and be exchanged with the atmosphere contributing to global warming. Understanding how cold seep-hydrate systems (CSHSs) operate through time and space is therefore crucial to evaluate their global impact on ocean biogeochemistry and climate. The area investigated is Woolsey Mound, a CSHS located in the Northern Gulf of Mexico. For the first part of the research, the goal was to determine the spatial distribution of subsurface gas hydrate at this site. In terms of hydrate-reservoir category, Woolsey Mound is classified as "seafloor mound" and "fractured mud". To date, these two categories are poorly constrained worldwide. This study documents a successful integration of high-resolution seismic and core data to detect the spatial distribution of hydrates in such settings. The approach adopted and the model may be applied globally for these reservoir categories. The aim of the second part was to untangle the contentious long-term (thousands to millions of years) dynamics driving methane hydrate dissociation and seepage in CSHSs. Analyses on high-resolution seismic data suggest that tectonics is the main forcing mechanism and that CSHSs may operate independently from eustatic fluctuations. This contradicts the broad consensus in the literature about methane seepage in CSHSs being systematically triggered during sea-level lowstand. The third part of the research aimed to characterize the short-term (years

  11. In-situ and on-line measurement of gas flux at a hydrocarbon seep from the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Di, Pengfei; Feng, Dong; Chen, Duofu

    2014-06-01

    Natural hydrocarbon seeps in the marine environment are important sources of methane and other greenhouse gases to the ocean and the atmosphere. Accurate quantification of methane flux at hydrocarbon seeps is therefore necessary to evaluate their influence on the global methane budget and climate change. Hydrocarbon seeps on the seabed produce a near-shore gas bubble zone along the shallow western coast of Hainan Island, northern South China Sea. An in-situ and on-line gas flux measuring device was deployed over a hydrocarbon seep to quantify the gas flux by equal volume exchange venting from the seabed offshore of Ledong Town, Hainan Island, over 19 days. The physiochemical parameters and the dissolved methane concentration of the bottom water at the hydrocarbon seep were also measured. The gas flux from the hydrocarbon seep varied from 22 to 77 l/day with the tidal period and was strongly negatively correlated with water depth. The flux data from the seep suggests that the variation in hydrostatic pressure induced by tidal forcing and ocean swell may control the variation of the gas flux. The bottom water dissolved methane concentration, ranging from 26 to 74 nmol/L, was negatively correlated with temperature and water depth at the seabed and positively with the gas flux. The total gas volume released from the hydrocarbon seep was 30.5 m3 for the 19-day period, providing an estimated gas flux of 600 m3/yr. The 120 known hydrocarbon seeps along the eastern edge of the Yinggehai Basin could vent a large quantity of methane from the seafloor, which suggests that hydrocarbon seeps on the continental margin of the northern South China Sea may be an important natural source of methane to the atmosphere.

  12. C/sup 13/-depleted authigenic carbonate buildups from hydrocarbon seeps, Louisiana Continental Slope

    SciTech Connect

    Roberts, H.H.; Sassen, R.; Aharon, P.; Carney, R.

    1989-03-01

    Geohazard and geochemical survey data consisting of high-resolution profiles, side-scale sonographs, drop cores, dredge samples, and borings have substantiated the consistent association between carbonate buildups and hydrocarbon seeps on the Louisiana continental slope. Analyses indicate a range of carbonate mineralogies including aragonite, Mg-calcite, and dolomite that are extremely depleted in the C/sup 13/ isotope (/approximately/dC/sup 13/ values to /minus/48/per thousand/ PDB). Microbial oxidation of methane (biogenic and thermogenic) and crude oil creates a source of pore water CO/sub 2/ containing isotopically light carbon, which triggers carbonate precipitation. Geophysical and geochemical evidence suggests that both surface and subsurface lithification is taking place. Recent observations and samples collected using a Pisces class research submersible confirm the abundance of C/sup 13/-depleted sedimentary carbonates and massive authigenic buildups associated with the tops and flanks of shallow salt diapirs and gas hydrate hills. Although chemosynthetic communities (including tube worms and bivalves) with isotopically light carbon in tissues have been described from gas seeps, bacterial mats sampled from several seep areas using a submersible have /delta/C/sup 13/ values of /minus/28 to /minus/ /per thousand/ PDB, suggesting a crude oil contribution to microbial biomass. Lithoherms 15 m in vertical dimension are not unusual on dome crests. These features dominate mesoscale sea-floor topography on the slope and have important short-term impacts on platform locations as well as pipeline routing. They are of long-term importance as sites for low sea level reefs. Moreover, these observations provide new insight into the earliest stages of salt-dome cap-rock evolution.

  13. Community composition and temporal change at deep Gulf of Mexico cold seeps

    NASA Astrophysics Data System (ADS)

    Lessard-Pilon, Stephanie; Porter, Matthew D.; Cordes, Erik E.; MacDonald, Ian; Fisher, Charles R.

    2010-11-01

    Specialized cold-seep communities have been known to exist in the Gulf of Mexico (GOM) since the mid-1980s, but only recently has extensive research been carried out on sites at depths >1000 m. This study uses a combination of imagery and analyses within a Geographic Information Systems (GIS) framework to examine the composition of mussel and tubeworm communities at depths between 2200 and 2800 m in the Gulf of Mexico, spatial relations among the fauna, and changes in these communities over time. Photomosaics at three discrete seep communities were obtained in 2006 and a video mosaic of another community was obtained in 1992. Each of these communities was re-imaged in 2007. In addition, quantitative physical collections were made within two of the photomosaic sites and used to confirm the identification of megafauna, quantify the occurrence of smaller and cryptic macrofauna, and allow first-order calculations of biomass within the sites. Substrate type had a significant effect on community composition. Significant associations were identified between live mussels with anemones, shrimp, and sea cucumbers, and between tubeworm aggregations and Munidopsis sp. crabs and encrusting fauna, indicating differences in the composition of megafauna associated with adjacent mussel and tubeworm aggregations. Little change was seen in the total area colonized by foundation fauna (tubeworms and mussels) between years at any site. However, significant changes occurred in the positions of mussels, even over periods of a single year, at all sites, and evidence for the establishment of new tubeworm aggregations between 1992 and 2007 was noted at one site. These photomosaics provide data suggesting that environmental conditions can change over small spatial and temporal scales and mussels move in response to these changes. The successional trends are examined and compared to the patterns that have been documented in shallow (<1000-m depth) Gulf of Mexico seep communities.

  14. Stable isotopes provide new insights into vestimentiferan physiological ecology at Gulf of Mexico cold seeps

    NASA Astrophysics Data System (ADS)

    Becker, Erin Leigh; Macko, Stephen A.; Lee, Raymond W.; Fisher, Charles R.

    2011-02-01

    On the otherwise low-biomass seafloor of the Gulf of Mexico (GoM) continental slope, natural oil and gas seeps are oases of local primary production that support lush animal communities. Hundreds of seep communities have been documented on the continental slope, and nutrition derived from seeps could be an important link in the overall GoM food web. Here, we present a uniquely large and cohesive data set of δ13C, δ15N, and δ34S compositions of the vestimentiferan tubeworms Escarpia laminata and Lamellibrachia sp. 1, which dominate biomass at GoM seeps and provide habitat for hundreds of other species. Our sampling design encompassed an entire region of the GoM lower slope, allowing us for the first time to assess spatial variability in isotope compositions and to robustly address long-standing hypotheses about how vestimentiferans acquire and cycle nutrients over their long lifespan (200+ years). Tissue δ13C values provided strong evidence that larger adult vestimentiferans use their buried roots to take up dissolved inorganic carbon from sediment pore water, while very small individuals use their plume to take up carbon dioxide from the seawater. δ34S values were extremely variable among individuals of the same species within one location (<1 m2 area), indicating high variability in the inorganic sulfur pools on a very small spatial scale. This finding supports the hypothesis that vestimentiferans use their roots to cycle sulfate and sulfide between their symbionts and free-living consortia of sulfate-reducing archaea in the sediment. Finally, consistent differences in δ15N between two cooccurring vestimentiferan species provided the first strong evidence for partitioning of inorganic resources, which has significant implications for the ecology and evolution of this taxonomic group.

  15. New records and a new species of bivalve (Mollusca: Bivalvia) from Miocene hydrocarbon seep deposits, North Island, New Zealand.

    PubMed

    Saether, Kristian P; Jingeng, Sha; Little, Crispin T S; Campbell, Kathleen A

    2016-01-01

    Fourteen bivalve taxa belonging to 11 families are present in at least 13 early to middle Miocene hydrocarbon seep deposits in the East Coast Basin, North Island, New Zealand. Among these are at least three new species, one of which, Semeloidea (s. l.) bexhavenensis sp. nov. (Lasaeidae), is described here. New distribution data are recorded for bivalve species in the families Limidae, Propeamussiidae, Malleidae and Solemyidae. Additional morphological details of Gigantidas coseli (Mytilidae) and Pratulum quinarium (Cardiidae) are provided based upon previously unrecorded internal shell features. Palaeoecological analysis indicates that bivalves utilized a broad range of modes of life and niches within the New Zealand Miocene seep environment, and no more than ca. 30% of these bivalve species were likely to have been obligate to seeps. PMID:27615822

  16. Benthic Community Structure and Sediment Geochemical Properties at Hydrocarbon Seeps Along the Continental Slope of the Western North Atlantic

    NASA Astrophysics Data System (ADS)

    Demopoulos, A. W.; Bourque, J. R.; Brooke, S.

    2015-12-01

    Hydrocarbon seeps support distinct benthic communities capable of utilizing reduced chemical compounds for nutrition. In recent years, methane seepage has been increasingly documented along the continental slope of the U.S. Atlantic margin. In 2012 and 2013, two seeps were investigated in this region: a shallow site near Baltimore Canyon (410-450 m) and a deep site near Norfolk Canyon (1600 m). Both sites contain extensive mussel beds and microbial mats. Sediment cores and grab samples were collected to quantify the abundance, diversity, and community structure of benthic macrofauna (>300 mm) in relationship to the associated sediment environment (organic carbon and nitrogen, stable isotopes 13C and 15N, grain size, and depth) of mussel beds, mats, and slope habitats. Macrofaunal densities in microbial mats were four times greater than those present in mussel beds and slope sediments. Macrofaunal communities were distinctly different both between depths and among habitat types. Specifically, microbial mat sediments were dominated by the annelid families Dorvilleidae, Capitellidae, and Tubificidae, while mussel habitats had higher proportions of crustaceans. Diversity was lower in Baltimore microbial mat habitats, but higher in mussel and slope sediments compared to Norfolk seep habitats found at deeper depths. Multivariate statistical analysis identified sediment carbon:nitrogen (C:N) ratios and 13C values as important variables for structuring the macrofaunal communities. Higher C:N ratios were present within microbial mat habitats and depleted 13C values occurred in sediments adjacent to mussel beds found in Norfolk Canyon seeps. Differences in the quality and source of organic matter present in the seep habitats are known to be important drivers in macrofaunal community structure and associated food webs. The multivariate analysis provides new insight into the relative importance of the seep sediment quality in supporting dense macrofaunal communities compared

  17. Enumeration of viruses and prokaryotes in deep-sea sediments and cold seeps of the Gulf of Mexico

    USGS Publications Warehouse

    Kellogg, Christina A.

    2010-01-01

    Little is known about the distribution and abundance of viruses in deep-sea cold-seep environments. Like hydrothermal vents, seeps support communities of macrofauna that are sustained by chemosynthetic bacteria. Sediments close to these communities are hypothesized to be more microbiologically active and therefore to host higher numbers of viruses than non-seep areas. Push cores were taken at five types of Gulf of Mexico habitats at water depths below 1000 m using a remotely operated vehicle (ROV). The habitats included non-seep reference sediment, brine seeps, a microbial mat, an urchin field, and a pogonophoran worm community. Samples were processed immediately for enumeration of viruses and prokaryotes without the addition of a preservative. Prokaryote counts were an order of magnitude lower in sediments directly in contact with macrofauna (urchins, pogonophorans) compared to all other samples (107 vs. 108 cells g-1 dry weight) and were highest in areas of elevated salinity (brine seeps). Viral-Like Particle (VLP) counts were lowest in the reference sediments and pogonophoran cores (108 VLP g-1 dry wt), higher in brine seeps (109 VLP g-1 dry wt), and highest in the microbial mats (1010 VLP g-1 dry wt). Virus-prokaryote ratios (VPR) ranged from <5 in the reference sediment to >30 in the microbial mats and >60 in the urchin field. VLP counts and VPR were all significantly greater than those reported from sediments in the deep Mediterranean Sea and in most cases were higher than recent data from a cold-seep site near Japan. The high VPR suggest that greater microbial activity in or near cold-seep environments results in greater viral production and therefore higher numbers of viruses.

  18. Evidence of the aryl hydrocarbon receptor in chemosynthetic mussels from the Gulf of Mexico

    SciTech Connect

    Willett, K.; Thomsen, J.; Wilson, C.; McDonald, S.; Safe, S.

    1995-12-31

    The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that controls expression of various genes including cytochrome P450. Polynuclear aromatic and halogenated aromatic hydrocarbons are agonists for the AhR in fish and mammalian species. Previously, a homologous AhR has not been identified in marine invertebrate species. Chemosynthetic mussels were collected from gas and petroleum seeps in the Gulf of Mexico to investigate the presence of the AhR and the induction of the cytochrome P450 system. Aryl hydrocarbon hydroxylase and glutathione S-transferase activities in the gill and hepatopancreas were elevated in the petroleum seep mussels relative to those from the gas seep. A nuclear AhR in the hepatopancreas was detected in both mussel populations after treatment with [{sup 3}H]-tetrachlorodibenzo-p-dioxin (tcdd) followed by sucrose density gradient analysis. Gel mobility shift assays using a labeled dioxin responsive element (DRE) oligonucleotide and tcdd-transformed mussel cytosol showed a retarded band which could be competed with excess unlabeled DRE. Results from gel shifts indicated specific binding of the tcdd-mussel AhR complex to its responsible element. Finally, PCR primers designed to amplify a 700 base pair region of the human AhR detected AhR mRNA in both mussel populations. The sequence of this PCR product is being determined. The presence of the AhR in marine invertebrates has important implications in the evolutionary age of the AhR.

  19. Reconnaissance Strategy for Seep Chemosynthetic Communities in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    MacDonald, I. R.; Roberts, H. H.; Fisher, C. R.; Bernard, B. B.; Joye, S.; Carney, R.; Hunt, J.; Shedd, W.

    2007-05-01

    The Continental Slope of the Gulf of Mexico hosts diverse chemosynthetic communities at oil and gas seeps. Exploration is needed to extend knowledge of the Gulf of Mexico chemosynthetic ecosystem in the zones anticipated to receive energy exploration and production activities over the coming decades. A nested survey approach can be used to identify representative sampling sites within this vast offshore area. Potential sites where chemosynthetic community could occur are selected on the basis geophysical, geochemical, and satellite remote-sensing indicators. Photo-reconnaissance using cost-effective camera systems is then used to confirm the presences or absence of chemosynthetic communities at high-probability sites. Follow-up sampling can then proceed with submersibles or ROVs to acquire tissue and or geochemical samples. However, because access is limited, submersible dives may not be possible at all sites. Two examples of this approach have recently been applied in the northern and southern Gulf of Mexico, respectively. We compared community characterizations obtained from the initial reconnaissance with more detailed characterizations forthcoming from submersible sampling. Our results show that major differences in community type and geochemical substrata are evident from preliminary reconnaissance, while details of animal densities and species compositions require targeted sampling with submersibles. However, given the limited access to submersibles, cost-effective surveys with deep-sea camera systems would greatly expand understanding of the zoogeography of chemosynthetic fauna in the Gulf of Mexico and Caribbean Sea.

  20. Natural hydrocarbon seepage on the continental slope to the east of Mississippi Canyon in the northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Rahman Talukder, Asrarur; Ross, Andrew; Crooke, Emma; Stalvies, Charlotte; Trefry, Christine; Qi, Xiubin; Fuentes, David; Armand, Stephane; Revill, Andrew

    2013-06-01

    5 June to 15 September 2010, a multidisciplinary marine survey was undertaken onboard the M/V Ryan Chouest in the region of the BP Deepwater Horizon incident site in the Gulf of Mexico. The primary objective of the survey was the continuous monitoring of hydrocarbon abundance from sea surface down to a maximum depth of 120 m. Compound abundances were inferred using a hydrocarbon sensor array with associated vertical cast system. In order to better understand the potential inputs from natural seepage in the vicinity of the spill, a Simrad EK60 high-resolution split beam echo sounder, operated at 38 kHz, was included in the survey between 7 July and 15 September 2010. During this period, three fields of natural seeps characterized by hydroacoustic flares were studied in detail. These seep fields are at water depths of approximately 430 m, 880 m, and 1370 m. They are associated with extensive cold seep systems. In particular, the area around Seep Field 1 (the vicinity of Deepwater Horizon) seems to present a vast area of active natural seepages in the Gulf of Mexico. The repeat surveys at two of the fields suggested that the cold seep systems here were active, with expulsions of hydrocarbons into the water column, at least during the periods of our acoustic surveys. Multiple lines of evidence gathered during the survey indicated that the observed hydroacoustic flares at the three fields identified consisted of oily bubble streams of gases of thermogenic origin. However, direct observation and sampling are required to reveal the precise nature of the flares. In the deep water Gulf of Mexico, the formation of a hydrate rim around bubbles seems to be a very important mechanism for the long transport of methane and oil in the water column.

  1. New gastropods from deep-sea hydrocarbon seeps off West Africa

    NASA Astrophysics Data System (ADS)

    Warén, Anders; Bouchet, Philippe

    2009-12-01

    Thirteen new species of gastropods are described from the Zairov 1-2 and Biozaire 1-3 cruises to the methane seeps off the Congo River: Patellogastropoda: Paralepetopsis sasakii sp. nov. (Neolepetopsidae); Cocculiniformia: Pyropelta oluae sp. nov. and P. sibuetae sp. nov. (Pyropeltidae); Tentaoculus granulatus sp. nov. (Pseudococculinidae); Neomphalina: Leptogyra costellata sp. nov. (Family uncertain); Vetigastropoda: Puncturella similis sp. nov. (Fissurellidae); Lepetodrilus shannonae sp. nov. (Lepetodrilidae); Caenogastropoda: Provanna reticulata sp. nov. and P. chevalieri sp. nov., Cordesia provannoides gen. et sp. nov. (Provannidae); Phymorhynchus coseli sp. nov. and P. cingulata sp. nov. (Conidae); Heterobranchia: Hyalogyrina rissoella sp. nov. (Hyalogyrinidae). All species except T. granulatus (from a settlement trap) belong to groups known from cold seeps and the entire seep fauna here is new to science. Biogeographical affinity of this gastropod fauna is to the West Atlantic seeps, not to the Mediterranean seeps or Mid-Atlantic vents. Fragments of the autecology of the species are presented. The evolution of the seep gastropod fauna is briefly discussed and a continuous immigration of taxa is supported. The oldest verified occurrences of modern taxa in the seeps date back to Cenomanian (Cretaceous) time, while some taxa seem not to appear until very late Tertiary.

  2. Quantification of gas bubble emissions from submarine hydrocarbon seeps at the Makran continental margin (offshore Pakistan)

    NASA Astrophysics Data System (ADS)

    RöMer, Miriam; Sahling, Heiko; Pape, Thomas; Bohrmann, Gerhard; Spieß, Volkhard

    2012-10-01

    Evidence for twelve sites with gas bubble emissions causing hydroacoustic anomalies in 18 kHz echosounder records (`flares') was obtained at the convergent Makran continental margin. The hydroacoustic anomalies originating from hydrocarbon seeps at water depths between 575 and 2870 m disappeared after rising up to 2000 m in the water column. Dives with the remotely operated vehicle `Quest 4000 m' revealed that several individual bubble vents contributed to one hydroacoustic anomaly. Analyzed gas samples suggest that bubbles were mainly composed of methane of microbial origin. Bubble size distributions and rise velocities were determined and the volume flux was estimated by counting the emitted bubbles and using their average volume. We found that a low volume flux (Flare 1 at 575 mbsl: 90 ml/min) caused a weak hydroacoustic signal in echograms whereas high volume fluxes (Flare 2 at 1027 mbsl: 1590 ml/min; Flare 5 C at 2870 mbsl: 760 ml/min) caused strong anomalies. The total methane bubble flux in the study area was estimated by multiplying the average methane flux causing a strong hydroacoustic anomaly in the echosounder record with the total number of equivalent anomalies. An order-of-magnitude estimate further considers the temporal variability of some of the flares, assuming a constant flux over time, and allows a large range of uncertainty inherent to the method. Our results on the fate of bubbles and the order-of-magnitude estimate suggest that all of the ˜40 ± 32 × 106 mol methane emitted per year within the gas hydrate stability zone remain in the deep ocean.

  3. A comparison of hydrocarbon gases from springs and seeps of varied geologic provinces of the northwestern US

    SciTech Connect

    Lorenson, T.D.; Kvenvolden, K.A. )

    1993-04-01

    The northwestern US hosts a remarkable quantity and variety of thermal springs and seeps. Although many studies have dealt with the liquids and non-hydrocarbon gases emanating from these sources, few have focused on hydrocarbon gases. methane in particular is now recognized as an important reactive trace gas in the earth's atmosphere. To understand better the magnitude and occurrence of natural sources of hydrocarbons to the atmosphere, the authors have begun a survey of these gases throughout the northwestern US. This area encompasses a number of different tectonic regimes: the Yellowstone Hot Spot, the northern Basin and Range province, the Cascade volcanic arc, and the Cascadia subduction complex. Methane is present in each area at concentration levels ranging from about 2 ppmv (parts per million by volume) to 99.9% (by volume). Hydrothermal activity in the Yellowstone area produces spring gases containing less than 4% methane, with CO[sub 2] as the balance gas. The Teton area has a wide variety of gas compositions with either methane, carbon dioxide, or nitrogen as the primary gas component. In the northern Great Basin, thermal springs and seeps typically occur along fault zones at the base of mountain ranges. Methane concentrations range from 0.2 to 47%, with HMW HC concentrations from 0 to 3,100 ppmv. Areas covered by the Cenozoic Columbia River basalts and the basalts of the Snake River Plain continue to have high heat flow and produce thermal springs and seeps, usually along fault zones. Gases from the southern Cascade volcanic arc (Mt. Shasta and Mt. Lassen) are composed typically of carbon dioxide, with minor amounts of methane (less than 0.2%); however some fumaroles at Mt. Lassen have minor quantities of HMW HC. Along the Pacific coast, melanges of the Cascadia subduction complex host many seeps and springs. In some seeps the gas consists almost exclusively of methane (94.3 to 99.9%) with amounts of HMW HC ranging from about 5 ppmv to 3.5%.

  4. Microbial sulfate reduction rates and sulfur and oxygen isotope fractionations at oil and gas seeps in deepwater Gulf of Mexico

    SciTech Connect

    Aharon, P.; Fu, B.

    2000-01-01

    sulfate reduction and anaerobic methane oxidation are the dominant microbial processes occurring in hydrate-bearing sediments at bathyal depths in the Gulf of Mexico where crude oil and methane are advecting through fault conduits to the seafloor. The oil and gas seeps are typically overlain by chemosynthetic communities consisting of thiotrophic bacterial mats (Beggiatoa spp.) and methanotrophic mussels (Bathymodiolus spp.), respectively. Cores were recovered with a manned submersible from fine-grained sediments containing dispersed gas hydrates at the threshold of stability. Estimated sulfate reduction rates are variable but generally are substantially higher in crude oil seeps (up to 50 times) and methane seeps (up to 600 times) relative to a non-seep reference sediment. Sulfur and oxygen isotope fractionation factors are highest in the reference sediment but substantially lower in the seep sediments and are controlled primarily by kinetic factors related to sulfate reduction rates. Kinetic effects also control the {delta}{sup 34}S/{delta}{sup 18}O ratios such that slow microbial rates yield low ratios whereas faster rates yield progressively higher ratios. The seep data contradict previous claims that {delta}{sup 34}S/{delta}{sup 18}O ratios are diagnostic of either microbial sulfate reduction at a fixed {delta}{sup 34}S/{delta}{sup 18}O ratio of 4/1 or lower ratios caused by SO{sub 4}-H{sub 2}O equilibration at ambient temperatures. The new results offer a better understanding of methane removal via anaerobic oxidation in the sulfate reduction zone of hydrate-bearing sediments and have significant implications regarding the origin and geochemical history of sedimentary sulfate reconstructed on the basis of {delta}{sup 34}S and {delta}{sup 18}O compositions.

  5. Marine microbes rapidly adapt to consume ethane, propane, and butane within the dissolved hydrocarbon plume of a natural seep

    NASA Astrophysics Data System (ADS)

    Mendes, Stephanie D.; Redmond, Molly C.; Voigritter, Karl; Perez, Christian; Scarlett, Rachel; Valentine, David L.

    2015-03-01

    Simple hydrocarbon gases containing two to four carbons (ethane, propane, and butane) are among the most abundant compounds present in petroleum reservoirs, and are introduced into the ocean through natural seepage and industrial discharge. Yet little is known about the bacterial consumption of these compounds in ocean waters. To assess the timing by which microbes metabolize these gases, we conducted a three-phase study that tested and applied a radiotracer-based method to quantify the oxidation rates of ethane, propane, and butane in fresh seawater samples. Phase 1 involved the synthesis of tritiated ethane, propane, and butane using Grignard reagents and tritiated water. Phase 2 was a systematic assessment of experimental conditions, wherein the indigenous microbial community was found to rapidly oxidize ethane, propane, and butane. Phase 3 was the application of this tritium method near the Coal Oil Point seeps, offshore California. Spatial and temporal patterns of ethane, propane, and butane oxidation down current from the hydrocarbon seeps demonstrated that >99% of these gases are metabolized within 1.3 days following initial exposure. The oxidation of ethane outpaced oxidation of propane and butane with patterns indicating the microbial community responded to these gases by rapid adaptation or growth. Methane oxidation responded the slowest in plume waters. Estimates based on the observed metabolic rates and carbon mass balance suggest that ethane, propane, and butane-consuming microorganisms may transiently account for a majority of the total microbial community in these impacted waters.

  6. Combined carbonate carbon isotopic and cellular ultrastructural studies of individual benthic foraminifera: 2. Toward an understanding of apparent disequilibrium in hydrocarbon seeps

    NASA Astrophysics Data System (ADS)

    Bernhard, Joan M.; Martin, Jonathan B.; Rathburn, Anthony E.

    2010-10-01

    Numerous previous studies show disequilibrium between stable carbon isotope ratios of foraminiferal calcite and pore water dissolved inorganic carbon in hydrocarbon seeps, calling into question the utility of this widely used paleoceanographic tracer as a proxy. We use a recently developed method to compare stable carbon isotope ratios of foraminiferal carbonate with cell ultrastructural observations from individual benthic foraminifera from seep (under chemosynthetic bivalves) and nonseep habitats in Monterey Bay, California, to better understand control(s) of benthic foraminiferal carbon isotope ratios. Two attributes previously proposed to cause the isotopic offsets are diet and symbionts. Ultrastructural analysis shows that positive staining with Rose Bengal indicates presence of foraminiferal cytoplasm, bacterial biomass, or a combination of both and, thus, is not an unequivocal indicator of viability. We also show for the first time that some living seep foraminifera have endobionts. Results from our unique, yet limited, data set are consistent with suggestions that, in our sites, several foraminiferal species collected from seep clam beds may not survive there, diet and symbiont presence do not appear to be major contributors to disequilibrium, little calcification of seep-tolerant foraminiferal species occurs while seep conditions prevail, and microscale variability in habitats could influence δ13C of benthic foraminiferal carbonate. Results further suggest that our knowledge of benthic foraminiferal ecology and biomineralization, especially in extreme habitats such as seeps, must be bolstered before we fully understand the fidelity of paleoenvironmental records derived from benthic foraminiferal test δ13C data.

  7. Methane oxidation in permeable sediments at hydrocarbon seeps in the Santa Barbara Channel, California

    NASA Astrophysics Data System (ADS)

    Treude, T.; Ziebis, W.

    2010-03-01

    A shallow-water area in the Santa Barbara Channel (California), known collectively as the Coal Oil Point seep field, is one the largest natural submarine oil and gas emission areas in the world. Both gas and oil are seeping constantly through a predominantly sandy seabed into the ocean. This study focused on the methanotrophic activity within the surface sediments (0-15 cm) of the permeable seabed in the so-called Brian Seep area at a water depth ~10 m. Detailed investigations of biogeochemical parameters in the sediment surrounding active gas vents indicated that methane seepage through the permeable seabed induces a convective transport of fluids within the surface sediment layer, which results in a deeper penetration of oxidants (oxygen, sulfate) into the sediment, as well as in a faster removal of potentially inhibiting reduced end products (e.g. hydrogen sulfide). Methanotrophic activity was often found close to the sediment-water interface, indicating the involvement of aerobic bacteria. However, biogeochemical data suggests that the majority of methane is consumed by anaerobic oxidation of methane (AOM) coupled to sulfate reduction below the surface layer (>15 cm), where sulfate is still available in high concentrations. This subsurface maximum of AOM activity in permeable sands is in contrast to known deep-sea seep habitats, where upward fluid advection through more fine-grained sediments leads to an accumulation of AOM activity within the top 10 cm of the sediments, because sulfate is rapidly depleted.

  8. Association of oil seeps and chemosynthetic communities with oil discoveries, upper continental slope, Gulf of Mexico

    SciTech Connect

    Sassen, R.; Brooks, J.M.; MacDonald, I.R.; Kennicutt, M.C. II; Guinasso, N.L. Jr. )

    1993-09-01

    A belt of sea-floor oil seeps and chemosynthetic communities has been mapped across the upper continental slope, offshore Louisiana, at depths ranging from 2000 to 1000 m. Visibly oil-stained sediments and thelmogenic gas hydrates have been recovered using piston cores and research submarines. Biomarker fingerprinting of seep oils suggests an origin from deeply buried Cretaceous or Jurassic source rocks characterized by marine kerogen. The abundance of seeps provides a unique opportunity to define their relationship to oil discoveries including Auger, Cooper, Jolliet, Marquette, Vancouver, Popeye, and Mars. Seeps are preferentially distributed over shallow salt ridges that rim intrasalt basin cooking pots, over salt diapirs, and along shallow fault traces near discoveries. Diagnostic seep-related features on the sea floor include gas hydrate mounds and outcrops, pockmarks and craters, mud volcanoes, and carbonate buildups. Many of the 50 chemosynthetic communities including tube worms, mussels, or clams thus far documented in the gulf occur near discoveries. Recent imagery from orbital platforms, including the space shuttle, shows that natural oil slicks are common on the sea surface in this area. Additional mapping of seep distributions should contribute to better defining of the limits of the deep Gulf play fairway.

  9. Using Stable Isotope Compositions of Animal Tissues to Infer Trophic Interactions in Gulf of Mexico Lower Slope Seep Communities

    PubMed Central

    Becker, Erin L.; Cordes, Erik E.; Macko, Stephen A.; Lee, Raymond W.; Fisher, Charles R.

    2013-01-01

    We analyzed the tissue carbon, nitrogen, and sulfur stable isotope contents of macrofaunal communities associated with vestimentiferan tubeworms and bathymodiolin mussels from the Gulf of Mexico lower continental slope (970-2800 m). Shrimp in the genus Alvinocaris associated with vestimentiferans from shallow (530 m) and deep (1400-2800 m) sites were used to test the hypothesis that seep animals derive a greater proportion of their nutrition from seeps (i.e. a lower proportion from the surface) at greater depths. To account for spatial variability in the inorganic source pool, we used the differences between the mean tissue δ13C and δ15N of the shrimp in each collection and the mean δ 13C and δ15N values of the vestimentiferans from the same collection, since vestimentiferans are functionally autotrophic and serve as a baseline for environmental isotopic variation. There was a significant negative relationship between this difference and depth for both δ13C and δ15N (p=0.02 and 0.007, respectively), which supports the hypothesis of higher dependence on seep nutrition with depth. The small polychaete worm Protomystides sp. was hypothesized to be a blood parasite of the vestimentiferan Escarpialaminata. There was a highly significant linear relationship between the δ13C values of Protomystides sp. and the E. laminata individuals to which they were attached across all collections (p < 0.001) and within a single collection (p = 0.01), although this relationship was not significant for δ15N and δ34S. We made several other qualitative inferences with respect to the feeding biology of the taxa occurring in these lower slope seeps, some of which have not been described prior to this study. PMID:24324572

  10. Coastal pollution hazards in southern California observed by SAR imagery: stormwater plumes, wastewater plumes, and natural hydrocarbon seeps

    NASA Technical Reports Server (NTRS)

    Digiacomo, Paul M.; Washburn, Libe; Holt, Benjamin; Jones, Burton H.

    2004-01-01

    Stormwater runoff plumes, municipal wastewater plumes, and natural hydrocarbon seeps are important pollution hazards for the heavily populated Southern California Bight (SCB). Due to their small size, dynamic and episodic nature, these hazards are difficult to sample adequately using traditional in situ oceanographic methods. Complex coastal circulation and persistent cloud cover can further complicate detection and monitoring of these hazards. We use imagery from space-borne synthetic aperture radar (SAR), complemented by field measurements, to examine these hazards in the SCB. The hazards are detectable in SAR imagery because they deposit surfactants on the sea surface, smoothing capillary and small gravity waves to produce areas of reduced backscatter compared with the surrounding ocean. We suggest that high-resolution SAR, which obtains useful data regardless of darkness or cloud cover, could be an important observational tool for assessment and monitoring of coastal marine pollution hazards in the SCB and other urbanized coastal regions.

  11. Coastal pollution hazards in southern California observed by SAR imagery: stormwater plumes, wastewater plumes, and natural hydrocarbon seeps.

    PubMed

    Digiacomo, Paul M; Washburn, Libe; Holt, Benjamin; Jones, Burton H

    2004-12-01

    Stormwater runoff plumes, municipal wastewater plumes, and natural hydrocarbon seeps are important pollution hazards for the heavily populated Southern California Bight (SCB). Due to their small size, dynamic and episodic nature, these hazards are difficult to sample adequately using traditional in situ oceanographic methods. Complex coastal circulation and persistent cloud cover can further complicate detection and monitoring of these hazards. We use imagery from space-borne synthetic aperture radar (SAR), complemented by field measurements, to examine these hazards in the SCB. The hazards are detectable in SAR imagery because they deposit surfactants on the sea surface, smoothing capillary and small gravity waves to produce areas of reduced backscatter compared with the surrounding ocean. We suggest that high-resolution SAR, which obtains useful data regardless of darkness or cloud cover, could be an important observational tool for assessment and monitoring of coastal marine pollution hazards in the SCB and other urbanized coastal regions. PMID:15556188

  12. Novel Alkane Hydroxylase Gene (alkB) Diversity in Sediments Associated with Hydrocarbon Seeps in the Timor Sea, Australia▿

    PubMed Central

    Wasmund, Kenneth; Burns, Kathryn A.; Kurtböke, D. Ipek; Bourne, David G.

    2009-01-01

    Hydrocarbon seeps provide inputs of petroleum hydrocarbons to widespread areas of the Timor Sea. Alkanes constitute the largest proportion of chemical components found in crude oils, and therefore genes involved in the biodegradation of these compounds may act as bioindicators for this ecosystem's response to seepage. To assess alkane biodegradation potential, the diversity and distribution of alkane hydroxylase (alkB) genes in sediments of the Timor Sea were studied. Deduced AlkB protein sequences derived from clone libraries identified sequences only distantly related to previously identified AlkB sequences, suggesting that the Timor Sea maybe a rich reservoir for novel alkane hydroxylase enzymes. Most sequences clustered with AlkB sequences previously identified from marine Gammaproteobacteria though protein sequence identities averaged only 73% (with a range of 60% to 94% sequence identities). AlkB sequence diversity was lower in deep water (>400 m) samples off the continental slope than in shallow water (<100 m) samples on the continental shelf but not significantly different in response to levels of alkanes. Real-time PCR assays targeting Timor Sea alkB genes were designed and used to quantify alkB gene targets. No correlation was found between gene copy numbers and levels of hydrocarbons measured in sediments using sensitive gas chromatography-mass spectrometry techniques, probably due to the very low levels of hydrocarbons found in most sediment samples. Interestingly, however, copy numbers of alkB genes increased substantially in sediments exposed directly to active seepage even though only low or undetectable concentrations of hydrocarbons were measured in these sediments in complementary geochemical analyses due to efficient biodegradation. PMID:19820158

  13. Tracing the composition and origin of fluids at an ancient hydrocarbon seep (Hollard Mound, Middle Devonian, Morocco): A Nd, REE and stable isotope study

    NASA Astrophysics Data System (ADS)

    Jakubowicz, M.; Dopieralska, J.; Belka, Z.

    2015-05-01

    For the first time, Nd isotope signatures combined with rare earth element (REE) concentrations were used in investigations of ancient seep carbonates. The study was performed on the fossil hydrocarbon seep deposit of the Middle Devonian Hollard Mound (eastern Anti-Atlas, Morocco), where Nd isotopes, REE concentrations, and carbon and oxygen isotope ratios were measured to investigate the origin, former migration pathways and composition of fluids. Relatively high εNd values compared to local Eifelian seawater, as well as consistently appearing positive Eu anomalies in MREE-enriched shale-normalized REE patterns of the seep carbonates provided evidence for interaction between the seeping fluids and the Lower Devonian basaltic volcaniclastics underlying the studied seep deposit. Strongly reducing conditions and increased temperature of methane formation could have constituted an additional factor in the Eu-enrichment of the investigated carbonate phases. The presence of exclusively negative Ce anomalies in these carbonates is in line with observations of other workers that seep limestones may not necessarily display positive Ce anomalies indicative of precipitation under anoxic conditions. The negative Ce anomalies are attributed here to mixing between anoxic pore waters and oxic, Ce-depleted seawater, necessary to enable carbonate precipitation at seeps. The methane-rich fluids ascended most likely from below the volcaniclastic unit and inherited the enriched εNd signatures and positive Eu anomalies due to fluid-rock interactions during their seepage to the seafloor. The carbon isotope data are most consistent with thermogenic origin of methane, although contribution of abiotic and biogenic methane sources cannot be excluded. Our results indicate that neodymium isotope and rare earth element analyses constitute one of the most valuable tools for reconstructing former fluid migration patterns. The study shows also that Nd isotopes and Eu anomalies can serve as

  14. Hydrocarbon flux from natural deepwater Gulf of Mexico vents

    NASA Astrophysics Data System (ADS)

    Smith, Andrew J.; Flemings, Peter B.; Fulton, Patrick M.

    2014-06-01

    High salinities and high temperatures at the seafloor record the upward flow of water and hydrocarbons from depth at natural vents in the deepwater Gulf of Mexico. We present a multiphase heat- and solute-transport model, in which water supplied from depth transports heat and salt, and hydrocarbon transports heat. We show that there is a unique water and hydrocarbon flux that simulates the observed salinity and temperature. We estimate the hydrocarbon flux to be 3.2-15×104 t yr and 1.8-8.0×104 t yr from two vents at lease blocks MC852/853 and GB425. These fluxes are 1-4 orders of magnitude greater than previous estimates from individual deepwater vents. If these results are extrapolated to the entire Gulf of Mexico, then we estimate the regional hydrocarbon flux to be at least 100× greater than previous estimates and 14-120% of the hydrocarbon flux from the Macondo oil spill. Large natural seepage may inoculate marine basins such as the Gulf of Mexico from oil spills like the 2010 Deepwater Horizon blowout by sustaining populations of hydrocarbon-degrading bacteria.

  15. Presence and diversity of anammox bacteria in cold hydrocarbon-rich seeps and hydrothermal vent sediments of the Guaymas Basin.

    PubMed

    Russ, Lina; Kartal, Boran; Op den Camp, Huub J M; Sollai, Martina; Le Bruchec, Julie; Caprais, Jean-Claude; Godfroy, Anne; Sinninghe Damsté, Jaap S; Jetten, Mike S M

    2013-01-01

    Hydrothermally active sediments are highly productive, chemosynthetic areas which are characterized by the rapid turnover of particulate organic matter under extreme conditions in which ammonia is liberated. These systems might be suitable habitats for anaerobic ammonium oxidizing (anammox) bacteria but this has not been investigated in detail. Here we report the diversity and abundance of anammox bacteria in sediments that seep cold hydrocarbon-rich fluids and hydrothermal vent areas of the Guaymas Basin in the Cortés Sea using the unique functional anammox marker gene, hydrazine synthase (hzsA). All clones retrieved were closely associated to the "Candidatus Scalindua" genus. Phylogenetic analysis revealed two distinct clusters of hzsA sequences (Ca. Scalindua hzsA cluster I and II). Comparison of individual sequences from both clusters showed that several of these sequences had a similarity as low as 76% on nucleotide level. Based on the analysis of this phylomarker, a very high interspecies diversity within the marine anammox group is apparent. Absolute numbers of anammox bacteria in the sediments samples were determined by amplification of a 257 bp fragment of the hszA gene in a qPCR assay. The results indicate that numbers of anammox bacteria are generally higher in cold hydrocarbon-rich sediments compared to the vent areas and the reference zone. Ladderanes, lipids unique to anammox bacteria were also detected in several of the sediment samples corroborating the hzsA analysis. Due to the high concentrations of reduced sulfur compounds and its potential impact on the cycling of nitrogen we aimed to get an indication about the key players in the oxidation of sulfide in the Guaymas Basin sediments using the alpha subunit of the adenosine-5'-phosphosulfate (APS) reductase (aprA). Amplification of the aprA gene revealed a high number of gammaproteobacterial aprA genes covering the two sulfur-oxidizing bacteria aprA lineages as well as sulfate-reducers. PMID

  16. Hydrocarbon flux from natural deepwater Gulf of Mexico vents

    NASA Astrophysics Data System (ADS)

    Flemings, P. B.; Smith, A. J.

    2012-12-01

    Natural vents that expel water and hydrocarbons are present on continental margins around the world. The expelled fluids support biological vent communities, escape to the ocean and atmosphere, and may contribute significantly to oceanic and atmospheric carbon budgets. We describe two vents in the northern Gulf of Mexico (GoM) at lease blocks MC852/853 and GB425 that have significant flow, high salinities, and elevated temperatures. We use a steady state multi-phase flow model and show that there is a unique water and hydrocarbon flux that simulates the observed salinity and temperature. We estimate the hydrocarbon flux at each vent to be 2.0-9.9x104 t yr-1 and 1.7-7.1x104 t yr-1, respectively. We extrapolate these results and estimate the hydrocarbon flux from the entire Gulf of Mexico to be 9.7-55x106 t yr-1. This flux is at least 50x greater than previous estimates11 and is 6-40% of the hydrocarbon flux from the Macondo oil spill. Large natural seepage may inoculate marine basins such as the Gulf of Mexico from oil spills like the 2010 Deepwater Horizon blowout by sustaining populations of hydrocarbon-degrading bacteria.

  17. Bacterial Endophytes Isolated from Plants in Natural Oil Seep Soils with Chronic Hydrocarbon Contamination

    PubMed Central

    Lumactud, Rhea; Shen, Shu Yi; Lau, Mimas; Fulthorpe, Roberta

    2016-01-01

    The bacterial endophytic communities of four plants growing abundantly in soils highly contaminated by hydrocarbons were analyzed through culturable and culture-independent means. Given their tolerance to the high levels of petroleum contamination at our study site, we sought evidence that Achillea millefolium, Solidago canadensis, Trifolium aureum, and Dactylis glomerata support high levels of hydrocarbon degrading endophytes. A total of 190 isolates were isolated from four plant species. The isolates were identified by partial 16S rDNA sequence analysis, with class Actinobacteria as the dominant group in all species except S. canadensis, which was dominated by Gammaproteobacteria. Microbacterium foliorum and Plantibacter flavus were present in all the plants, with M. foliorum showing predominance in D. glomerata and both endophytic bacterial species dominated T. aureum. More than 50% of the isolates demonstrated degradative capabilities for octanol, toluene, naphthalene, kerosene, or motor oil based on sole carbon source growth screens involving the reduction of tetrazolium dye. P. flavus isolates from all the sampled plants showed growth on all the petroleum hydrocarbons (PHCs) substrates tested. Mineralization of toluene and naphthalene was confirmed using gas-chromatography. 16S based terminal restriction fragment length polymorphism analysis revealed significant differences between the endophytic bacterial communities showing them to be plant host specific at this site. To our knowledge, this is the first account of the degradation potential of bacterial endophytes in these commonly occurring pioneer plants that were not previously known as phytoremediating plants. PMID:27252685

  18. Geochemical characteristics of the barite deposits at cold seeps from the northern Gulf of Mexico continental slope

    NASA Astrophysics Data System (ADS)

    Feng, Dong; Roberts, Harry H.

    2011-09-01

    Although less common than the occurrence of authigenic carbonate, barite has been observed frequently at cold seeps on continental margins worldwide. It is understood that barite forms by the interaction of barium-rich and sulfate-free seeping fluids with dissolved sulfate of pore water near the seafloor, but questions remain about the geochemical processes and mode(s) of the barite formation. Here, we report geochemical characteristics of barite deposits at 11 cold seep locations from the northern Gulf of Mexico continental slope. Samples from these sites of fluid and gas expulsion provide environmental information on barite formation. Seafloor observations and samples acquired indicate that barites occur as chimneys, cones, crusts, irregular mound-like buildups up to 2-meters high, and as a material disseminated in host sediment. Most barite samples are white-to-gray and usually have a porous fabric and layered internal structure. Mineralogically, samples of barite may contain a significant amounts of carbonate minerals, such as calcite and dolomite, but aragonite is absent in all samples analyzed in this study. Negative δ 13C values (as low as - 46.4‰ V-PDB) of the associated carbonates strongly suggests that methane is the primary carbon source. The δ 34S and δ 18O values of the barites have large variations, ranging from 18‰ to 80.4‰ V-CDT, and 7.5‰ to 26.7‰ V-SMOW, respectively. On δ 34S versus δ 18O plots, many barite deposits show a linear trend that projects down toward the isotopic composition of seawater sulfate. The trend suggests that barite formed from seawater sulfate that has been isotopically modified to varying degrees by biological sulfate reduction. The δ 34S/δ 18O ratios vary between 2.4 and 4.1. The variations are interpreted to reflect local controls on the flux of barium-rich seep fluids, changes in the rate of bacterial sulfate reduction, and/or the openness of pore fluid system. The 87Sr/ 86Sr values of the barites

  19. Pore Water Composition at Gas Seeps in the Northern Gulf of Mexico: Understanding Flow Regime and Chemical Processes

    NASA Astrophysics Data System (ADS)

    Hubbard, L. A.; Dugan, B.; Dickens, G. R.

    2006-12-01

    Cold seeps on continental slopes discharge large quantities of gas and fluid to the ocean. The expulsion rate and composition of seep fluids can vary significantly in space and time, which can affect local biological and chemical processes. The factors influencing variability in flux and composition, however, are not fully documented. For this study, we have collected and analyzed pore fluids at four sites in the northern Gulf of Mexico: Atwater Valley (AV), Mississippi Canyon (MC), Garden Banks (GB) and Keathley Canyon (KC). The magnitude of fluid discharge is likely highest at the GB and MC sites where active mounds are comparatively larger in size, high heat flux exists across the mounds, and recent mudflow deposits flank the mounds. The AV site samples characterize a smaller mound that may still be growing. Fluxes at the KC site are diffusive and methane-charged, but no mound exists. A comparison of the major ions and trace metals in the pore fluids shows large differences in composition. Pore water barium (Ba2+) values demonstrate the most variation between sites. The maximum Ba2+ values at the GB and MC sites reach 7,800 μM and 12,000 μM. This is two orders of magnitude greater than maximum values at the AV (176 μM) and KC (31 μM) sites. Other components, such as salinity, calcium (Ca2+) and strontium (Sr2+) also record differences in composition between the sites. Pore water salinity values measured at the MC and GB sites reach a maximum of 130 ‰, which is at least 2 times greater than values measured at the AV and KC sites. Differences in pore water Ca2+ and Sr2+ are similar to salinity; in general, maximum values are two times greater at GB and MC than at Atwater Valley and Keathley Canyon. The observed differences in pore water composition are the result of the seep fluid source and the chemical processes (e.g., dissolution and precipitation) that occur during migration. Fluid sources and reaction pathways will be evaluated by integrating pore water

  20. Constraints on Methane and Methane Hydrate Distribution at a Gulf of Mexico Seep Using Waveform Inversion of Seismic Data

    NASA Astrophysics Data System (ADS)

    Wood, W.; Knapp, C. C.; Knapp, J. H.

    2010-12-01

    The seafloor mound at the Gulf of Mexico lease block MC (Mississippi Canyon) 118 is a known active seep lying directly above a salt dome. The site lies at 850-900 m water depth - within the methane hydrate stability zone, but there is no obvious BSR or other indicator of large quantities of gas or gas hydrate. Air-gun seismic data acquired with a 4180 cu in source and 7200 m, 288-channel hydrophone array, exhibit several bright, but laterally-limited reflections in the ~500 m sediment column above the salt. The bright spots are largely conformable with the strata, and there is no apparent pull-up or push-down associated with the bright spots, suggesting they are thin. There are also no significant frequency changes below the bright spots. We interpret the bright spots to be caused by gas, gas hydrate, or carbonate, or combinations of the three. The long offsets used to acquire these data allow for the analysis of refracted arrivals that not only provide accurate P-wave velocities, but also provide a background velocity profile for full waveform inversion. Preliminary results from the waveform inversion confirm at least some of the bright spots are free gas, constraining the position of the gas hydrate stability zone, but very thin (sub-wavelength) layers of carbonate and hydrate may also be present. Knowing the exact composition of the material responsible for the bright spots will better constrain the linkage between the salt tectonics (with implied fault activity) and seep activity, as well as the longevity of the hydrate system at MC 118.

  1. Split-beam echo sounder observations of natural methane seep variability in the northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Jerram, Kevin; Weber, Thomas C.; Beaudoin, Jonathan

    2015-03-01

    A method for positioning and characterizing plumes of bubbles from marine gas seeps using an 18 kHz scientific split-beam echo sounder (SBES) was developed and applied to acoustic observations of plumes of presumed methane gas bubbles originating at approximately 1400 m depth in the northern Gulf of Mexico. A total of 161 plume observations from 27 repeat surveys were grouped by proximity into 35 clusters of gas vent positions on the seafloor. Profiles of acoustic target strength per vertical meter of plume height were calculated with compensation for both the SBES beam pattern and the geometry of plume ensonification. These profiles were used as indicators of the relative fluxes and fates of gas bubbles acoustically observable at 18 kHz and showed significant variability between repeat observations at time intervals of 1 h-7.5 months. Active gas venting was observed during approximately one third of the survey passes at each cluster. While gas flux is not estimated directly in this study owing to lack of bubble size distribution data, repeat surveys at active seep sites showed variations in acoustic response that suggest relative changes in gas flux of up to 1 order of magnitude over time scales of hours. The minimum depths of acoustic plume observations at 18 kHz averaged 875 m and frequently coincided with increased amplitudes of acoustic returns in layers of biological scatterers, suggesting acoustic masking of the gas bubble plumes in these layers. Minimum plume depth estimates were limited by the SBES field of view in only five instances.

  2. Authigenic carbonate formation at hydrocarbon seeps in continental margin sediments: A comparative study

    USGS Publications Warehouse

    Naehr, T.H.; Eichhubl, P.; Orphan, V.J.; Hovland, M.; Paull, C.K.; Ussler, W., III; Lorenson, T.D.; Greene, H. Gary

    2007-01-01

    Authigenic carbonates from five continental margin locations, the Eel River Basin, Monterey Bay, Santa Barbara Basin, the Sea of Okhotsk, and the North Sea, exhibit a wide range of mineralogical and stable isotopic compositions. These precipitates include aragonite, low- and high-Mg calcite, and dolomite. The carbon isotopic composition of carbonates varies widely, ranging from -60??? to +26???, indicating complex carbon sources that include 13C-depleted microbial and thermogenic methane and residual, 13C-enriched, bicarbonate. A similarly large variability of ??18O values (-5.5??? to +8.9???) demonstrates the geochemical complexity of these sites, with some samples pointing toward an 18O-enriched oxygen source possibly related to advection of 18O-enriched formation water or to the decomposition of gas hydrate. Samples depleted in 18O are consistent with formation deeper in the sediment or mixing of pore fluids with meteoric water during carbonate precipitation. A wide range of isotopic and mineralogical variation in authigenic carbonate composition within individual study areas but common trends across multiple geographic areas suggest that these parameters alone are not indicative for certain tectonic or geochemical settings. Rather, the observed variations probably reflect local controls on the flux of carbon and other reduced ions, such as faults, fluid conduits, the presence or absence of gas hydrate in the sediment, and the temporal evolution of the local carbon reservoir. Areas with seafloor carbonates that indicate formation at greater depth below the sediment-water interface must have undergone uplift and erosion in the past or are still being uplifted. Consequently, the occurrence of carbonate slabs on the seafloor in areas of active hydrocarbon seepage is commonly an indicator of exhumation following carbonate precipitation in the shallow subsurface. Therefore, careful petrographic and geochemical analyses are critical components necessary for the

  3. Influence of foundation species, depth, and location on diversity and community composition at Gulf of Mexico lower-slope cold seeps

    NASA Astrophysics Data System (ADS)

    Cordes, Erik E.; Becker, Erin L.; Hourdez, Stephane; Fisher, Charles R.

    2010-11-01

    Efforts to understand and preserve the seep communities of the deep Gulf of Mexico (GOM) begin with a comprehensive survey of the biodiversity of these communities. Previous studies have provided a conceptual model of the physiology, population, and community ecology of upper continental slope seeps. However, seeps at water depths below 1000 m in the Gulf of Mexico remain relatively unknown. In this study, data from 47 samples of tubeworm- and mussel-associated communities at depths of 1005-2750 m are examined. Other than tubeworms and mussels, 66 taxa of macro- and megafauna were collected, 43 of which appear to be restricted to water depths of over 1000 m, and 39 that have not been reported previously from the Gulf of Mexico. Diversity in mussel beds was highest at mid-slope depths, but tubeworm-associated communities did not show clear bathymetric trends in diversity. Diversity was higher in tubeworm aggregations at the alpha level (per sample), but higher in mussel beds at the beta level (species turnover among collections). Although both community types were often numerically dominated by the endemic shrimp Alvinocaris muricola, broad differences in the communities hosted by tubeworm aggregations and mussel beds were apparent. The most important factors explaining community similarity within community type were the depth, relative abundance of different mussel species in a bed, and the average size of tubeworms in an aggregation. The high proportion of deep-seep species that were found for the first time in the Gulf of Mexico emphasizes the importance of conservation efforts for these patchy communities.

  4. Presence and diversity of anammox bacteria in cold hydrocarbon-rich seeps and hydrothermal vent sediments of the Guaymas Basin

    PubMed Central

    Russ, Lina; Kartal, Boran; op den Camp, Huub J. M.; Sollai, Martina; Le Bruchec, Julie; Caprais, Jean-Claude; Godfroy, Anne; Sinninghe Damsté, Jaap S.; Jetten, Mike S. M.

    2013-01-01

    Hydrothermally active sediments are highly productive, chemosynthetic areas which are characterized by the rapid turnover of particulate organic matter under extreme conditions in which ammonia is liberated. These systems might be suitable habitats for anaerobic ammonium oxidizing (anammox) bacteria but this has not been investigated in detail. Here we report the diversity and abundance of anammox bacteria in sediments that seep cold hydrocarbon-rich fluids and hydrothermal vent areas of the Guaymas Basin in the Cortés Sea using the unique functional anammox marker gene, hydrazine synthase (hzsA). All clones retrieved were closely associated to the “Candidatus Scalindua” genus. Phylogenetic analysis revealed two distinct clusters of hzsA sequences (Ca. Scalindua hzsA cluster I and II). Comparison of individual sequences from both clusters showed that several of these sequences had a similarity as low as 76% on nucleotide level. Based on the analysis of this phylomarker, a very high interspecies diversity within the marine anammox group is apparent. Absolute numbers of anammox bacteria in the sediments samples were determined by amplification of a 257 bp fragment of the hszA gene in a qPCR assay. The results indicate that numbers of anammox bacteria are generally higher in cold hydrocarbon-rich sediments compared to the vent areas and the reference zone. Ladderanes, lipids unique to anammox bacteria were also detected in several of the sediment samples corroborating the hzsA analysis. Due to the high concentrations of reduced sulfur compounds and its potential impact on the cycling of nitrogen we aimed to get an indication about the key players in the oxidation of sulfide in the Guaymas Basin sediments using the alpha subunit of the adenosine-5′-phosphosulfate (APS) reductase (aprA). Amplification of the aprA gene revealed a high number of gammaproteobacterial aprA genes covering the two sulfur-oxidizing bacteria aprA lineages as well as sulfate

  5. Marine oil seeps

    SciTech Connect

    Meyer, R.F. )

    1991-03-01

    Petroleum hydrocarbons of both biogenic and thermogenic origin are common constituents of the marine water column and sediment of the continental shelves. Approximately 0.25 million metric tons of oil per year, constituting about 8% of the oil input into the sea, is derived from natural seeps, the rest being anthropogenic. Seepage has occurred world-wide for millions of years and must have been many times greater in the past, when enormous oil deposits, such as the Orinoco Oil Belt, were first exposed to erosion. Although the amount varies from site to site with time, seepage is pervasive in polar and temperate seas. Marine-seep oil is intensely weathered and thus can be distinguished chemically from recent biogenic or undegraded crude oil. The degraded oil from seeps appears to have little deleterious effect on many marine organisms, which ingest and discharge the oil mostly unmetabolized. Chemical analyses suggest that a very large oil-rich layer in the Sargasso Sea originated from a large and as yet undetected seep. Oil seeps have long been used as guides for oil exploration onshore but have been underutilized for this purpose offshore because of oil-plume drift from the site of the seep and because natural oil slicks may be masked by spilled oil. At least one marine seep, in the Santa Barbara Channel, California, is producing oil and natural gas into two hollow steel pyramids from which the oil is collected by work boats and the natural gas is transported to shore by pipeline. This facility effectively reduces atmospheric pollution, controls marine oil pollution from the largest seep in the area, provides emission credits, and yields a modest economic benefit, but the seep is not known to have been used directly in oil exploration.

  6. Distribution of subsurface hydrocarbon seepage in near surface marine sediments

    SciTech Connect

    Abrams, M.A. )

    1993-02-01

    Hydrocarbon seeps in surficial marine sediments are of two types: ACTIVE: Where gas bubbles, pockmarks, or bright spots are visible on seismic records and/or the presence of chemosynthetic communities in conjunction with large concentrations of migrated-hydrocarbons. Generally in areas where generation and migration of hydrocarbons from the source rock is ongoing today (i.e., maximum burial) and/or where significant migration pathways have developed from tectonic activity. PASSIVE: Where concentrations of migrated hydrocarbons are so low that few or no geophysical anomalies are seen. Typically in areas where generation and expulsion is relict (no longer at maximum burial) and/or regional seals prevent significant vertical migration. The type of seep strongly controls the distribution of migrated hydrocarbons in the near surface sediments and should dictate the sampling equipment and approach required to detect seeps. Active seeps or macroseeps, usually can be detected near the water-sediment interface, within the water column, and at relatively large distances from major leak points. Most conventional sediment and water samplers will capture active seeps, Precise location of sampling is typically not critical to detect active seeps. The Gulf of Mexico, Santa Barbara Channel, and parts of the North Sea have active hydrocarbon seeps.

  7. Origin of hydrocarbons in Gulf of Mexico basin: A reappraisal

    SciTech Connect

    Bissada, K.K.; Katz, B.J.; Barnicle, S.C.; Schunk, D.J.

    1988-01-01

    The origin of hydrocarbons in the Gulf of Mexico basin has been a subject of controversy for many years. One argument invokes source rocks of average organic enrichment, pervasively distributed throughout the Tertiary sequence and closely associated with the reservoir system. Another argument invokes exceptionally rich, discrete source rocks not in contact with the reservoirs, possibly in pre-Tertiary sequences. Continued exploration success in the basin hinges on the resolution of this controversy because of implications on patterns of hydrocarbon migration within the basin and the timing of petroleum generation relative to reservoir and trap development. Geochemical analyses of hundreds of crude oils, natural gases, and nonreservoir rocks from the Mesozoic and Cenozoic trends along the northern Gulf of Mexico basin indicate the general inadequacy of the Tertiary section to source the huge oil accumulations within Cenozoic reservoirs. Furthermore, other than the biogenic gas, isotopic data indicate that the majority of nonassociated gases found in Cenozoic accumulations have been thermogenically derived from much greater depths where maturation is consistent with dry gas generation. Geochemical data from several Mesozoic units in the basin, but outside the Cenozoic trend proper, indicate the existence of excellent Mesozoic source rocks. It is proposed that such units extend below the Cenozoic producing trends and are drained by deep-seated faults and piercement salt structures. Maturation history, structural style, and patterns of migration and remigration control the variable productivity along the various trends.

  8. Testing the link between hydrocarbon seepage, sea level stands, and salt diapirism in deepwater Gulf of Mexico

    SciTech Connect

    Aharon, P.

    1996-09-01

    Hydrocarbon seepage in both liquid (crude oil) and gas (principally methane) forms has been amply documented over the past decade from submersible dives on the northern Gulf of Mexico seafloor overlying salt diapirs. These seepage sites are inhabited by a remarkably diverse chemosynthetic fauna and are associated with massive carbonate buildups formed through bacterially-mediated processes of hydrocarbon oxidation coupled with sulfate reduction. This study addresses questions concerning the timing and longevity of seepage from four representative sites in the Green Canyon area (27{degrees}50{prime}N; 91{degrees}30{prime}W) on the basis of radiometric dating assays of massive carbonates that act as time keepers of hydrocarbon seeps. {sup 230}Th dates from GC-140 and GC-184 blocks place the initiation and termination of massive seepage there at 195 {+-} 25 Ka and 13.3 {+-} 2.7 Ka, respectively, and are in agreement with the chronology of the salt dome emplacement at shallow depth during mid- to late-Pleistocene low sea-level stands. The prolific seepage activity to the southeast in GC-185 (Bush Hill) and the {sup 230}Th dates of 3.2 to 1.4 Ka are attributed to a recent episode of subsidence caused by salt withdrawal which created late normal faults. When multiple dates, subsurface imaging of the salt domes by 3-D seismics, and high resolution subsurface chronostratigraphy are available from the same site, a link is apparent between the incidence of low sea level stands, salt diapirism, and enhanced hydrocarbon seepage.

  9. Gas and gas hydrate distribution around seafloor seeps in Mississippi Canyon, Northern Gulf of Mexico, using multi-resolution seismic imagery

    USGS Publications Warehouse

    Wood, W.T.; Hart, P.E.; Hutchinson, D.R.; Dutta, N.; Snyder, F.; Coffin, R.B.; Gettrust, J.F.

    2008-01-01

    To determine the impact of seeps and focused flow on the occurrence of shallow gas hydrates, several seafloor mounds in the Atwater Valley lease area of the Gulf of Mexico were surveyed with a wide range of seismic frequencies. Seismic data were acquired with a deep-towed, Helmholz resonator source (220-820 Hz); a high-resolution, Generator-Injector air-gun (30-300 Hz); and an industrial air-gun array (10-130 Hz). Each showed a significantly different response in this weakly reflective, highly faulted area. Seismic modeling and observations of reversed-polarity reflections and small scale diffractions are consistent with a model of methane transport dominated regionally by diffusion but punctuated by intense upward advection responsible for the bathymetric mounds, as well as likely advection along pervasive filamentous fractures away from the mounds.

  10. Chronic, Anthropogenic Hydrocarbon Releases in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Daneshgar Asl, S.; Amos, J.; Woods, P.; Garcia-Pineda, O. G.; MacDonald, I. R.

    2012-12-01

    We used satellite remote sensing to quantify hydrocarbon releases cataloged in the Gulf of Mexico. Satellite SAR has frequently been used for detecting small volume releases of oil in the Gulf. Hydrocarbon compounds reduce water surface roughness and therefore can be detected on SAR images as dark areas. We compiled National Response Center (NRC) oil and hazardous materials spill reports in the Gulf of Mexico submitted by the polluters and by passers-by, collected and filtered by SkyTruth from 2001 to 2012 and determined whether the reports coincided with archived SAR images. So, 316 out of a total 4,574 reports could be investigated from 64 SAR images over the report locations. Some of the images covered multiple reports and oil releases described one report could be observed in more than one image. Current information on platforms, pipeline locations, and ages provided by the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEM) can also help us in identifying sources of anthropogenic pollution. The visibility analysis indicated 66 reports of releases were from pipeline, platforms or other anthropogenic sources. Of these, 21 could be seen in SAR images. There were also 133 reports of releases from unknown sources. Of these, 28 were visible in the images. Moreover, 103 anthropogenic reports were attributed to the Taylor offshore platform (platform 23051 in Mississippi Canyon Block 20) which was destroyed during Hurricane Ivan in 2004 and subsequently removed. Of those, 55 were visible in the SAR images and were significantly larger when compared with other reported anthropogenic slicks. The rest of the reports were coded invisible for reasons such as attendance of multiple slicks which makes the decision difficult, report falling outside of the image, image contrast, noisy image, no slick at all, wrong coding, and no slick at the site but another slick in proximity. We then focused on the size of the visible reports which were extracted. The

  11. Megafauna recovered from a cold hydrocarbon seep in the deep Alaskan Beaufort Sea, including a new species of Axinus (Thracidae: Bivalvia: Mollusca)

    NASA Astrophysics Data System (ADS)

    Powell, C. L.; Valentich-Scott, P.; Lorenson, T. D.; Edwards, B. D.

    2011-12-01

    Several specimens of a new species of Axinus and a single well-worn gastropod columella provisionally assigned to the genus Neptunea (Buccinidae: Gastropoda: Mollusca) were recently recovered from at least two cores, the longest of which is 5.72 m long, from a large seafloor mound, informally named the Canning Seafloor Mound (CSM). The CSM is located at 2,530 m water depth on the Alaskan Beaufort Sea slope north of Camden Bay and is a fluid explosion feature containing methane hydrate and methane-saturated sediments overlying a folded and faulted deep basin. Only two modern species of Axinus are currently known. Axinus grandis (Verrill & Smith, 1885) is a northern Atlantic species and the recently described species, A. cascadiensis Oliver and Holmes (2007), is only known from Baby Bare Seamount, Cascadia Basin, northeastern Pacific Ocean. Common fragments, single valves, and a single articulated specimen represent this new Axinus species. These shells were distributed over nearly the entire length of the primary core. All specimens show wear and (or) dissolution. The age of these specimens is unknown and no living representatives were encountered. The genus Axinus has a fossil record back to the early Eocene in England and the Paleocene and Eocene in Egypt. Biogeographically the genus appears to have originated in the Tethys Sea and became established in the Atlantic Ocean during the Eocene, spreading across the Arctic Ocean in the late Tertiary. With the opening of the Bering Strait in the latest Miocene or early Pliocene the genus Axinus migrated southwest into the northeast Pacific. Interestingly, hydrocarbon seep deposits are also present on the adjacent North Slope of Alaska in the Marsh Anticline at Carter Creek, Camden Bay. These rocks, the Nuwok beds, contain abundant Thracidae bivalve of the genus Thracia, but not Axinus, however the rocks also represent cold seep deposits. These rocks have been variously dated from Oligocene to Pliocene and the exact age

  12. Tectono-Stratigraphy of the Seeps on the Guaymas Basin at the Sonora Margin, Gulf of California, Mexico

    NASA Astrophysics Data System (ADS)

    Figueroa Albornoz, L. J.; Mortera-Gutierrez, C. A.; Bandy, W. L.; Escobar-Briones, E. G.; Godfroy, A.; Fouquet, Y.

    2013-05-01

    Recently several hydrothermal and gas seeps systems has been located precisely at the Sonora margin within the Guaymas Basin (GB), Gulf of California. Since late 1970's , several marine studies had reported two main hydrothermal systems in the Guaymas Rift (one at the Northern Rift, and other at the Southern Rift) and a cold seeps system at the Satellite Basin in the Sonora-margin lower edge. During the campaign BIG10, onboard the IFREMER vessel, NO L'Atalante, the EM122 echo-sounder log more than 30,000 water column acoustic images, which allows us to create a data base of the bubble plumes active systems on the northern part of the GB and the Sonora Margin. These plumes are the expression on the water column of an active seeps site during the cruise time. These images document the presence of the cold seep activity around the scarp of the Guaymas Transform Fault (GTF), and within the Satellite Basin. Few active plumes are first located off-axis, on both sides of the Northern Rift. Although it is not observed any plume within NR. Sub-bottom profiles and bathymetric data logged during the campaign GUAYRIV10, onboard the UNAM vessel, BO EL PUMA, are analyzed to determine the shallow tectonic-stratigraphy of GB near the Sonora Margin. We analyze 17 high-resolution seismic profiles (13 with NE-SW strike and 3 with NW-SE strike). From this data set, the continental shelf stratigraphy at the Sonora Margin tilts toward the slope, showing 3 low angle unconformities due to tectonics and slope angle changes. The strata slope changes angle up to 60°. However, the constant trans-tension shear along the GTF causes gravitation instability on the slope, generating a few submarine landslides close to the Northern Rift, and the rotation of blocks, tilting toward the shelf. To the north, the GTF splits in two fault escarpments, forming a narrow pull-apart basin, known as Satellite Basin. The submarine canyon from the Sonora River flows through the Satellite Basin into the GB

  13. HYDROCARBON AND CARBONYL OZONE PRECURSORS IN MEXICO CITY AMBIENT AIR

    EPA Science Inventory

    Urban air pollution is an environmental problem in many cities around the world that has serious immediate and long-term implications to the health of the population and to the physical environment. Mexico City, in particular, faces a severe air pollution problem. The city is...

  14. Chemistry and mineralogy of pyrite-enriched sediments at a passive margin sulfide brine seep: abyssal Gulf of Mexico

    USGS Publications Warehouse

    Commeau, R.F.; Paull, C.K.; Commeau, J.A.; Poppe, L.J.

    1987-01-01

    Pyrite is rapidly accumulating at the contact between the Cretaceous limestones of the Florida Platform and the hemipelagic sediments of the abyssal Gulf of Mexico. Sediments sampled with the submersible "Alvin" in 3266 m of water are associated with a dense community of organisms that depend on chemosynthetic primary production as a food source. Analysis of the chemistry, mineralogy, and textural composition of these sediments indicate that iron sulfide mineralization is occurring at the seafloor within an anoxic micro-habitat sustained by the advection of hydrogen sulfide-charged saline brines from the adjacent platform. The chemosynthetic bacteria that directly overlie the sediments oxidize hydrogen sulfide for energy and provide elemental sulfur that reacts with iron monosulfide to form some of the pyrite. The sediments are mixtures of pyrite (??? 30 wt.%), BaSr sulfates (??? 4 wt.%), clays, and locally derived biogenic carbonates and are progressively being cemented by iron sulfides. Oxidation of hydrogen sulfide produces locally acidic conditions that corrode the adjacent limestones. Potential sources of S, H2S, Fe, Ba, and Sr are discussed. ?? 1987.

  15. Establishing criteria to distinguish oil- from methane-seep carbonates

    NASA Astrophysics Data System (ADS)

    Smrzka, Daniel; Zwicker, Jennifer; Bach, Wolfgang; Bohrmann, Gerhard; Peckmann, Jörn

    2016-04-01

    Hydrocarbon seeps harbor biota depending on chemosynthesis that is preserved in the fossil record as part of authigenic carbonate deposits. Seep environments are characterized by emanation of methane-rich fluids, yet an increasing number of seeps have been discovered in recent years that are typified by seepage of crude oil. Fluid composition is an important factor governing the composition and diversity of seep-dwelling fauna at modern seeps, as different species have differing tolerances and requirements with regard to the emitted compounds. In this regard, oil seepage has a profound influence on the diversity and distribution of seep-endemic macrofauna and microbial communities. Despite current efforts to better understand oil seeps and their ecology, the confident identification of oil seeps in the geologic record still poses fundamental problems. We present new geochemical data that allow for a more reliable identification of oil seepage during the Phanerozoic. Clear, fibrous aragonite cements of modern and putative ancient oil- and methane-seep deposits were analyzed for their rare earth element (REE) content. This cement is common in seep limestones and represents a product of the anaerobic oxidation of methane and higher hydrocarbons. Clear aragonite is particularly pure and virtually free of detrital inclusions, making it an ideal mineral for comparative geochemical analyses. Its REE composition reveals that oil-seep deposits are significantly enriched in REEs compared to methane- seep deposits. Furthermore, bulk total organic carbon (TOC) measurements suggest that modern and putative ancient oil seep carbonates are enriched in organic carbon. The combined data serve as a promising tool for identifying oil seepage in the fossil record. Our results provide the foundation for an improved understanding of the adaptation of chemosynthesis-based life to oil as an energy source.

  16. Oil and gas seeps within Absaroka volcanics of northwestern Wyoming

    SciTech Connect

    Sundell, K.A.; Love, J.D.

    1986-08-01

    Three new occurrences of asphaltic, liquid, and gaseous hydrocarbons have been discovered in the southeastern Absaroka Range. These petroleum seeps are 40 to 110 mi southeast of previously known seeps within Eocene volcaniclastic rocks at Calcite Springs, Tower Junction, and Sweetwater Mineral Springs, Wyoming. The Middle Fork seep and Castle Rocks seep are near the headwaters of the Middle and North Forks of Owl Creek, respectively. The Chimney Rock asphalt locality is along the South Fork of the Wood River. Water samples from the Middle Fork seep fluoresce greenish-orange and contain 6 to 8 mg/L of extractable bituminous hydrocarbons. An iridescent oily film forms on the water surface and on abundant gas bubbles trapped within moss. The Castle Rocks seep, in Quaternary gravels along the bed of the North Fork of Owl Creek, shows iridescent oily bubbles in emerging spring water and black, sooty lenses of carbon-coated gravels in overlying dry deposits. The Middle Fork and Castle Rocks seeps rise through thin Quaternary deposits overlying the Aycross Formation (Eocene). The Chimney Rock asphalt locality is in a northwest-trending paleovalley fill consisting of highly deformed masses of volcanic strata in the Tepee Trail and Wiggins Formations. Thin (< 1 in. thick), discontinuous, subvertical veins of asphaltum cut through these rocks. These petroleum seeps demonstrate migration of hydrocarbons after the volcaniclastic strata were emplaced and suggest that significant petroleum resources may occur elsewhere within Eocene volcaniclastic rocks and/or within Mesozoic and Paleozoic reservoirs beneath the volcanics.

  17. {Polycyclic aromatic hydrocarbons (PAHs) and aliphatic hydrocarbons in gas and particle phases in two sites of Mexico: MILAGRO project}

    NASA Astrophysics Data System (ADS)

    Amador-Muñoz, O.; Villalobos-Pietrini, R.; Castro, T.; Gaspariano-Larino, R.

    2009-04-01

    Aliphatic hydrocarbons are markers of anthropogenic and biogenic emission sources1; meanwhile PAHs are generated by incomplete combustion sources2. The last ones are important compounds due to their carcinogenic and mutagenic properties3,4. The aim of this study was to identify and quantify aliphatic hydrocarbons and PAHs in gas and particles phases of the atmospheric aerosol and to determine the day and night time behavior during the MILAGRO (Megacity Initiative: Local Global and Research Observations) campaign. The gas phase was collected on polyurethane foam, while particles less than 2.5 m (PM2.5) were collected on glass fiber filters covered with Teflon (TIGF, pallflex) of 8x10 in. Samplings were carried out with a high volume sampler (Tisch) with a flow of 1.13 m3 min-1 at two sites: Instituto Mexicano del Petróleo (T0) and Tecamac (T1) located at North and Northeast of Mexico City, respectively during day (7:00 am-7:00 pm) and night time (7:00 pm-7:00 am) from 1 to 29 of March, 2006. Ninteen PAHs and 23 aliphatic hydrocarbons from n-C13H28 to n-C35H72 were analyzed by gas chromatography coupled to mass spectrometry in impact mode. The samples were spiked with deuterads PAHs and aliphatics hydrocarbons before ultrasound extraction. Medians comparisons were made with Mann-Whitney U test. PAHs with molecular weight (MW) less than 228 g mol-1 were distributed in the gas phase, in both sites. Higher concentrations of PAHs ≥ 228 g mol-1 in PM2.5, were observed during night period (p

  18. Influence of parasitism in controlling the health, reproduction and PAH body burden of petroleum seep mussels

    NASA Astrophysics Data System (ADS)

    Powell, Eric N.; Barber, Robert D.; Kennicutt, Mahlon C., II; Ford, Susan E.

    1999-12-01

    Petroleum seep mussels are often exposed to high hydrocarbon concentrations in their natural habitat and, thus, offer the opportunity to examine the relationship between parasitism, disease and contaminant exposure under natural conditions. This is the first report on the histopathology of cold-seep mussels. Seep mussels were collected by submersible from four primary sites in the Gulf of Mexico, lease blocks Green Canyon (GC) 184, GC-234, GC-233, and Garden Banks 425 in 550-650 m water depth. Five types of parasites were identified in section: (1) gill "rosettes" of unknown affinity associated with the gill bacteriocytes, (2) gill "inclusions" similar to chlamydia/rickettsia inclusions, (3) extracellular gill ciliates, (4) body "inclusions" that also resemble chlamydial/rickettsial inclusions, and (5) Bucephalus-like trematodes. Comparison to shallow-water mytilids demonstrates that: (1) both have similar parasite faunas; (2) seep mytilids are relatively heavily parasitized; and (3) infection intensities are extremely high in comparison to shallow-water mytilids for Bucephalus and chlamydia/rickettsia. In this study, the lowest prevalence for chlamydia/rickettsia was 67%. Prevalences of 100% were recorded from three populations. Bucephalus prevalence was ⩾70% in three of 10 populations. The parasite fauna was highly variable between populations. Some important parasites were not observed in some primary sites. Even within primary sites, some important parasites were not observed in some populations. Bucephalus may exert a significant influence on seep mussel population dynamics. Forty percent of the populations in this study are severely reproductively compromised by Bucephalus infection. Only a fraction of petroleum seep mussel populations are maintaining the entire beta-level population structure of this species. Variation in two parasites, gill ciliates and Bucephalus, explained most of the variation in PAH body burden between mussel populations. PAHs are

  19. Interaction between hydrocarbon seepage, chemosynthetic communities and bottom water redox at cold seeps of the Makran accretionary prism: insights from habitat-specific pore water sampling and modeling

    NASA Astrophysics Data System (ADS)

    Fischer, D.; Sahling, H.; Nöthen, K.; Bohrmann, G.; Zabel, M.; Kasten, S.

    2011-09-01

    The interaction between fluid seepage, bottom water redox, and chemosynthetic communities was studied at cold seeps across one of the world's largest oxygen minimum zones (OMZ) located at the Makran convergent continental margin. Push cores were obtained from seeps within and at the lower boundary of the core-OMZ with a remotely operated vehicle. Extracted pore water was analyzed for sulfide and sulfate contents. Depending on oxygen availability, seeps were either colonized by microbial mats or by mats and macrofauna. The latter, including ampharetid polychaetes and vesicomyid clams, occurred in distinct benthic habitats which were arranged in a concentric fashion around gas orifices. At most sites colonized by microbial mats, hydrogen sulfide was exported into the bottom water. Where macrofauna was widely abundant, hydrogen sulfide was consumed within the sediment. Numerical modeling of pore water profiles was performed in order to assess rates of fluid advection and bioirrigation. While the magnitude of upward fluid flow decreased from 11 cm yr-1 to <1 cm yr-1 and the sulfate/methane transition zone (SMTZ) deepened with increasing distance from the central gas orifice, the fluxes of sulfate into the SMTZ did not significantly differ (6.6-9.3 mol m-2 yr-1). Depth-integrated rates of bioirrigation increased from 162 cm yr-1 in central habitats characterized by microbial mats and sparse macrofauna to 348 cm yr-1 in habitats of large and small vesicomyid clams. These results reveal that chemosynthetic macrofauna inhabiting the outer seep habitats at the lower boundary of the OMZ efficiently bioirrigate and thus transport sulfate into the upper 10 to 15 cm of the sediment. In this way bioirrigation compensates for the lower upward flux of methane in outer habitats and stimulates rates of anaerobic oxidation of methane (AOM) with sulfate high enough to provide sulfide for chemosynthesis. Through bioirrigation macrofauna engineer their geochemical environment and fuel

  20. Interaction between hydrocarbon seepage, chemosynthetic communities, and bottom water redox at cold seeps of the Makran accretionary prism: insights from habitat-specific pore water sampling and modeling

    NASA Astrophysics Data System (ADS)

    Fischer, D.; Sahling, H.; Nöthen, K.; Bohrmann, G.; Zabel, M.; Kasten, S.

    2012-06-01

    The interaction between fluid seepage, bottom water redox, and chemosynthetic communities was studied at cold seeps across one of the world's largest oxygen minimum zones (OMZ) located at the Makran convergent continental margin. Push cores were obtained from seeps within and below the core-OMZ with a remotely operated vehicle. Extracted sediment pore water was analyzed for sulfide and sulfate concentrations. Depending on oxygen availability in the bottom water, seeps were either colonized by microbial mats or by mats and macrofauna. The latter, including ampharetid polychaetes and vesicomyid clams, occurred in distinct benthic habitats, which were arranged in a concentric fashion around gas orifices. At most sites colonized by microbial mats, hydrogen sulfide was exported into the bottom water. Where macrofauna was widely abundant, hydrogen sulfide was retained within the sediment. Numerical modeling of pore water profiles was performed in order to assess rates of fluid advection and bioirrigation. While the magnitude of upward fluid flow decreased from 11 cm yr-1 to <1 cm yr-1 and the sulfate/methane transition (SMT) deepened with increasing distance from the central gas orifice, the fluxes of sulfate into the SMT did not significantly differ (6.6-9.3 mol m-2 yr-1). Depth-integrated rates of bioirrigation increased from 120 cm yr-1 in the central habitat, characterized by microbial mats and sparse macrofauna, to 297 cm yr-1 in the habitat of large and few small vesicomyid clams. These results reveal that chemosynthetic macrofauna inhabiting the outer seep habitats below the core-OMZ efficiently bioirrigate and thus transport sulfate down into the upper 10 to 15 cm of the sediment. In this way the animals deal with the lower upward flux of methane in outer habitats by stimulating rates of anaerobic oxidation of methane (AOM) with sulfate high enough to provide hydrogen sulfide for chemosynthesis. Through bioirrigation, macrofauna engineer their geochemical

  1. Hydrocarbon concentrations in the American oyster, Crassostrea virginica, in Laguna de Terminos, Campeche, Mexico

    SciTech Connect

    Gold-Bouchot, G.; Norena-Barroso, E.; Zapata-Perez, O.

    1995-02-01

    Laguna de Terminos is a 2,500 km{sup 2} coastal lagoon in the southern Gulf of Mexico, located between 18{degrees} 20` and 19{degrees} 00` N, and 91{degrees} 00` and 92{degrees} 20` W (Figure 1). It is a shallow lagoon, with a mean depth of 3.5 m and connected to the Gulf of Mexico through two permanent inlets, Puerto Real to the east and Carmen to the west. Several rivers, most of them from the Grijalva-Usumacinta basin (the largest in Mexico and second largest in the Gulf of Mexico), drain into the lagoon with a mean annual discharge of 6 X 10{sup 9} m{sup 3}/year. This lagoon has been studied systematically, and is probably one of the best known in Mexico. An excellent overview of this lagoon can be found in Yanez-Arancibia and Day. The continental shelf north of Terminos, the Campeche Bank, is the main oil-producing zone in Mexico with a production of about 2 X 10{sup 6} barrels/day. It is also the main shrimp producer in the southern Gulf, with a mean annual catch of 18,000 tonnes/year, which represents 38 to 50% of the national catch in the Gulf of Mexico. The economic importance of this region, along with its extremely high biodiversity, both in terms of species and habitats, has prompted the Mexican government to study the creation of a wildlife refuge around Terminos. Thus, it is very important to know the current levels of pollutants in this area, as a contribution to the management plan of the proposed protected area. This paper looks at hydrocarbon concentrations in oyster tissue. 14 refs., 3 figs., 21 tabs.

  2. Pollution by petroleum hydrocarbons in sediments from continental shelf of Tabasco State, Mexico

    SciTech Connect

    Botello, A.V.; Gonzalez, C.; Diaz, G. )

    1991-10-01

    The Wider Caribbean is potentially one of the largest oil producing areas in the world. Major petroleum production areas include Louisiana and Texas, USA; the Bay of Campeche, Mexico; Lake Maracaibo, Venezuela; and Gulf of Paria, Trinidad; all of which are classified as production accident high-risk zones. About 5 million of barrels are transported every day in the Caribbean, thus generating an intense tanker traffic. It has been estimated that oil discharges from tank washings within the Wider Caribbean could be as high as 7 million barrels/year. For all those reasons petroleum pollution is considered as the major environmental problem in the Wider Caribbean area and increasing day to day due to the use of petroleum as the main energy source. On the other hand, the continental shelf of Tabasco state actually represents one of the most productive areas for crude oil in the Gulf of Mexico. Sediments were collected from this area and analyzed for hydrocarbons.

  3. Upper Permian (Guadalupian) facies and their association with hydrocarbons - Permian basin, west Texas and New Mexico

    SciTech Connect

    Ward, R.F.; Kendall, C.G.S.C.; Harris, P.M.

    1986-03-01

    Outcrops of Guadalupian sedimentary rocks in the Permian basin of west Texas and southeastern New Mexico are a classic example of the facies relationships that span a carbonate shelf. In the subsurface, these rocks form classic hydrocarbon-facies taps. Proceeding from basin to the updip termination of the shelf, the facies are (1) deep-water basin, (2) an apron of allochthonous carbonates, (3) carbonate shelf margin or reef, (4) carbonate sand flats, (5) carbonate barrier islands, (6) lagoon, and (7) coastal playas and supratidal salt flats (sabkhas). Over a half century of exploration drilling has shown that hydrocarbons in the Permian rocks of the Permian basin have accumulated at the updip contact of the lagoonal dolomites and clastics with the coastal evaporites, and in the basinal channel-fill clastics. The shelf marginal (reef) facies contain cavernous porosity, but commonly are water saturated. These facies relationships and hydrocarbon occurrences provide an exploration model with which to explore and rank hydrocarbon potential in other carbonate provinces. 16 figures, 3 tables.

  4. Spatial scales of bacterial community diversity at cold seeps (Eastern Mediterranean Sea).

    PubMed

    Pop Ristova, Petra; Wenzhöfer, Frank; Ramette, Alban; Felden, Janine; Boetius, Antje

    2015-06-01

    Cold seeps are highly productive, fragmented marine ecosystems that form at the seafloor around hydrocarbon emission pathways. The products of microbial utilization of methane and other hydrocarbons fuel rich chemosynthetic communities at these sites, with much higher respiration rates compared with the surrounding deep-sea floor. Yet little is known as to the richness, composition and spatial scaling of bacterial communities of cold seeps compared with non-seep communities. Here we assessed the bacterial diversity across nine different cold seeps in the Eastern Mediterranean deep-sea and surrounding seafloor areas. Community similarity analyses were carried out based on automated ribosomal intergenic spacer analysis (ARISA) fingerprinting and high-throughput 454 tag sequencing and were combined with in situ and ex situ geochemical analyses across spatial scales of a few tens of meters to hundreds of kilometers. Seep communities were dominated by Deltaproteobacteria, Epsilonproteobacteria and Gammaproteobacteria and shared, on average, 36% of bacterial types (ARISA OTUs (operational taxonomic units)) with communities from nearby non-seep deep-sea sediments. Bacterial communities of seeps were significantly different from those of non-seep sediments. Within cold seep regions on spatial scales of only tens to hundreds of meters, the bacterial communities differed considerably, sharing <50% of types at the ARISA OTU level. Their variations reflected differences in porewater sulfide concentrations from anaerobic degradation of hydrocarbons. This study shows that cold seep ecosystems contribute substantially to the microbial diversity of the deep-sea. PMID:25500510

  5. Spatial scales of bacterial community diversity at cold seeps (Eastern Mediterranean Sea)

    PubMed Central

    Pop Ristova, Petra; Wenzhöfer, Frank; Ramette, Alban; Felden, Janine; Boetius, Antje

    2015-01-01

    Cold seeps are highly productive, fragmented marine ecosystems that form at the seafloor around hydrocarbon emission pathways. The products of microbial utilization of methane and other hydrocarbons fuel rich chemosynthetic communities at these sites, with much higher respiration rates compared with the surrounding deep-sea floor. Yet little is known as to the richness, composition and spatial scaling of bacterial communities of cold seeps compared with non-seep communities. Here we assessed the bacterial diversity across nine different cold seeps in the Eastern Mediterranean deep-sea and surrounding seafloor areas. Community similarity analyses were carried out based on automated ribosomal intergenic spacer analysis (ARISA) fingerprinting and high-throughput 454 tag sequencing and were combined with in situ and ex situ geochemical analyses across spatial scales of a few tens of meters to hundreds of kilometers. Seep communities were dominated by Deltaproteobacteria, Epsilonproteobacteria and Gammaproteobacteria and shared, on average, 36% of bacterial types (ARISA OTUs (operational taxonomic units)) with communities from nearby non-seep deep-sea sediments. Bacterial communities of seeps were significantly different from those of non-seep sediments. Within cold seep regions on spatial scales of only tens to hundreds of meters, the bacterial communities differed considerably, sharing <50% of types at the ARISA OTU level. Their variations reflected differences in porewater sulfide concentrations from anaerobic degradation of hydrocarbons. This study shows that cold seep ecosystems contribute substantially to the microbial diversity of the deep-sea. PMID:25500510

  6. Predicting hydrocarbon potential of an earth formation underlying a body of water by analysis of seeps containing low concentrations of methane

    SciTech Connect

    Demaison, G.J.; Kaplan, I.R.

    1982-07-20

    The present invention provides for on-site capture of methane at sea, for isotopic examination. Liquid and interfering gases are separated from the methane; the methane is oxidized to form carbon dioxide and water; and the carbon dioxide and water are isotopically analyzed for carbon and deuterium distribution to determine methane origin, as an aid to evaluation of hydrocarbon potential of an earth formation.

  7. Predicting hydrocarbon potential of an earth formation underlying a body of water by analysis of seeps containing low concentrations of methane using improved cryogenic entrapment

    SciTech Connect

    Demaison, G.J.; Kaplan, I.R.

    1987-04-21

    Method is described of on-site collection and examination of microliter concentrations of methane in sea water so as to predict hydrocarbon potential of an earth formation, the formation containing a hydrocarbon pool that is the source of the methane, the method comprising: (i) at known geographic locations, continuously sampling the sea water at a selected depth; (ii) continuously vacuum separating the collected sea water into liquid and gas phases; (iii) continuously monitoring the gas phase of the sea water for hydrocarbons; (iv) quantitatively separating methane in the gas phase of step (iii) from interfering gas species also in the gas phase of step (iii) in the presence of an air carrier vented to the atmosphere and flowing at a known flow rate; (v) quantitatively oxidizing the methane of step (iv) to carbon dioxide and water vapor and then cryogenically trapping out the resulting carbon dioxide and water vapor in the presence of the air carrier, using a bed of granules maintained at dry ice temperature and composed of an inert, porous organic polymer cross-linked to form a lattice network of high surface area for retention of the carbon dioxide without phase change and for trapping out of the water vapor by freezing; and (vi) isotopically examining the carbon and deuterium distribution of the carbon dioxide and water vapor of step (v) so as to determine biogenic and/or thermogenic origin of the methane.

  8. Sequence stratigraphy as key to evolution of hydrocarbon prospects: Examples from northern Gulf of Mexico

    SciTech Connect

    Sullivan, N.H. ); Lowrie, A.

    1990-09-01

    Sequence stratigraphy is the study of rock relationships within a chronostratigraphic framework. Sequence stratigraphy is a guide to hydrocarbon prospect description and prediction. An individual sequence is a conformable succession of related strata bounded by major unconformities and corresponds to a 3rd order cycle, generally with a periodicity of a million or so years. successions of Within a sequence are parasequences, conformable related beds or bed-sets bounded by unconformities and corresponding to a 4th order cycle, with a periodicity ranging from 20 k to 100 k years. Their physical reality is based on Milankovitch climate cycles. As used here, the lateral distribution of strata and bed is global. In the northern Gulf of Mexico, an individual prospect probably formed over a period of 105 years. A hydrocarbon play, such as the Flexure Trend, evolved over a period of 10{sup 6} to 10{sup 7} years. A compilation of potential hydrocarbon trap types has been assembled for the Louisiana offshore, from coastal plain to lower slope. These potential traps are listed according to paleophysiographic provinces: coastal plain, shelf, shelf-break, upper slope, middle slope, and lower slope. Characteristics of each trap type are tabulated. The characteristics include: tectonics, regional and local sedimentation rates and types, position within an evolving sequence as determined by sequence stratigraphy, duration of reservoir and/or trap creation, and sea-level position. Regional geologic processes, such as salt tectonics, and approximate rates at which they operate are also listed. Exploration designations such as hydrocarbon province, play, and prospect may be correlated with continental margin wedge, sequence (strata), and parasequence (bed), respectively.

  9. Predicting hydrocarbon potential of an earth formation underlying a body of water by analysis of seeps containing low concentrations of carbonaceous gases

    SciTech Connect

    Orinda, G.J.; Kaplan, I.R.

    1986-03-04

    A method is described of on-site collection and examination of small concentrations of methane dissolved in water so as to predict hydrocarbon potential of an earth formation underlying a body of water, the formation being a source of methane. The method consists of: (a) at a known geographic location, continuously sampling the water at a selected flow rate and at a selected depth; (b) continuously vacuum separating the water into liquid and gas phases; (c) quantitatively separating interfering gas species from the methane at a series of separating stations by conveying the separated gas phase of step (b) via an air carrier vented to atmosphere and flowing at a known flow rate, in seriation to and through the separating stations; the separation at the separating stations including the substeps of: (i) removing water vapor and molecular carbon dioxide from the passing gas phase in the presence of the air carrier; (ii) oxidizing any carbon monoxide to carbon dioxide; (iii) trapping the carbon dioxide of step (ii); and (iv) cryogenically trapping out all low-, mid-, and high-range molecular weight hydrocarbons above C/sub 1/; (d) quantitatively oxidizing the methane in the gas phase at an oxidizing station without significant isotopic fractionation occurring; (e) cryogenically trapping the gaseous oxidant of step (d) in the form of carbon dioxide at a trapping station without significant isotopic fractionation occurring; and (f) isotopically analyzing the trapped oxidant of step (e) for carbon distribution so as to determine biogenic and/or thermogenic origin of the methane and thereby aid in the evaluation of the hydrocarbon potential of the earth formation.

  10. Exploratory study of particle-bound polycyclic aromatic hydrocarbons in different environments of Mexico City

    NASA Astrophysics Data System (ADS)

    Velasco, Erik; Siegmann, Philip; Siegmann, Hans C.

    2004-09-01

    Several studies regarding particulate matter in air pollution have been performed in Mexico City, but none have focused on environment exposure to particle-bound polycyclic aromatic hydrocarbons (PPAH), which are related to the occurrence of cardiopulmonary diseases and mortality. On this account, this study presents measurements of personal exposure to PPAH in different outdoor and indoor environments, as well as along roadways in Mexico City. The measurements were done with portable sensors based on photoelectric charging and diffusion charging to determine the PPAH concentrations and the joint active surface of all particles, respectively. The use of these two sensors in parallel is a useful tool to qualitatively identify the major sources and to describe the physical and chemical characteristics of the particles. The highest exposures were found in ambient air near traffic sources, mainly at sites with great influence of diesel vehicles, such as urban transfer bus stations. Roadway measurements showed that Mexican PPAH pollution levels are between those in large cities in Europe and USA. For indoor environments such as residences, shopping centers, restaurants and hospitality venues, it was found that secondhand smoke is the major contributor, however badly calibrated pilot stoves, inefficient ventilation and faulty air-conditioning systems can be additional sources of PPAH.

  11. Particulate polycyclic aromatic hydrocarbon spatial variability and aging in Mexico City

    NASA Astrophysics Data System (ADS)

    Thornhill, D. A.; Herndon, S. C.; Onasch, T. B.; Wood, E. C.; Zavala, M.; Molina, L. T.; Gaffney, J. S.; Marley, N. A.; Marr, L. C.

    2007-11-01

    As part of the Megacities Initiative: Local and Global Research Observations (MILAGRO) study in the Mexico City Metropolitan Area in March 2006, we measured particulate polycyclic aromatic hydrocarbons (PAHs) and other gaseous species and particulate properties at six locations throughout the city. The measurements were intended to support the following objectives: to describe spatial and temporal patterns in PAH concentrations, to gain insight into sources and transformations of PAHs, and to quantify the relationships between PAHs and other pollutants. Total particulate PAHs at the Instituto Mexicano del Petróleo (T0 supersite) located near downtown averaged 50 ng m-3, and aerosol active surface area averaged 80 mm2 m-3. PAHs were also measured on board the Aerodyne Mobile Laboratory, which visited six sites encompassing a mixture of different land uses and a range of ages of air parcels transported from the city core. Weak intersite correlations suggest that local sources are important and variable and that exposure to PAHs cannot be represented by a single regional-scale value. The relationships between PAHs and other pollutants suggest that a variety of sources and ages of particles are present. Among carbon monoxide, nitrogen oxides (NOx), and carbon dioxide, particulate PAHs are most strongly correlated with NOx. Mexico City's PAH-to-black carbon mass ratio of 0.01 is similar to that found on a freeway loop in the Los Angeles area and approximately 8-30 times higher than that found in other cities. Ratios also indicate that primary combustion particles are rapidly coated by secondary aerosol in Mexico City. If so, the lifetime of PAHs may be prolonged if the coating protects them against photodegradation or heterogeneous reactions.

  12. Comprehensive Chemical Characterization of Hydrocarbons in NIST Standard Reference Material 2779 Gulf of Mexico Crude Oil.

    PubMed

    Worton, David R; Zhang, Haofei; Isaacman-VanWertz, Gabriel; Chan, Arthur W H; Wilson, Kevin R; Goldstein, Allen H

    2015-11-17

    Comprehensive chemical information is needed to understand the environmental fate and impact of hydrocarbons released during oil spills. However, chemical information remains incomplete because of the limitations of current analytical techniques and the inherent chemical complexity of crude oils. In this work, gas chromatography (GC)-amenable C9-C33 hydrocarbons were comprehensively characterized from the National Institute of Standards and Technology Standard Reference Material (NIST SRM) 2779 Gulf of Mexico crude oil by GC coupled to vacuum ultraviolet photoionization mass spectrometry (GC/VUV-MS), with a mass balance of 68 ± 22%. This technique overcomes one important limitation faced by traditional GC and even comprehensive 2D gas chromatography (GC×GC): the necessity for individual compounds to be chromatographically resolved from one another in order to be characterized. VUV photoionization minimizes fragmentation of the molecular ions, facilitating the characterization of the observed hydrocarbons as a function of molecular weight (carbon number, NC), structure (number of double bond equivalents, NDBE), and mass fraction (mg kg(-1)), which represent important metrics for understanding their fate and environmental impacts. Linear alkanes (8 ± 1%), branched alkanes (11 ± 2%), and cycloalkanes (37 ± 12%) dominated the mass with the largest contribution from cycloalkanes containing one or two rings and one or more alkyl side chains (27 ± 9%). Linearity and good agreement with previous work for a subset of >100 components and for the sum of compound classes provided confidence in our measurements and represents the first independent assessment of our analytical approach and calibration methodology. Another crude oil collected from the Marlin platform (35 km northeast of the Macondo well) was shown to be chemically identical within experimental errors to NIST SRM 2779, demonstrating that Marlin crude is an appropriate surrogate oil for researchers conducting

  13. Volatile liquid hydrocarbons in waters of the Gulf of Mexico and Caribbean Sea

    SciTech Connect

    Sauer, T.C. Jr.

    1980-03-01

    Concentrations of volatile liquid hydrocarbons (VLH), C/sub 6/-C/sub 14/ hydrocarbons, were determined in 1977 in coastal, shelf, and open-ocean surface waters of the Gulf of Mexico and Caribbean Sea. In open-ocean, nonpetroleum-polluted surface water, VLH concentrations were 60 ng.liter/sup -1/ while in heavily polluted Louisiana shelf and coastal water values reached 500 ng.liter/sup -1/. Caribbean surface samples had very low concentrations, 30 ng.liter/sup -1/. The relationship between anthropogenic gaseous hydrocarbons and VLH was approximately linear. Aromatic VLH accounted for 60 to 85% of the total VLH in surface waters. Cycloalkane concentrations were < 1.0 ng.liter/sup -1/ in open ocean water, 60 to 100 ng.liter/sup -1/ in polluted water (20% of total VLH). Alkanes were 15 ng.liter/sup -1/ in open ocean water, 40 ng.liter/sup -1/ in polluted water. The concentrations of five major VLH compounds (aromatics) in water samples - benzene, toluene, ethylbenzene, m/sup -/, p-xylenes, and o-xylene (called BTX) - were sufficient to predict the total VLH. The empirically determined relationship is VLH (ng.liter/sup -1/) = 1.42 BTX (ng.liter/sup -1/); r = 0.96. Subsurface VLH concentrations in samples of polluted waters collected from depths of 50 m were only 35 to 40 ng.liter/sup -1/ below surface concentrations. Open ocean subsurface samples had concentrations of only 30 ng.liter/sup -1/ at 30 to 50-m depths, comparable to those of Caribbean surface water.

  14. SHEEP CREEK SEEP CHARACTERIZATION

    EPA Science Inventory

    The materials presented represent an assessment of site conditions related to the LaCrone property seep, located in the NW 1/4 of Section 34, Township 7E, Range 2N, near Harden City, OK. The primary objective of the study was to identify possible source(s) for the saline water, ...

  15. Petrography and geochemistry of barite chimneys associated with hydrocarbon vents on the Gulf of Mexico slope

    SciTech Connect

    Fu, B.

    1995-10-01

    Barite chimneys up to 30 cm high were recently documented and recovered from hydrocarbon venting areas on the Louisiana Slope in the Gulf of Mexico in water depths of 510-520 m. The chimneys are dominated by barite (BaSO{sub 4}) associated with minor amounts of pyrite, iron oxide, Mg-calcite, and detrital silicates. The barites display distinct string-like and dendritic-like morphologies assembled from rosette assemblages that are typically 20 to 40 {mu}m in diameter. The interiors of chimneys, exhibit macroscopic growth layers 1 to 5 mm thick which alternate between dark-gray and light-yellow colors. Compared with barites from hydrothermal, marine, and continental settings, the Gulf of Mexico (GOM) barites are more enriched in Sr(average 15.5 mol% and maximum 30 mol%) and Ca(average 2.8 mol% and maximum 4.6 mol%). Backscatter images and electron microprobe traverse analyses indicate that most barite crystals exhibit rhythmic chemical zonations because of the variation of concentrations of Sr and Ca. The {delta}{sup 34}S(from 20.30 to 28.87{per_thousand}) and {delta}{sup 18}O(from 9.5 to 13.6{per_thousand}) of GOM barites suggest that the barite chimneys may form at or above the sediment-water interface from Ba-, Sr-, and Ca-rich formation fluids dissolving the underlying Jurassic-age salt and mixing with sulfate-rich seawater. Bacterial reduction of sulfate took place in the formation of some barite chimneys.

  16. Chronostratigraphic hydrocarbon plays and depositional styles in the northern Gulf of Mexico

    SciTech Connect

    Seni, S.J.; Brooke, J.; Marin, D.

    1995-10-01

    Sand-body reservoirs in the Federal OCS of the northern Gulf of Mexico were classified into 98 chronostratigraphic plays by style, structural style, and engineering parameters. Cumulative gas production is apportioned to three primary depositional styles: progradational (65%), submarine fan (16%), and aggradational (12%). In contrast, cumulative oil production is distributed primarily as progradational (58%), aggradational (23%), and submarine fan (16%). On the continental shelf, progradational environments are hydrocarbon rich owing to favorable sandstone-to-shale ratios and traps over salt structures and faulted anticlines. Submarine fan plays dominate downdip of the modern shelf edge. Remaining recoverable gas reserves for progradational (48%), submarine fan (28%), and aggradational (16%) reveal a decline of progradational plays and an increase of submarine fan plays. Average porosity varies between fan plays (26%), progradational plays (29%), and aggradational or retrogradational plays (28%) (statistical significance, 85% to 98%), in part as a function of play depth, which is greatest for submarine fan plays (11,631 ft). Average pay thickness of fan (45 ft) and retrogradational (34 ft) plays is higher than that of aggradational and progradational plays (31 ft) (statistical significance, 85% to 99%). Proved hydrocarbons are unequally distributed within chronozones in the Gulf. Forty-two percent of the original recoverable oil is concentrated in two chronozones-the lower Pleistocene Lenticulina 1 to Buliminella 1 (22.8%) and the upper Miocene Bigeneria A to Cristellaria K (20.4%). Gas is more uniformly distributed. Of the original recoverable gas, 29% exists in two chronozones-the lower Pleistocene Lenticulina 1 to Valvulina H (18.6%) and the upper Pleistocene Hyalinea balithica to Sangamon (10.6%). New discoveries will probably be made in submarine fan plays in Pleistocene to Miocene strata on the slope and in Miocene and older fan facies on the shelf.

  17. FUNGI AND HYDROCARBONS IN THE MARINE ENVIRONMENT

    EPA Science Inventory

    Hydrocarbons from various sources--anthropogenic pollution, marine seeps, marine algae, atmospheric fallout and terrestrial runoff--enter the ocean daily. These complex hydrocarbon mixtures are dispersed and degraded by abiotic and biogenic processes. Most commonly, bacteria are ...

  18. Succession of hydrocarbon-degrading bacteria in the aftermath of the deepwater horizon oil spill in the gulf of Mexico.

    PubMed

    Dubinsky, Eric A; Conrad, Mark E; Chakraborty, Romy; Bill, Markus; Borglin, Sharon E; Hollibaugh, James T; Mason, Olivia U; M Piceno, Yvette; Reid, Francine C; Stringfellow, William T; Tom, Lauren M; Hazen, Terry C; Andersen, Gary L

    2013-10-01

    The Deepwater Horizon oil spill produced large subsurface plumes of dispersed oil and gas in the Gulf of Mexico that stimulated growth of psychrophilic, hydrocarbon degrading bacteria. We tracked succession of plume bacteria before, during and after the 83-day spill to determine the microbial response and biodegradation potential throughout the incident. Dominant bacteria shifted substantially over time and were dependent on relative quantities of different hydrocarbon fractions. Unmitigated flow from the wellhead early in the spill resulted in the highest proportions of n-alkanes and cycloalkanes at depth and corresponded with dominance by Oceanospirillaceae and Pseudomonas. Once partial capture of oil and gas began 43 days into the spill, petroleum hydrocarbons decreased, the fraction of aromatic hydrocarbons increased, and Colwellia, Cycloclasticus, and Pseudoalteromonas increased in dominance. Enrichment of Methylomonas coincided with positive shifts in the δ(13)C values of methane in the plume and indicated significant methane oxidation occurred earlier than previously reported. Anomalous oxygen depressions persisted at plume depths for over six weeks after well shut-in and were likely caused by common marine heterotrophs associated with degradation of high-molecular-weight organic matter, including Methylophaga. Multiple hydrocarbon-degrading bacteria operated simultaneously throughout the spill, but their relative importance was controlled by changes in hydrocarbon supply. PMID:23937111

  19. Mobile laboratory measurements of black carbon, polycyclic aromatic hydrocarbons and other vehicle emissions in Mexico City

    NASA Astrophysics Data System (ADS)

    Jiang, M.; Marr, L. C.; Dunlea, E. J.; Herndon, S. C.; Jayne, J. T.; Kolb, C. E.; Knighton, W. B.; Rogers, T. M.; Zavala, M.; Molina, L. T.; Molina, M. J.

    2005-08-01

    Black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) are of concern due to their effects on climate and health. The main goal of this research is to provide the first estimate of emissions of BC and particle-phase PAHs (PPAHs) from motor vehicles in Mexico City. The emissions of other pollutants including carbon monoxide (CO), oxides of nitrogen (NOx), volatile organic compounds (VOCs), and particulate matter of diameter 2.5 µm and less (PM2.5) are also estimated. As a part of the Mexico City Metropolitan Area field campaign in April 2003 (MCMA-2003), a mobile laboratory was driven throughout the city. The laboratory was equipped with a comprehensive suite of gas and particle analyzers, including an aethalometer that measured BC and a photoionization aerosol sensor that measured PPAHs. While driving through traffic, the mobile lab is continuously sampling exhaust plumes from the vehicles around it. We have developed a method of automatically identifying exhaust plumes, which are then used as the basis for calculation of fleet-average emission factors. In the approximately 75 h of on-road sampling during the field campaign, we have identified ~30 000 exhaust measurement points that represent a variety of vehicle types and driving conditions. The large sample provides a basis for estimating fleet-average emission factors and thus the emission inventory. Motor vehicles in the Mexico City area are estimated to emit 1700±200 metric tons BC, 57±6 tons PPAHs, 1 190 000±40 000 tons CO, 120 000±3000 tons NOx, 202 000±4000 tons VOCs, and 4400±400 tons PM2.5 per year, not including cold start emissions. The estimates for CO, NOx, and PPAHs may be low by up to 10% due to the slower response time of analyzers used to measure these species. Compared to the government's official motor vehicle emission inventory for the year 2002, the estimates for CO, NOx, VOCs, and PM2.5 are 38% lower, 23% lower, 7% higher, and 26% higher, respectively. The distributions of

  20. Spatial and temporal variability of particulate polycyclic aromatic hydrocarbons in Mexico City

    NASA Astrophysics Data System (ADS)

    Thornhill, D. A.; de Foy, B.; Herndon, S. C.; Onasch, T. B.; Wood, E. C.; Zavala, M.; Molina, L. T.; Gaffney, J. S.; Marley, N. A.; Marr, L. C.

    2008-06-01

    As part of the Megacities Initiative: Local and Global Research Observations (MILAGRO) study in the Mexico City Metropolitan Area in March 2006, we measured particulate polycyclic aromatic hydrocarbons (PAHs) and other gaseous species and particulate properties, including light absorbing carbon or effective black carbon (BC), at six locations throughout the city. The measurements were intended to support the following objectives: to describe spatial and temporal patterns in PAH concentrations, to gain insight into sources and transformations of PAHs and BC, and to quantify the relationships between PAHs and other pollutants. Total particulate PAHs at the Instituto Mexicano del Petróleo (T0 supersite) located near downtown averaged 50 ng m-3, and aerosol active surface area averaged 80 mm2 m-3. PAHs were also measured on board the Aerodyne Mobile Laboratory, which visited six sites encompassing a mixture of different land uses and a range of ages of air parcels transported from the city core. A combination of analyses of time series, back trajectories, concentration fields, pollutant ratios, and correlation coefficients supports the concept of T0 as an urban source site, T1 as a receptor site with strong local sources, Pedregal and PEMEX as intermediate sites, Pico Tres Padres as a vertical receptor site, and Santa Ana as a downwind receptor site. Weak intersite correlations suggest that local sources are important and variable and that exposure to PAHs and BC cannot be represented by a single regional-scale value. The relationships between PAHs and other pollutants suggest that a variety of sources and ages of particles are present. Among carbon monoxide, nitrogen oxides (NOx), and carbon dioxide, particulate PAHs are most strongly correlated with NOx. Mexico City's PAH/BC mass ratio of 0.01 is similar to that found on a freeway loop in the Los Angeles area and approximately 8 30 times higher than that found in other cities. Evidence also suggests that primary

  1. Evolution and hydrocarbon potential of offshore Pinar Del Rio area, Southern Gulf of Mexico

    SciTech Connect

    Tenreyro-Perez, R.; Lopez-Rivera, J.G.; Fernandez-Carmona, J.; Lopez-Quintero, J.O.

    1996-09-01

    The evolution of Southeast Gulf of Mexico comprises three main periods: pre-orogenic, syn-orogenic and post-orogenic. During pre-orogenic time, from Lower Jurassic to Campanian, the stages are the rift of Pangaea and the thermal subsidence (or drift). In drift stage two domains interacted in the space; the carbonate platforms (Bahamas, Yucatan, Organos and others), and the deepwater basins. These fluctuations were dictated by the differential subsidence and horizontal displacements of basement blocks as well as by the eustatic movements of the ocean. The Organos platform, for example, was entirely drowned since Upper Jurassic and the sedimentation continued in deepwater environment. The collision between Great Antilles Volcanic Arc and the continental margins since Upper Cretaceous modeled the Cuban orogen. Here, the southern facies thrusted over the northern section with simultaneous strike-slip movements. The interaction suddenly ceased in Eocene. The source rock levels are considerably more frequent in the deepwater domain than in the platforms. The Lower and Upper Jurassic as well as Lower and Middle Cretaceous horizons contain very high levels of organic matter. The offshore seismic shows the transition from the thrusted belt to the foreland basin with a typical triangle zone configuration. Reservoirs are expected in the Cretaceous section covered by seals conformed by early foreland basin sediments of Upper Cretaceous-Paleocene age. Foothill structures has a great potential for hydrocarbon exploration.

  2. Hydrocarbon concentrations in sediments and clams (Rangia cuneata) in Laguna de Pom, Mexico

    SciTech Connect

    Alvarez-Legorreta, T.; Gold-Bouchot, G.; Zapata-Perez, O.

    1994-01-01

    Laguna de Pom is a coastal lagoon within the Laguna de Terminos system in southern Gulf of Mexico. It belongs to the Grijalva-Usumacinta basin, and is located between 18{degrees} 33{prime} and 18{degrees} 38{prime} north latitude and 92{degrees} 01{prime} and 92{degrees} 14{prime} west longitude, in the Coastal Plain physiographic Province of the Gulf. It is ellipsoidal and approximately 10 km long, with a surface area of 5,200 ha and a mean depth of 1.5 m. Water salinity and temperature ranges are 0 to 13 {per_thousand} and 25{degrees} to 31{degrees}C, respectively. Benthic macrofauna is dominated by bivalves such as the clams Rangia cuneata, R. flexuosa, and Polymesoda carolineana. These clams provide the basis of an artisanal fishery, which is the main economic activity in the region. The presence of several oil-processing facilities around the lagoon is very conspicuous, which together with decreasing yields has created social conflicts, with the fishermen blaming the mexican state oil company (PEMEX) for the decrease in the clam population. This work aims to determine if the concentration of hydrocarbons in the clams (R. cuneata) and sediments of Laguna de Pom are responsible for the declining clam fishery. 11 refs., 4 figs., 2 tabs.

  3. Hydrocarbons in Deep-Sea Sediments following the 2010 Deepwater Horizon Blowout in the Northeast Gulf of Mexico

    PubMed Central

    Romero, Isabel C.; Schwing, Patrick T.; Brooks, Gregg R.; Larson, Rebekka A.; Hastings, David W.; Ellis, Greg; Goddard, Ethan A.; Hollander, David J.

    2015-01-01

    The Deepwater Horizon (DWH) spill released 4.9 million barrels of oil into the Gulf of Mexico (GoM) over 87 days. Sediment and water sampling efforts were concentrated SW of the DWH and in coastal areas. Here we present geochemistry data from sediment cores collected in the aftermath of the DWH event from 1000 – 1500 m water depth in the DeSoto Canyon, NE of the DWH wellhead. Cores were analyzed at high-resolution (at 2 mm and 5 mm intervals) in order to evaluate the concentration, composition and input of hydrocarbons to the seafloor. Specifically, we analyzed total organic carbon (TOC), aliphatic, polycyclic aromatic hydrocarbon (PAHs), and biomarker (hopanes, steranes, diasteranes) compounds to elucidate possible sources and transport pathways for deposition of hydrocarbons. Results showed higher hydrocarbon concentrations during 2010-2011 compared to years prior to 2010. Hydrocarbon inputs in 2010-2011 were composed of a mixture of sources including terrestrial, planktonic, and weathered oil. Our results suggest that after the DWH event, both soluble and highly insoluble hydrocarbons were deposited at enhanced rates in the deep-sea. We proposed two distinct transport pathways of hydrocarbon deposition: 1) sinking of oil-particle aggregates (hydrocarbon-contaminated marine snow and/or suspended particulate material), and 2) advective transport and direct contact of the deep plume with the continental slope surface sediments between 1000-1200 m. Our findings underline the complexity of the depositional event observed in the aftermath of the DWH event in terms of multiple sources, variable concentrations, and spatial (depth-related) variability in the DeSoto Canyon, NE of the DWH wellhead. PMID:26020923

  4. Abyssal seep site cementation

    SciTech Connect

    Neumann, A.C.; Paull, C.K.; Commeau, R.; Commeau, J.

    1988-01-01

    The deepest submarine cements known so far occur along the 3,300-m deep base of the Florida escarpment and are associated with methane-bearing brine seeps, which emanate there. These deep Holocene carbonates, which occur as surficial and buried crusts, burrow fillings, and friable horizons, were sampled via ALVIN. The carbonates form irregular halos extending up to 20 m from seeps colonized by chemosynthetic fauna. Mussels, gastropods, and clams, the carbonate components of the community, produce a shell hash that is locally cemented by coarsely crystalline low-Mg calcite. Halos of palisade calcite are reminiscent of ancient examples of marine cements. Also present are carbonate hemipelagics cemented by micrite into crusts and burrow fillings. The degree of cementation varies from pervasive to light. Slabs of cemented crust up to 30 cm thick contrast with typical shallow crusts and exhibit irregular tops and smooth bottoms indicating different chemical gradients and pathways.

  5. Rare earth elements of seep carbonates: Indication for redox variations and microbiological processes at modern seep sites

    NASA Astrophysics Data System (ADS)

    Feng, Dong; Lin, Zhijia; Bian, Youyan; Chen, Duofu; Peckmann, Jörn; Bohrmann, Gerhard; Roberts, Harry H.

    2013-03-01

    At marine seeps, methane is microbially oxidized resulting in the precipitation of carbonates close to the seafloor. Methane oxidation leads to sulfate depletion in sediment pore water, which induces a change in redox conditions. Rare earth element (REE) patterns of authigenic carbonate phases collected from modern seeps of the Gulf of Mexico, the Black Sea, and the Congo Fan were analyzed. Different carbonate minerals including aragonite and calcite with different crystal habits have been selected for analysis. Total REE content (ΣREE) of seep carbonates varies widely, from 0.1 ppm to 42.5 ppm, but a common trend is that the ΣREE in microcrystalline phases is higher than that of the associated later phases including micospar, sparite and blocky cement, suggesting that ΣREE may be a function of diagenesis. The shale-normalized REE patterns of the seep carbonates often show different Ce anomalies even in samples from a specific site, suggesting that the formation conditions of seep carbonates are variable and complex. Overall, our results show that apart from anoxic, oxic conditions are at least temporarily common in seep environments.

  6. Estimates of salt dynamical motion and hydrocarbon trapping around a salt diapir in the Gulf of Mexico

    SciTech Connect

    Lerche, I.; Petersen, K.

    1996-12-31

    On the basis of lithology determinations assessed from seismic, together with the geological situation inferred around a salt structure in the Viosca Knoll region of the Gulf of Mexico, quantitative analysis of both salt and sediment motion, together with thermal effects and hydrocarbon kinetic modeling, would seem to imply that: the salt stock rose syndepositionally with sedimentation throughout Jurassic time, with the salt top maintained at the sediment/water interface; at Cretaceous time a competent chalk deposition terminated salt`s rise; and Miocene and later deposition raised the temperature regime around the salt so that hydrocarbon generation occurred from about 10 MYBP until present day, with the gas window being entered about 3--5 MYBP. A secondary target for hydrocarbon retention is the Jurassic sediments with the salt mushroom as a tight sealing cover, and the salt stock as a lateral updip boundary impeding migration. Downhole information to improve the likelihood of estimating economic reserves of liquid condensate or gas hydrocarbons for this diapir, and possibly others, includes: vitrinite reflectance with depth to better assess paleotemperatures; downhole temperatures (corrected) with depth, giving a better assessment of the local thermal anomaly with depth; fluid pressure measurements with depth, which provide information on fluid-flow through formations, together with inferred excess heating and maturation of sediments with time caused by lower than normal thermal conductivities; and TOC and Rock-Eval pyrolysis measurements with depth to estimate regional and local source potential for hydrocarbon production.

  7. The earliest mollusc dominated seep fauna from the Early Jurassic of Argentina

    NASA Astrophysics Data System (ADS)

    Kaim, Andrzej; Jenkins, Robert; Parent, Horacio; Garrido, Alberto; Moriya, Kazuhiro

    2015-04-01

    The earliest mollusc dominated seep fauna from the Early Jurassic of Argentina Andrzej Kaim, Robert G. Jenkins, Horacio Parent, Alberto C. Garrido The hydrocarbon seep deposits are known from Early Jurassic of Argentina since the report of Gomez-Perez (2003). The latter author identified very negative δ13C values (down to -33) and several fabrics typical for seep carbonates. Nevertheless she identified no macrofaunal assemblages apart from worm tubes. We re-visited the locality of Gomez-Perez (named here La Elina) and we were able to collect several molluscs associated with the seep carbonate. The most common and diversified are molluscs and worm tubes. We identified at least three species of gastropods, including the oldest-known species of neomphalids, lucinid and protobranch bivalves and numerous ammonoids. Unlike another known Early Jurassic seep from Oregon and the only Late Triassic seep (also from Oregon) there are no brachiopods associated with this seep. Therefore we consider the seep at La Elina as the oldest seep of modern aspect where the fauna is dominated by molluscs and not brachiopods.

  8. Tracking hydrocarbon plume transport and biodegradation at Deepwater Horizon.

    PubMed

    Camilli, Richard; Reddy, Christopher M; Yoerger, Dana R; Van Mooy, Benjamin A S; Jakuba, Michael V; Kinsey, James C; McIntyre, Cameron P; Sylva, Sean P; Maloney, James V

    2010-10-01

    The Deepwater Horizon blowout is the largest offshore oil spill in history. We present results from a subsurface hydrocarbon survey using an autonomous underwater vehicle and a ship-cabled sampler. Our findings indicate the presence of a continuous plume of oil, more than 35 kilometers in length, at approximately 1100 meters depth that persisted for months without substantial biodegradation. Samples collected from within the plume reveal monoaromatic petroleum hydrocarbon concentrations in excess of 50 micrograms per liter. These data indicate that monoaromatic input to this plume was at least 5500 kilograms per day, which is more than double the total source rate of all natural seeps of the monoaromatic petroleum hydrocarbons in the northern Gulf of Mexico. Dissolved oxygen concentrations suggest that microbial respiration rates within the plume were not appreciably more than 1 micromolar oxygen per day. PMID:20724584

  9. Macondo-1 well oil-derived polycyclic aromatic hydrocarbons in mesozooplankton from the northern Gulf of Mexico

    USGS Publications Warehouse

    Mitra, Siddhartha; Kimmel, David G.; Snyder, Jessica; Scalise, Kimberly; McGlaughon, Benjamin D.; Roman, Michael R.; Jahn, Ginger L.; Pierson, James J.; Brandt, Stephen B.; Montoya, Joseph P.; Rosenbauer, Robert J.; Lorenson, T.D.; Wong, Florence L.; Campbell, Pamela L.

    2012-01-01

    Mesozooplankton (>200 μm) collected in August and September of 2010 from the northern Gulf of Mexico show evidence of exposure to polycyclic aromatic hydrocarbons (PAHs). Multivariate statistical analysis revealed that distributions of PAHs extracted from mesozooplankton were related to the oil released from the ruptured British Petroleum Macondo-1 (M-1) well associated with the R/VDeepwater Horizon blowout. Mesozooplankton contained 0.03–97.9 ng g−1 of total PAHs and ratios of fluoranthene to fluoranthene + pyrene less than 0.44, indicating a liquid fossil fuel source. The distribution of PAHs isolated from mesozooplankton extracted in this study shows that the 2010 Deepwater Horizon spill may have contributed to contamination in the northern Gulf of Mexico ecosystem.

  10. The occurrence of NADPH-ferrihemoprotein reductase in Corbula caribea, from a natural oil seep at La Brea, Trinidad.

    PubMed

    Mohammed, Azad; Agard, John

    2004-04-01

    Corbula caribea is the most common non-polychaete macrofaunal organism identified at a large natural oil seep at La Brea in south Trinidad. It is hypothesized that these animals may possess (NADPH-ferrihemoprotein reductase) a component of the Mixed Function Oxygenase system (MFO), which may allow them to ameliorate the potentially deleterious effects resulting from exposure to the high levels of petroleum hydrocarbons within this environment. This study was designed to determine whether organisms from the seep site showed greater enzyme activity when compared to organisms from a non-seep reference site. NADPH-ferrihemoprotein reductase activity was determined by incubating 10 microm cryostat sections with nitro-blue tetrazolium. The reaction product was determined by visual assessment and quantified by measuring the relative mean stain intensity. The intense staining, indicative of enzyme activity was evident in the digestive epithelia of seep animals. Observations indicated that organisms from the seep showed more intense staining, indicating greater enzyme activity, when compared to animals from a non-seep reference site. The relative stain intensity of NADPH-ferrihemoprotein reductase determined for organisms from the seep was 61.30. This was significantly higher than the stain intensity determined for organisms from the non-seep reference site (7.11). This supported visual assessments, which suggested that the seep organisms showed higher enzyme activity than organisms from the non-seep site. The results suggest that NADPH-ferrihemoprotein reductase may be present in Corbula caribea from the seep site and not in those from the non-seep site. It is possible that this enzyme may contribute to these animals ability to tolerate chronic exposure to petroleum hydrocarbons and offer then a selective advantage for survival the seep environment. PMID:15041435

  11. Does the "sleeping Dragon" Really Sleep?: the Case for Continuous Long-Term Monitoring at a Gulf of Mexico Cold Seep Site

    NASA Astrophysics Data System (ADS)

    Wilson, R. M.; Lapham, L.; Farr, N.; Lutken, C.; MacDonald, I. R.; Macelloni, L.; Riedel, M.; Sleeper, K.; Chanton, J.

    2011-12-01

    Continuous porewater monitoring indicates that the methane flux away from exposed hydrate mounds can vary considerably over time. Recently, we retrieved a Pore Fluid Array instrument pack from a hydrate outcrop adjacent to a NEPTUNE Canada observatory node. The sampler was designed to continuously collect and store sediment pore fluids over the course of 9 months. On analysis, we observed a 35mM variation in methane concentrations corresponding with an abrupt shift in current direction at the site. Video and resistivity data have led to previous speculation that hydrate growth and dissolution/dissociation may be seasonally variable. Cumulatively, these findings suggest that the persistence of hydrate outcrops may be extremely dynamic, driven by fluctuations in physical conditions on short time scales. Short-term monitoring in the Gulf of Mexico within Mississippi Canyon lease block 118 (MC118), a known hydrate-bearing site, indicates that physical conditions even at these depths (~540-890m) may be highly variable. Pressure can vary within hours, and recorded temperature changes of ~1.5°C have been associated with passing storms. Moreover, increased particle abundance was observed at the site in 2007 suggesting that organic matter flux to the sediments may vary on the scale of months to years. These inputs have the potential to alter the chemical environment surrounding the hydrate, thereby affecting dissolution rates. Continuous, long-term observations of physical conditions at MC118 could provide information about the potential for natural perturbations to impact hydrate dynamics on the scale of weeks or even days necessary for assessing the long-term persistence of hydrate outcrops. Sleeping Dragon is a massive hydrate outcrop at MC118 that has been monitored since 2006. Three years ago, researchers returning to the site found it visibly diminished relative to previous observations. This apparent shift toward net dissolution of the mound may have been

  12. Detecting gas seeps in Arctic water areas using remote sensing data

    NASA Astrophysics Data System (ADS)

    Bondur, V. G.; Kuznetsova, T. V.

    2015-12-01

    We consider the specific features of remote registration of sources of natural hydrocarbon gas seeps in Arctic water areas to substantiate the possibility of aerospace monitoring of shelf zones prospective for hydrocarbons. The main characteristics of degassing sources and their manifestations at the surface and in the water column have been determined. The areas of the Arctic shelf with potential natural gas shows that can be detected through remote sensing have been identified. We analyze promising aerospace methods for the registration of gas shows in the sea and give examples of hydrocarbon gas seeps observed from space.

  13. Carbonate-cemented hardgrounds: a subtle indicator for seep activity offshore Humboldt Bay

    NASA Astrophysics Data System (ADS)

    Shapiro, R. S.; Bazard, D.

    2007-12-01

    Active hydrocarbon seeps are common in the accretionary prism of the Cascadia subduction zone. In Humboldt County, California, the prism is exposed at the surface as a series of fault-propagated anticlines trending NW-SE. Offshore of the town of Samoa, a northwest-plunging anticline is breached at approximately 40 meters water depth, allowing hydrocarbons to seep out to the seafloor (40.8° N, 124.25° W). The assumed microbial activity at the seep leads to the production of interstitial carbonate cements forming hardgrounds. Cementation is pervasive and blocks eroded from the seep area of the seabed are transported onshore during storm events. Blocks collected from the beach range from 3--40 centimeters across. The sediments of the blocks are palimpsest transgressive deposits composed mostly of immature fine sand, but ranging from very fine to rounded gravels 4 cm diameter. Cementation is not dependent on grain size as all of the sediment sizes are cemented. In rare void spaces, a concentric banding of cements is obvious. The interstitial cements preserve original sedimentary structures including graded beds and high-angle cross-beds. Centimeter-scale subspherical concretions occur on the undersides of some blocks. There is no disruption of bedding in contrast to other seeps where the expulsion of gas can create pockmarks, brecciation, and other disturbances. Unlike the better studied seeps farther south in the Eel River basin, the Samoa seeps do not seem to host a rich chemosynthetic fauna. Whole and (mostly) fragmented shells preserved by the cemented sands represent a typical benthic inner shelf community including Dendraster, Macoma, and Olivella. Burrows preserved in the sands are largely horizontal and 1--2 mm diameter. Seep carbonate-cemented hardgrounds are less well studied then the more obvious meter-scale 'chemoherm' deposits. However, they may be more prevalent in the rock record and provide a new proxy for locating ancient seeps and hydrocarbon

  14. Mexico.

    ERIC Educational Resources Information Center

    Semaan, Leslie

    The text explores Mexico's history, geography, art, religion, and lifestyles in the context of its complex economy. The text focuses on Mexico's economy and reasons for its current situation. Part I of this teaching unit includes: Teacher Overview, Why Study Mexico, Mexico Fact Sheet, Map of Mexico, the Land and Climate, History, Government,…

  15. Metagenomes from two microbial consortia associated with Santa Barbara seep oil.

    PubMed

    Hawley, Erik R; Malfatti, Stephanie A; Pagani, Ioanna; Huntemann, Marcel; Chen, Amy; Foster, Brian; Copeland, Alexander; del Rio, Tijana Glavina; Pati, Amrita; Jansson, Janet R; Gilbert, Jack A; Tringe, Susannah Green; Lorenson, Thomas D; Hess, Matthias

    2014-12-01

    The metagenomes from two microbial consortia associated with natural oils seeping into the Pacific Ocean offshore the coast of Santa Barbara (California, USA) were determined to complement already existing metagenomes generated from microbial communities associated with hydrocarbons that pollute the marine ecosystem. This genomics resource article is the first of two publications reporting a total of four new metagenomes from oils that seep into the Santa Barbara Channel. PMID:24958360

  16. Impact of hydrocarbons, PCBs and heavy metals on bacterial communities in Lerma River, Salamanca, Mexico: Investigation of hydrocarbon degradation potential.

    PubMed

    Brito, Elcia M S; De la Cruz Barrón, Magali; Caretta, César A; Goñi-Urriza, Marisol; Andrade, Leandro H; Cuevas-Rodríguez, Germán; Malm, Olaf; Torres, João P M; Simon, Maryse; Guyoneaud, Remy

    2015-07-15

    Freshwater contamination usually comes from runoff water or direct wastewater discharges to the environment. This paper presents a case study which reveals the impact of these types of contamination on the sediment bacterial population. A small stretch of Lerma River Basin, heavily impacted by industrial activities and urban wastewater release, was studied. Due to industrial inputs, the sediments are characterized by strong hydrocarbon concentrations, ranging from 2 935 to 28 430μg·kg(-1) of total polyaromatic hydrocarbons (PAHs). These sediments are also impacted by heavy metals (e.g., 9.6μg·kg(-1) of Cd and 246μg·kg(-1) of Cu, about 8 times the maximum recommended values for environmental samples) and polychlorinated biphenyls (ranging from 54 to 123μg·kg(-1) of total PCBs). The bacterial diversity on 6 sediment samples, taken from upstream to downstream of the main industrial and urban contamination sources, was assessed through TRFLP. Even though the high PAH concentrations are hazardous to aquatic life, they are not the only factor driving bacterial community composition in this ecosystem. Urban discharges, leading to hypoxia and low pH, also strongly influenced bacterial community structure. The bacterial bioprospection of these samples, using PAH as unique carbon source, yielded 8 hydrocarbonoclastic strains. By sequencing the 16S rDNA gene, these were identified as similar to Mycobacterium goodii, Pseudomonas aeruginosa, Pseudomonas lundensis or Aeromonas veronii. These strains showed high capacity to degrade naphthalene (between 92 and 100% at 200mg·L(-1)), pyrene (up to 72% at 100mg·L(-1)) and/or fluoranthene (52% at 50mg·L(-1)) as their only carbon source on in vitro experiments. These hydrocarbonoclastic bacteria were detected even in the samples upstream of the city of Salamanca, suggesting chronical contamination, already in place longer before. Such microorganisms are clearly potential candidates for hydrocarbon degradation in the

  17. Comparative study of vent and seep macrofaunal communities in the Guaymas Basin

    NASA Astrophysics Data System (ADS)

    Portail, M.; Olu, K.; Escobar-Briones, E.; Caprais, J. C.; Menot, L.; Waeles, M.; Cruaud, P.; Sarradin, P. M.; Godfroy, A.; Sarrazin, J.

    2015-09-01

    Understanding the ecological processes and connectivity of chemosynthetic deep-sea ecosystems requires comparative studies. In the Guaymas Basin (Gulf of California, Mexico), the presence of seeps and vents in the absence of a biogeographic barrier, and comparable sedimentary settings and depths offers a unique opportunity to assess the role of ecosystem-specific environmental conditions on macrofaunal communities. Six seep and four vent assemblages were studied, three of which were characterised by common major foundation taxa: vesicomyid bivalves, siboglinid tubeworms and microbial mats. Macrofaunal community structure at the family level showed that density, diversity and composition patterns were primarily shaped by seep- and vent-common abiotic factors including methane and hydrogen sulfide concentrations, whereas vent environmental specificities (higher temperature, higher metal concentrations and lower pH) were not significant. The type of substratum and the heterogeneity provided by foundation species were identified as additional structuring factors and their roles were found to vary according to fluid regimes. At the family level, seep and vent similarity reached at least 58 %. All vent families were found at seeps and each seep-specific family displayed low relative abundances (< 5 %). Moreover, 85 % of the identified species among dominant families were shared between seep and vent ecosystems. This study provides further support to the hypothesis of continuity among deep-sea seep and vent ecosystems.

  18. Preliminary Results from the ChevronTexaco Gulf of Mexico Gas Hydrates JIP: Hydrocarbon Gases in Sediments

    NASA Astrophysics Data System (ADS)

    Lorenson, T. D.; Dougherty, J. A.; Claypool, G. E.

    2005-12-01

    The Gulf of Mexico Gas Hydrates JIP, in collaboration with the U.S. Department of Energy, is investigating naturally occurring gas hydrates in the Gulf of Mexico. Our role in the JIP is to relate gas composition to gas hydrate formation and free gas deposits both in and out of the gas hydrate stability field. Pore water hydrocarbon gas composition in conjunction with chloride concentrations and geothermal gradients are important factors that dictate gas hydrate phase boundaries. During April and May 2005, cores were taken and subsampled for gases in lease blocks Atwater Valley 13 and 14 and Keathley Canyon 151. Sample types included sediment headspace gas, free gas derived from sediment gas exsolution, and gas exsolution from controlled degassing of pressurized cores. The gases measured both onboard and in shore-based labs were nitrogen, oxygen, hydrogen sulfide, carbon dioxide, and the hydrocarbons methane through hexane. Sediment gases at the Atwater Valley sites, where seafloor mounds and adjacent sediments were cored, strongly suggest a microbial source of methane, with very little thermogenic gas input. Methane concentrations in free gas ranged from about 96 to 99.9 percent, with the balance composed of carbon dioxide. Methane to ethane ratios are greater than 1,000 and often over 10,000 indicating a microbial gas source. Gases from cores at Keathley Canyon were similar to those at Atwater Valley, however deeper cores contained increasing concentrations of ethane, propane, and butane suggesting that low concentrations of thermogenic gases are present. At these sites in the Gulf of Mexico, the gas composition of sediment and free gas suggests that gas hydrate is composed mainly of methane, and that the gas hydrate is likely structure 1. Thus, models of gas hydrate occurrence in these areas need to consider methane hydrate.

  19. Active seeps, investment climate draw interest to Uganda

    SciTech Connect

    Patton, D.K.; Kashambuzi, R.; Rubondo, E.N.T.

    1995-05-01

    Production has not been established in Uganda, but the hydrocarbon generating capacity of its rift basin is clearly evident. Reports of oil seeps date to 1925 to observations by Wayland; who relates 52 hydrocarbon occurrences in and around Lake Albert. Although not all remain active, nine oil seeps in the rift basin are confirmed active at present. The Albertine graben, a part of the East African rift system, dominates the geology of Uganda. Other, larger basins of similar evolution in Africa include the Sirte basin and the Gulf of Suez basin. These prolific basins account for one third of Africa`s total reserves. The paper describes the geologic setting, reservoirs, source rocks, geologic seals, structures, exploration history, licenses available, and fiscal terms.

  20. Vehicle Traffic as a Source of Particulate Polycyclic Aromatic Hydrocarbon Exposure in the Mexico City Metropolitan Area

    PubMed Central

    MARR, LINSEY C.; GROGAN, LISA A.; WÖHRNSCHIMMEL, HENRY; MOLINA, LUISAT.; MOLINA, MARIO J.; SMITH, THOMAS J.; GARSHICK, ERIC

    2005-01-01

    Surface properties of aerosols in the Mexico City metropolitan area have been measured in a variety of exposure scenarios related to vehicle emissions in 2002, using continuous, real-time instruments. The objective of these experiments is to describe ambient and occupational particulate polycyclic aromatic hydrocarbon (PAH) concentrations associated with vehicular traffic and facilities using diesel vehicles. Median total particulate PAH concentrations along Mexico City’s roadways range from 60 to 910 ng m−3, averaged over a minimum of 1 h. These levels are approximately 5 times higher than concentrations measured in the United States and among the highest measured ambient values reported in the literature. The ratio of particulate PAH concentration to aerosol active surface area is much higher along roadways and in other areas of fresh vehicle emissions, compared to ratios measured at sites influenced more by aged emissions or noncombustion sources. For particles freshly emitted by vehicles, PAH and elemental carbon (EC) concentrations are correlated because they both originate during the combustion process. Comparison of PAH versus EC and active surface area concentrations at different locations suggests that surface PAH concentrations may diminish with particle aging. These results indicate that exposure to vehicle-related PAH emissions on Mexico City’s roadways may present an important public health risk. PMID:15180054

  1. Constraining silica diagenesis in methane-seep deposits

    NASA Astrophysics Data System (ADS)

    Smrzka, Daniel; Kraemer, Stephan; Zwicker, Jennifer; Birgel, Daniel; Fischer, David; Kasten, Sabine; Goedert, James; Peckmann, Jörn

    2015-04-01

    Silicified fossils and silicified early diagenetic carbonate minerals as well as authigenic silica phases are common in ancient seep limestones. Silicification of calcareous fossils facilitates the preservation of even fine details and is therefore of great interest to paleontologists, permitting a reliable taxonomic identification of the chemosynthesis-based taxa that lived at ancient hydrocarbon seeps. Four methane-seep limestones of Paleozoic, Mesozoic, and Cenozoic age with abundant silica phases are compared in this study; one, an Eocene seep deposit on the north shore of the Columbia River at Knappton, western Washington State, USA, is described for the first time. Its lithology and fabrics, negative δ13Ccarbonate values as low as -27.6‰, and 13C-depleted biomarkers of archaea involved in the anaerobic oxidation of methane (AOM) reveal that the carbonate rock formed at a methane seep. The background sediments of the studied Phanerozoic seep limestones contain abundant siliceous microfossils, radiolarian tests in case of the Late Carboniferous Dwyka Group deposits from Namibia and the Late Triassic Graylock Butte deposits from eastern Oregon (USA), diatom frustules in case of the Eocene Knappton limestone and an Oligocene seep deposit from the Lincoln Creek Formation (western Washington State, USA). These microfossils are regarded as the source of dissolved silica, causing silicification and silica precipitation. All seep limestones used in this study are characterized by very similar paragenetic sequences. Silicified fossils include brachiopods and worm tubes, silica cements include microquartz, fibrous microcrystalline silica, and megaquartz. The silica cements formed after the AOM-derived cements ceased to precipitate but before equant calcite spar formed. Numerical experiments using the computer code PHREEQC were conducted to test the hypothesis that (1) AOM increases the pH of pore waters and that (2) this pH increase subsequently mobilizes biogenic

  2. The polycyclic aromatic hydrocarbon degradation potential of Gulf of Mexico native coastal microbial communities after the Deepwater Horizon oil spill.

    PubMed

    Kappell, Anthony D; Wei, Yin; Newton, Ryan J; Van Nostrand, Joy D; Zhou, Jizhong; McLellan, Sandra L; Hristova, Krassimira R

    2014-01-01

    The Deepwater Horizon (DWH) blowout resulted in oil transport, including polycyclic aromatic hydrocarbons (PAHs) to the Gulf of Mexico shoreline. The microbial communities of these shorelines are thought to be responsible for the intrinsic degradation of PAHs. To investigate the Gulf Coast beach microbial community response to hydrocarbon exposure, we examined the functional gene diversity, bacterial community composition, and PAH degradation capacity of a heavily oiled and non-oiled beach following the oil exposure. With a non-expression functional gene microarray targeting 539 gene families, we detected 28,748 coding sequences. Of these sequences, 10% were uniquely associated with the severely oil-contaminated beach and 6.0% with the non-oiled beach. There was little variation in the functional genes detected between the two beaches; however the relative abundance of functional genes involved in oil degradation pathways, including polycyclic aromatic hydrocarbons (PAHs), were greater in the oiled beach. The microbial PAH degradation potentials of both beaches, were tested in mesocosms. Mesocosms were constructed in glass columns using sands with native microbial communities, circulated with artificial sea water and challenged with a mixture of PAHs. The low-molecular weight PAHs, fluorene and naphthalene, showed rapid depletion in all mesocosms while the high-molecular weight benzo[α]pyrene was not degraded by either microbial community. Both the heavily oiled and the non-impacted coastal communities showed little variation in their biodegradation ability for low molecular weight PAHs. Massively-parallel sequencing of 16S rRNA genes from mesocosm DNA showed that known PAH degraders and genera frequently associated with oil hydrocarbon degradation represented a major portion of the bacterial community. The observed similar response by microbial communities from beaches with a different recent history of oil exposure suggests that Gulf Coast beach communities are

  3. The polycyclic aromatic hydrocarbon degradation potential of Gulf of Mexico native coastal microbial communities after the Deepwater Horizon oil spill

    PubMed Central

    Kappell, Anthony D.; Wei, Yin; Newton, Ryan J.; Van Nostrand, Joy D.; Zhou, Jizhong; McLellan, Sandra L.; Hristova, Krassimira R.

    2014-01-01

    The Deepwater Horizon (DWH) blowout resulted in oil transport, including polycyclic aromatic hydrocarbons (PAHs) to the Gulf of Mexico shoreline. The microbial communities of these shorelines are thought to be responsible for the intrinsic degradation of PAHs. To investigate the Gulf Coast beach microbial community response to hydrocarbon exposure, we examined the functional gene diversity, bacterial community composition, and PAH degradation capacity of a heavily oiled and non-oiled beach following the oil exposure. With a non-expression functional gene microarray targeting 539 gene families, we detected 28,748 coding sequences. Of these sequences, 10% were uniquely associated with the severely oil-contaminated beach and 6.0% with the non-oiled beach. There was little variation in the functional genes detected between the two beaches; however the relative abundance of functional genes involved in oil degradation pathways, including polycyclic aromatic hydrocarbons (PAHs), were greater in the oiled beach. The microbial PAH degradation potentials of both beaches, were tested in mesocosms. Mesocosms were constructed in glass columns using sands with native microbial communities, circulated with artificial sea water and challenged with a mixture of PAHs. The low-molecular weight PAHs, fluorene and naphthalene, showed rapid depletion in all mesocosms while the high-molecular weight benzo[α]pyrene was not degraded by either microbial community. Both the heavily oiled and the non-impacted coastal communities showed little variation in their biodegradation ability for low molecular weight PAHs. Massively-parallel sequencing of 16S rRNA genes from mesocosm DNA showed that known PAH degraders and genera frequently associated with oil hydrocarbon degradation represented a major portion of the bacterial community. The observed similar response by microbial communities from beaches with a different recent history of oil exposure suggests that Gulf Coast beach communities are

  4. Observations of bubbles in natural seep flares at MC 118 and GC 600 using in situ quantitative imaging

    NASA Astrophysics Data System (ADS)

    Wang, Binbin; Socolofsky, Scott A.; Breier, John A.; Seewald, Jeffrey S.

    2016-04-01

    This paper reports the results of quantitative imaging using a stereoscopic, high-speed camera system at two natural gas seep sites in the northern Gulf of Mexico during the Gulf Integrated Spill Research G07 cruise in July 2014. The cruise was conducted on the E/V Nautilus using the ROV Hercules for in situ observation of the seeps as surrogates for the behavior of hydrocarbon bubbles in subsea blowouts. The seeps originated between 890 and 1190 m depth in Mississippi Canyon block 118 and Green Canyon block 600. The imaging system provided qualitative assessment of bubble behavior (e.g., breakup and coalescence) and verified the formation of clathrate hydrate skins on all bubbles above 1.3 m altitude. Quantitative image analysis yielded the bubble size distributions, rise velocity, total gas flux, and void fraction, with most measurements conducted from the seafloor to an altitude of 200 m. Bubble size distributions fit well to lognormal distributions, with median bubble sizes between 3 and 4.5 mm. Measurements of rise velocity fluctuated between two ranges: fast-rising bubbles following helical-type trajectories and bubbles rising about 40% slower following a zig-zag pattern. Rise speed was uncorrelated with hydrate formation, and bubbles following both speeds were observed at both sites. Ship-mounted multibeam sonar provided the flare rise heights, which corresponded closely with the boundary of the hydrate stability zone for the measured gas compositions. The evolution of bubble size with height agreed well with mass transfer rates predicted by equations for dirty bubbles.

  5. Marine cold seeps and their manifestations: geological control, biogeochemical criteria and environmental conditions

    NASA Astrophysics Data System (ADS)

    Suess, Erwin

    2014-10-01

    Characteristics of cold seeps at different geologic settings are the subject of this review primarily based on results of the Research Consortium SFB 574. Criteria are drawn from examples on the erosive convergent margin off Costa Rica, the accretionary margin off Chile supplemented by examples from the transform margin of the Golf of Cadiz and the convergent Hikurangi margin off New Zealand. Others are from well-studied passive margins of the Black Sea, the Golf of Mexico, the eastern Mediterranean Sea and the South China Sea. Seeps at all settings transport water and dissolved compounds to the ocean through the seafloor by different forcing mechanism and from different depths of the submerged geosphere (10s of meters to 10s of km). The compounds sustain oasis-type ecosystems by providing bioactive reductants sulfide, methane and hydrogen. Hereby, the interaction between fluid composition, flux rates and biota results in a diagnostic hydrocarbon-metazoan-microbe-carbonate association; currently, well over 100 active sites are known. The single most important reaction is microbially mediated anaerobic oxidation of methane with secondary reactions involving S-biogeochemistry and carbonate mineral precipitation. Seep fluids and their seafloor manifestations provide clues as to source depth, fluid-sediment/rock interaction during ascent, lifetime and cyclicity of seepage events but less so on the magnitude of return flow. At erosive margins, Cl-depleted and B-enriched fluids from clay dehydration provide criteria for source depth and temperature. The upward material flow generates mud volcanoes at the seafloor above the projected location of dehydration at depth. At accretionary margins, fluids are derived from more shallow depths by compaction of sediments as they ride on the incoming oceanic plate; they are emitted through thrust faults. At highly sedimented margins, organic-rich and evaporite-containing strata (when present) determine the final fluid composition

  6. Preliminary Analysis of Manual and Automated Seep Detection in Multibeam Water-Column Backscatter

    NASA Astrophysics Data System (ADS)

    McKenna, L.; Auner, L.; Weller, E.; Paton, M.; Doucet, M.; Lobecker, E.

    2014-12-01

    Identifying and locating gaseous seafloor seeps using multibeam sonar water-column backscatter is a growing interest in the scientific, energy, and resource management communities. Until recently, seeps were manually detected when viewing water-column backscatter returns in post-processing software. This manual procedure is time consuming and subjective. To examine this subjectivity, the NOAA Office of Exploration and Research conducted a quality control test using data collected during an expedition aboard the NOAA Ship Okeanos Explorer in the Gulf of Mexico from March to April, 2014. Water-column backscatter data was post-processed underway in FMMidwater and seep coordinates were manually geopicked from the beam fan. Ten percent of the original survey lines were independently re-processed using the same manual detection methods but with a different observer. Results show that manual seep selection can be highly variable between two different individuals. To help reduce this subjectivity and time required to manually detect seeps, QPS, Inc. developed a Feature Detection Tool for FMMidwater that uses an algorithm developed by the University of New Hampshire Center for Coastal and Ocean Mapping. To test the tool, the 10% subset of survey lines were run through the Feature Detection Tool using default settings, and the automatically detected seeps were compared with the manual geopicks. Not surprisingly, initial results show there can be variability between manual and algorithm seeps. Scrutiny of the automatic picks shows that the tool identified 60% of the seeps detected, and verified, by the independent manually-detecting observers. 32% of the seeps identified manually were missed by the tool, but 8% additional seeps were identified by the algorithm that had been missed through manual detection. The automatic detection showed several false positives, requiring manual intervention, but at a significantly lower level of effort than manual scrutinization of the raw

  7. Concentrations and sources of polycyclic aromatic hydrocarbons in surface coastal sediments of the northern Gulf of Mexico

    PubMed Central

    2014-01-01

    Background Coastal sediments in the northern Gulf of Mexico have a high potential of being contaminated by petroleum hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), due to extensive petroleum exploration and transportation activities. In this study we evaluated the spatial distribution and contamination sources of PAHs, as well as the bioavailable fraction in the bulk PAH pool, in surface marsh and shelf sediments (top 5 cm) of the northern Gulf of Mexico. Results PAH concentrations in this region ranged from 100 to 856 ng g−1, with the highest concentrations in Mississippi River mouth sediments followed by marsh sediments and then the lowest concentrations in shelf sediments. The PAH concentrations correlated positively with atomic C/N ratios of sedimentary organic matter (OM), suggesting that terrestrial OM preferentially sorbs PAHs relative to marine OM. PAHs with 2 rings were more abundant than those with 5–6 rings in continental shelf sediments, while the opposite was found in marsh sediments. This distribution pattern suggests different contamination sources between shelf and marsh sediments. Based on diagnostic ratios of PAH isomers and principal component analysis, shelf sediment PAHs were petrogenic and those from marsh sediments were pyrogenic. The proportions of bioavailable PAHs in total PAHs were low, ranging from 0.02% to 0.06%, with higher fractions found in marsh than shelf sediments. Conclusion PAH distribution and composition differences between marsh and shelf sediments were influenced by grain size, contamination sources, and the types of organic matter associated with PAHs. Concentrations of PAHs in the study area were below effects low-range, suggesting a low risk to organisms and limited transfer of PAHs into food web. From the source analysis, PAHs in shelf sediments mainly originated from direct petroleum contamination, while those in marsh sediments were from combustion of fossil fuels. PMID:24641695

  8. Impact of the Deepwater Horizon oil spill on bioavailable polycyclic aromatic hydrocarbons in Gulf of Mexico coastal waters

    PubMed Central

    Allan, Sarah E.; Smith, Brian W.; Anderson, Kim A.

    2012-01-01

    An estimated 4.1 million barrels of oil and 2.1 million gallons of dispersants were released into the Gulf of Mexico during the Deepwater Horizon oil spill. There is a continued need for information about the impacts and long-term effects of the disaster on the Gulf of Mexico. The objectives of this study were to assess bioavailable polycyclic aromatic hydrocarbons (PAHs) in the coastal waters of four Gulf Coast states that were impacted by the spill. For over a year, beginning in May 2010, passive sampling devices were used to monitor the bioavailable concentration of PAHs. Prior to shoreline oiling, baseline data were obtained at all the study sites, allowing for direct before and after comparisons of PAH contamination. Significant increases in bioavailable PAHs were seen following the oil spill, however, pre-oiling levels were observed at all sites by March, 2011. A return to elevated PAH concentrations, accompanied by a chemical fingerprint similar to that observed while the site was being impacted by the spill, was observed in Alabama in summer, 2011. Chemical forensic modeling demonstrated that elevated PAH concentrations are associated with distinctive chemical profiles. PMID:22321043

  9. Influence of the Deep Water Horizon Oil Spill on Atmospheric Hydrocarbon Levels over the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Blake, N. J.; Barletta, B.; Meinardi, S.; Leifer, I.; Rowland, F. S.; Blake, D. R.

    2010-12-01

    The waters of the Gulf of Mexico recently were impacted negatively by the large oil spill that occurred after an explosion at the BP Deep Water Horizon rig on April 20, 2010. In response to this disaster, and out of concern for the multitude of chemical pollutants being emitted, we collected 96 air samples in the Gulf region aboard the 65 ft vessel “R/V Eugenie” during 20-23 May, 2010. Sample analysis was by high sensitivity gas chromatographic analysis with special attention to the presence of possible toxic components. Analysis of each canister included straight-chain saturated hydrocarbons from C1 (methane) to C12 (dodecane), aromatic hydrocarbons such as benzene and toluene, as well as higher molecular weight species. High levels of C5-C12 alkanes and cyclo-alkanes, typical of crude oil, were observed in the atmosphere downwind of the spill location. However, the most soluble components, especially methane and benzene, were largely absent from the near-surface atmosphere implying dissolution in the deep sea, where they could impact negatively oxygen levels.

  10. Carbon isotope geochemistry of hydrocarbons in the Cerro Prieto geothermal field, Baja California Norte, Mexico

    NASA Technical Reports Server (NTRS)

    Des Marais, D. J.; Stallard, M. L.; Nehring, N. L.; Truesdell, A. H.

    1988-01-01

    Hydrocarbon abundances and stable-isotopic compositions were measured in wells M5, M26, M35 and M102, which represent a range of depths (1270-2000 m) and temperatures (275-330 degrees C) in the field. In order to simulate the production of the geothermal hydrocarbons, gases were collected from the pyrolysis of lignite in the laboratory. This lignite was obtained from a well which sampled rock strata which are identical to those occurring in the field, but which have experienced much lower subsurface temperatures. In both the well and the laboratory observations, high-temperature environments favored higher relative concentrations of methane, ethane and benzene and generally higher delta 13C-values in the individual hydrocarbons. The best correlation between the laboratory and well data is obtained when laboratory-produced gases from experiments conducted at lower (400 degrees C) and higher (600 degrees C) temperatures are mixed. This improved correlation suggests that the wells are sampling hydrocarbons produced from a spectrum of depths and temperatures in the sediments.

  11. Carbon isotope geochemistry of hydrocarbons in the Cerro Prieto geothermal field, Baja California Norte, Mexico

    USGS Publications Warehouse

    Des Marais, D.J.; Stallard, M.L.; Nehring, N.L.; Truesdell, A.H.

    1988-01-01

    Hydrocarbon abundances and stable-isotopic compositions were measured in wells M5, M26, M35 and M102, which represent a range of depths (1270-2000 m) and temperatures (275-330??C) in the field. In order to simulate the production of the geothermal hydrocarbons, gases were collected from the pyrolysis of lignite in the laboratory. This lignite was obtained from a well which sampled rock strata which are identical to those occurring in the field, but which have experienced much lower subsurface temperatures. In both the well and the laboratory observations, high-temperature environments favored higher relative concentrations of methane, ethane and benzene and generally higher ??13C-values in the individual hydrocarbons. The best correlation between the laboratory and well data is obtained when laboratory-produced gases from experiments conducted at lower (400??C) and higher (600??C) temperatures are mixed. This improved correlation suggests that the wells are sampling hydrocarbons produced from a spectrum of depths and temperatures in the sediments. ?? 1988.

  12. SeepC: Preliminary Characterization of Atlantic Margin Seep Ecosystems from Norfolk Canyon to New England Seep Sites.

    NASA Astrophysics Data System (ADS)

    Turner, P. J.; Ball, B.; Cole, E.; LaBella, A.; Wagner, J.; Van Dover, C. L.; Skarke, A. D.; Ruppel, C. D.

    2015-12-01

    Since 2013, more than 500 seep sites have been located along the continental margin of the eastern US using acoustic signals of gas plumes in the water column. During a July 2015 R/V Atlantis expedition, scientists used the submersible Alvin to explore seep sites at depths of 300 to 1500 m. Study sites ranged from Norfolk Canyon north to New England Seep 2 and included Baltimore, Veatch, and Shallop Canyon sites, as well as new unnamed sites between Norfolk and Baltimore Canyons. Mussels dominated the seep sites (cf ''Bathymodiolus'' childressi) but only small populations (<10s of individuals) were observed at seep sites associated with Shallop Canyon. B. heckerae, the dominant mussel at the Blake Ridge and Cape Fear seep sites (sites associated with salt diapirs off the Carolinas), appear to be present at only one of the Atlantic Margin seeps. At the Norfolk Canyon site, dead B. heckerae shells were observed and live individuals may be within the explored area. The abundant vesicomyid clam of Blake Ridge and Cape Fear sites was absent at the continental margin seeps. Apart from B. childressi, the most conspicuous megafaunal invertebrate species at the newly explored seeps was the red crab, Chaceon sp. and the rock crab, Cancer sp. These crabs are not seep endemic but they were especially abundant at the seeps and were observed to feed and mate on the seep grounds. Molecular tools will be used to explore the genetic structure of mussel populations from Norfolk to New England seeps, and stable isotope methods will be used to test for differences among sites in the source of carbon used by mussels. Alvin video transects and photo-mosaics will be used to collect data on macrofauna associated with seeps and to test the hypothesis that shallow seeps (300-500m) support more diverse assemblages than deep sites (1000-1500m).

  13. Geomicrobiological linkages between short-chain alkane consumption and sulfate reduction rates in seep sediments

    PubMed Central

    Bose, Arpita; Rogers, Daniel R.; Adams, Melissa M.; Joye, Samantha B.; Girguis, Peter R.

    2013-01-01

    Marine hydrocarbon seeps are ecosystems that are rich in methane, and, in some cases, short-chain (C2–C5) and longer alkanes. C2–C4 alkanes such as ethane, propane, and butane can be significant components of seeping fluids. Some sulfate-reducing microbes oxidize short-chain alkanes anaerobically, and may play an important role in both the competition for sulfate and the local carbon budget. To better understand the anaerobic oxidation of short-chain n-alkanes coupled with sulfate-reduction, hydrocarbon-rich sediments from the Gulf of Mexico (GoM) were amended with artificial, sulfate-replete seawater and one of four n-alkanes (C1–C4) then incubated under strict anaerobic conditions. Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist). Changes in the δ13C of all the alkanes in the reactors show enrichment over the course of the incubation, with the C3 and C4 incubations showing the greatest enrichment (4.4 and 4.5‰, respectively). The concurrent depletion in the δ13C of dissolved inorganic carbon (DIC) implies a transfer of carbon from the alkane to the DIC pool (−3.5 and −6.7‰ for C3 and C4 incubations, respectively). Microbial community analyses reveal that certain members of the class Deltaproteobacteria are selectively enriched as the incubations degrade C1–C4 alkanes. Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C3–C4 alkane-oxidizing sulfate-reducers. These data further constrain the potential influence of alkane oxidation on sulfate reduction rates (SRRs) in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial

  14. Presence of polycyclic aromatic hydrocarbons (PAHs) in apple in rural terrains from Mexico City.

    PubMed

    Salinas, Rutilio Ortiz; González, Gilberto Díaz; Bermudez, Beatriz Schettino; Tolentino, Rey Gutiérrez; Vega Y León, Salvador

    2010-08-01

    This paper describes PAH concentrations in apple crops that are growing in rural terrains in Mexico City. The concentrations of individual PAHs showed great variability, there being low and high molecular weight compounds in dry (high molecular weight for Tlahuac 7.06 microg/g and Milpa Alta 3.96 microg/g) and wet months (high molecular weight for Tlahuac 11.25 microg/g and Milpa Alta 12.05 microg/g). Some PAHs indicators and cross plot ratios Ant/(Ant + Phe) and Flu/(Flu + Pyr) define fossil fuels and vegetation combustion as the source of contamination over the cuticle of the apples. It is likely that deposition (dry and wet) is the principal source o f contamination over the apple surface. This study reveals the presence of PAHs in apples due to the high air contamination of Mexico City. PMID:20602085

  15. Non-methane hydrocarbons in the atmosphere of Mexico City: Results of the 2012 ozone-season campaign

    NASA Astrophysics Data System (ADS)

    Jaimes-Palomera, Mónica; Retama, Armando; Elias-Castro, Gabriel; Neria-Hernández, Angélica; Rivera-Hernández, Olivia; Velasco, Erik

    2016-05-01

    With the aim to strengthen the verification capabilities of the local air quality management, the air quality monitoring network of Mexico City has started the monitoring of selected non-methane hydrocarbons (NMHCs). Previous information on the NMHC characterization had been obtained through individual studies and comprehensive intensive field campaigns, in both cases restricted to sampling periods of short duration. This new initiative will address the NMHC pollution problem during longer monitoring periods and provide robust information to evaluate the effectiveness of new control measures. The article introduces the design of the monitoring network and presents results from the first campaign carried out during the first six months of 2012 covering the ozone-season (Mar-May). Using as reference data collected in 2003, results show reductions during the morning rush hour (6-9 h) in the mixing ratios of light alkanes associated with the consumption and distribution of liquefied petroleum gas and aromatic compounds related with the evaporation of fossil fuels and solvents, in contrast to olefins from vehicular traffic. The increase in mixing ratios of reactive olefins is of relevance to understand the moderate success in the ozone and fine aerosols abatement in recent years in comparison to other criteria pollutants. In the case of isoprene, the typical afternoon peak triggered by biogenic emissions was clearly observed for the first time within the city. The diurnal profiles of the monitored compounds are analyzed in terms of the energy balance throughout the day as a surrogate of the boundary layer evolution. Particular features of the diurnal profiles and correlation between individual NMHCs and carbon monoxide are used to investigate the influence of specific emission sources. The results discussed here highlight the importance of monitoring NMHCs to better understand the drivers and impacts of air pollution in large cities like Mexico City.

  16. Non-methane hydrocarbons in the atmosphere of Mexico City: Results of the 2012 ozone-season campaign

    NASA Astrophysics Data System (ADS)

    Jaimes-Palomera, Mónica; Retama, Armando; Elias-Castro, Gabriel; Neria-Hernández, Angélica; Rivera-Hernández, Olivia; Velasco, Erik

    2016-05-01

    With the aim to strengthen the verification capabilities of the local air quality management, the air quality monitoring network of Mexico City has started the monitoring of selected non-methane hydrocarbons (NMHCs). Previous information on the NMHC characterization had been obtained through individual studies and comprehensive intensive field campaigns, in both cases restricted to sampling periods of short duration. This new initiative will address the NMHC pollution problem during longer monitoring periods and provide robust information to evaluate the effectiveness of new control measures. The article introduces the design of the monitoring network and presents results from the first campaign carried out during the first six months of 2012 covering the ozone-season (Mar-May). Using as reference data collected in 2003, results show reductions during the morning rush hour (6-9 h) in the mixing ratios of light alkanes associated with the consumption and distribution of liquefied petroleum gas and aromatic compounds related with the evaporation of fossil fuels and solvents, in contrast to olefins from vehicular traffic. The increase in mixing ratios of reactive olefins is of relevance to understand the moderate success in the ozone and fine aerosols abatement in recent years in comparison to other criteria pollutants. In the case of isoprene, the typical afternoon peak triggered by biogenic emissions was clearly observed for the first time within the city. The diurnal profiles of the monitored compounds are analyzed in terms of the energy balance throughout the day as a surrogate of the boundary layer evolution. Particular features of the diurnal profiles and correlation between individual NMHCs and carbon monoxide are used to investigate the influence of specific emission sources. The results discussed here highlight the importance of monitoring NMHCs to better understand the drivers and impacts of air pollution in large cities like Mexico City.

  17. Disentangling oil weathering at a marine seep using GC x GC: broad metabolic specificity accompanies subsurface petroleum biodegradation.

    PubMed

    Wardlaw, George D; Arey, J Samuel; Reddy, Christopher M; Nelson, Robert K; Ventura, G Todd; Valentine, David L

    2008-10-01

    Natural seeps contribute nearly half of the oil entering the coastal ocean. However, environmental fate studies generally monitor fewer than 5% of these petroleum compounds. Hence, the rates and relevance of physical, chemical, and biological weathering processes are unknown for the large majority of hydrocarbons, both released from natural seeps and also from human activities. To investigate the specific compositional changes occurring in petroleum during subsurface degradation and submarine seepage, we studied the natural oil seeps offshore Santa Barbara, California with comprehensive, two-dimensional gas chromatography (GC x GC). With this technique, we quantified changes in the molecular diversity and abundance of hydrocarbons between subsurface reservoirs, a proximal sea floor seep, and the sea surface overlying the seep. We also developed methods to apportion hydrocarbon mass losses due to biodegradation, dissolution, and evaporation, for hundreds of tracked compounds that ascended from the subsurface to the sea floor to the sea surface. The results provide the first quantitative evidence of broad metabolic specificity for anaerobic hydrocarbon degradation in the subsurface and reveal new trends of rapid hydrocarbon evaporation at the sea surface. This study establishes GC x GC as a powerful technique for differentiating biological and physical weathering processes of complex mixtures at a molecular level. PMID:18939542

  18. Vehicle fleet emissions of black carbon, polycyclic aromatic hydrocarbons, and other pollutants measured by a mobile laboratory in Mexico City

    NASA Astrophysics Data System (ADS)

    Jiang, M.; Marr, L. C.; Dunlea, E. J.; Herndon, S. C.; Jayne, J. T.; Kolb, C. E.; Knighton, W. B.; Rogers, T. M.; Zavala, M.; Molina, L. T.; Molina, M. J.

    2005-12-01

    Black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) are of concern due to their effects on climate and health. The main goal of this research is to provide the first estimate of emissions of BC and particle-phase PAHs (PPAHs) from motor vehicles in Mexico City. The emissions of other pollutants including carbon monoxide (CO), oxides of nitrogen (NOx), volatile organic compounds (VOCs), and particulate matter of diameter 2.5 μm and less (PM2.5) are also estimated. As a part of the Mexico City Metropolitan Area field campaign in April 2003 (MCMA-2003), a mobile laboratory was driven throughout the city. The laboratory was equipped with a comprehensive suite of gas and particle analyzers, including an aethalometer that measured BC and a photoionization aerosol sensor that measured PPAHs. While driving through traffic, the mobile lab continuously sampled exhaust plumes from the vehicles around it. We have developed a method of automatically identifying exhaust plumes, which are then used as the basis for calculation of fleet-average emissions. In the approximately 75 h of on-road sampling during the field campaign, we have identified ~30 000 exhaust measurement points that represent a variety of vehicle types and driving conditions. The large sample provides a basis for estimating fleet-average emission factors and thus the emission inventory. Motor vehicles in the Mexico City area are estimated to emit 1700±200 metric tons BC, 57±6 tons PPAHs, 1 190 000±40 000 tons CO, 120 000±3000 tons NOx, 240 000±50 000 tons VOCs, and 4400±400 tons PM2.5 per year, not including cold start emissions. The estimates for CO, NOx, and PPAHs may be low by up to 10% due to the slower response time of analyzers used to measure these species. Compared to the government's official motor vehicle emission inventory for the year 2002, the estimates for CO, NOx, VOCs, and PM2.5 are 38% lower, 23% lower, 27% higher, and 25% higher, respectively. The distributions of emission

  19. Identification of Methanotrophic Biomarker Lipids in the Symbiont-Containing Gills of Seep Mussels

    NASA Technical Reports Server (NTRS)

    Jahnke, L. L.; Zahiralis, K. D.; Klein, H. P.; Morrison, David (Technical Monitor)

    1994-01-01

    Mussels collected from hydrocarbon seeps in the Gulf of Mexico grow with methane as sole carbon and energy source due to a symbiotic association with methane-oxidizing bacteria. Transmission electron micrographs of mussel gills show cells with stacked intracytoplasmic membranes similar to type I methanotrophic bacteria. Methanotrophs are known to synthesize several types of cyclic triterpenes, hopanoids and methyl sterols, as well as unique monounsaturated fatty acid, double bond positional isomers that serve as biomarkers for this group. Lipid analysis of dissected mussels demonstrated the presence of these biomarkers predominantly in the gill tissue with much smaller amounts in mantle and remaining body tissues. Gill tissue contained 1150 micrograms/g dry wt. of hopanepolyol derivatives and diplopterol while the mantle tissue contained only 17 micrograms/g. The C16 monounsaturated fatty acids (16:1) characteristic of type I methanotrophic membranes dominated the gill tissue making up 53% of the total while only 5% 16:1 was present in the mantle tissue. The methyl sterol distribution was more dispersed. The predominant sterol in all tissues was cholesterol with lesser amounts of other desmethyl and 4-methyl sterols. The gill and mantle tissues contained 3461 micrograms (17% methyl) and 2750 micrograms (5% methyl) sterol per gm dry wt., respectively. Methyl sterol accounted for 44% of the sterol esters isolated from the gill, suggesting active demethylation of the methanotrophic sterols in this tissue. The use of lipid biomarkers could provide an effective means for identifying host-symbiont relationships.

  20. Mexico

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This true-color image of Mexico was acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra spacecraft. In areal extent, Mexico is the third largest country on the continent of North America (not counting Greenland, which is a province of Denmark), comprised of almost 2 million square kilometers (756,000 square miles) of land. Home to roughly 100 million people, Mexico is second only to the United States in population, making it the world's largest Spanish-speaking nation. To the north, Mexico shares its border with the United States-a line that runs some 3,100 kilometers (1,900 miles) east to west. About half of this border is defined by the Rio Grande River, which runs southeast to the Gulf of Mexico (partially obscured by clouds in this image) and marks the dividing line between Texas and Mexico. Toward the upper left (northwest) corner of this image is the Baja California peninsula, which provides the western land boundary for the Gulf of California. Toward the northwestern side of the Mexican mainland, you can see the Sierra Madre Occidental Mountains (brownish pixels) running southeast toward Lake Chapala and the city of Guadalajara. About 400 km (250 miles) east and slightly south of Lake Chapala is the capital, Mexico City. Extending northward from Mexico City is the Sierra Madre Oriental Mountains, the irregular line of brownish pixels that seem to frame the western edges of the bright white cumulus clouds in this image. Between these two large mountain ranges is a large, relatively dry highland region. To the south, Mexico shares borders with Guatemala and Belize, both of which are located south of Mexico's Yucatan Peninsula. Image courtesy Reto Stockli, Brian Montgomery, and Robert Simmon, based on data from the MODIS Science Team

  1. (234)Th as a tracer of vertical transport of polycyclic aromatic hydrocarbons in the northern Gulf of Mexico.

    PubMed

    Adhikari, Puspa L; Maiti, Kanchan; Bosu, Somiddho; Jones, Patrick R

    2016-06-15

    Particle-mediated vertical flux of polycyclic aromatic hydrocarbons (PAHs) plays an important role in their removal from upper oceans and sets a limit on the amount delivered to the deep-sea sediments. In this study, we applied a one-dimensional steady-state (234)Th scavenging model to estimate vertical flux of PAHs in the northern Gulf of Mexico and compared them with sediment trap based flux estimates. The (234)Th-based ∑PAH43 fluxes were 6.7±1.0μgm(-2)d(-1) and 3.7±0.6μgm(-2)d(-1) while sediment trap-based fluxes were 4.0±0.6μgm(-2)d(-1) and 4.5±0.7μgm(-2)d(-1) at 150m and 250m, respectively. Alkylated homologues contributed to 80% of the total PAH fluxes which is in contrary to other regions where combustion derived parent PAHs dominate the fluxes. The results indicate that the (238)U-(234)Th disequilibria can be an effective tracer of particulate PAH fluxes in upper mesopelagic zones and can provide flux estimates with high spatial coverage needed to quantify their long term fate and transport in the marine systems. PMID:27090884

  2. Black carbon and polycyclic aromatic hydrocarbon emissions from vehicles in the United States-Mexico border region: pilot study.

    PubMed

    Kelly, Kerry; Wagner, David; Lighty, JoAnn; Quintero Núñez, Margarito; Vazquez, F Adrian; Collins, Kimberly; Barud-Zubillaga, Alberto

    2006-03-01

    The investigators developed a system to measure black carbon (BC) and particle-bound polycyclic aromatic hydrocarbon (PAH) emission factors during roadside sampling in four cities along the United States-Mexico border, Calexico/Mexicali and El Paso/Juarez. The measurement system included a photoacoustic analyzer for BC, a photoelectric aerosol sensor for particle-bound PAHs, and a carbon dioxide (CO2) analyzer. When a vehicle with measurable emissions passed the system probe, corresponding BC, PAH, and CO2 peaks were evident, and a fuel-based emission factor was estimated. A picture of each vehicle was also recorded with a digital camera. The advantage of this system, compared with other roadside methods, is the direct measurement of particulate matter components and limited interference from roadside dust. The study revealed some interesting trends: Mexican buses and all medium-duty trucks were more frequently identified as high emitters of BC and PAH than heavy-duty trucks or passenger vehicles. In addition, because of the high daily mileage of buses, they are good candidates for additional study. Mexican trucks and buses had higher average emission factors compared with U.S. trucks and buses, but the differences were not statistically significant. Few passenger vehicles had measurable BC and PAH emissions, although the highest emission factor came from an older model passenger vehicle licensed in Baja California. PMID:16573191

  3. Evidences of the Presence of Methane Seeps in the Colombian Caribbean Sea

    NASA Astrophysics Data System (ADS)

    Gracia, Adriana; Rangel-Buitrago, Nelson; Sellanes, Javier

    2010-05-01

    For the first time in the southern Caribbean Sea Margin of Colombia (between 450 - 700 m deep) we confirm the presence of methane seep communities near the deltas of the Magdalena and Sinu rivers. Some evidences of the occurrence of those communities include: i) bivalves constituents of marine chemosynthesis-based communities, which are indicators of reducing environments as vesicomyid and lucinid bivalves (Vesicomya caribbea, Calyptogena ponderosa, Ectenagena modioliforma, Lucinoma spp. and Graecina colombiensis), together with the rare solemyid clam Acharax caribbaea, ii) other seep-associated fauna such as the trochid snail Cataegis meroglypta, iii) the first report of vestimentiferan tubeworms for the area and, iv) the presence of authigenic carbonates; these constructions form hard substrates colonized by sessile fauna. Additionally, more than 20 species of benthic non-seep fauna were found associated in the area. The collected fauna exhibits an elevated taxonomic similarity to other modern and fossil seep communities from the Caribbean (Barbados Prism, Gulf of Mexico, Cenozoic seep taxa from Barbados, Trinidad and Venezuela). The presence of these chemosymbiotic species seems to be related to mud diapirism activity in the South West of the Colombian coast, this geologic characteristic indicates tectonic and depositional processes associated with the aforementioned deltas. Further research is necessary to establish biological and geological interactions, geochemical and geophysical controls, and organization of cold seeps communities in this unexplored area of the Caribbean. Keywords: Methane, Chemosynthesis-based communities,Bivalves, Mud diapirs, Colombian Caribbean Sea

  4. Mexico.

    PubMed

    1988-02-01

    Focus in this discussion of Mexico is on the following: geography; the people; history; political conditions; the economy; foreign relations; and relations between the US and Mexico. As of July 1987, the population of Mexico numbered 81.9 million with an estimated annual growth rate of 2.09%. 60% of the population is Indian-Spanish (mestizo), 30% American Indian, 9% white, and 1% other. Mexico is the most populous Spanish-speaking country in the world and the 2nd most populous country in Latin America. Education is decentralized and expanded. Mexico's topography ranges from low desert plains and jungle-like coastal strips to high plateaus and rugged mountains. Hernan Cortes conquered Mexico in 1919-21 and founded a Spanish colony that lasted for almost 300 years. Independence from Spain was proclaimed by Father Miguel Hidalgo on September 16, 1810; the republic was established on December 6, 1822. Mexico's constitution of 1917 provides for a federal republic with a separation of powers into independent executive, legislative, and judicial branches of government. Significant political themes of the administration of President Miguel de la Madrid Hurtado, who began his 6-year term in 1982, have been restructuring the economy, liberalizing trade practices, decentralizing government services, and eliminating corruption among public servants. In 1987, estimates put the real growth of the Mexican economy at 1.5%; the gross domestic product (GDP) had shrunk by 3.5% in 1986. Yet, on the positive side, Mexico's international reserves increased to record levels in 1987 (to about $15 billion), and its current account surplus reached more than $3 billion. Mexico has made considerable progress in moving to restructure its economy. It has substantially reduced impediments to international trade and has moved to reduce the number of parastatal firms. 1987 was the 2nd consecutive year in which Mexico recorded triple-digit inflation; inflation reached 158.8%. Other problems include

  5. Significance of aragonite cements around Cretaceous marine methane seeps

    SciTech Connect

    Savard, M.M.; Beauchamp, B.; Veizer, J.

    1996-05-01

    Detailed petrography and geochemistry of carbonate precipitates in Cretaceous cold seep mounds from the Canadian Arctic show spectacular early diagenetic products: some still-preserved splays and isopachous layers of fine, acicular aragonite, and large botryoids and crusts of low-magnesium calcite showing unusual entanglement of former fibrous calcite and aragonite. The latter mineralogy is suggested by clear, flat-terminated cathodoluminescence patterns interpreted as ancient crystal growth steps, and the former by rhombohedral terminations. The early cement phases very likely precipitated in cold Arctic water dominated by bicarbonates derived from bacterially oxidized methane: these cements have {delta}{sup 13}C values around {minus}44.0% and {delta}{sup 18}O values of 1.8 to 0.1% PDB. Coexistence of calcite and aragonite early cements in the Cretaceous seep mounds is unusual, because precipitation occurred in high-latitude, cold-water settings, and during a so-called calcite sea mode. As in modern marine hydrocarbon seeps, the chemistry of the Cretaceous system was apparently controlled by chemosynthetic bacterial activity, resulting in high a{sub HCO{sub 3}{sup {minus}}} that promoted precipitation of carbonates. The authors suggest that, locally, fluctuations in a{sub HCO{sub 3}{sup {minus}}}/a{sub SO{sub 4}{sup 2{minus}}} resulted in oscillating aragonite or calcite supersaturation, and hence, controlled the mineralogy of the early precipitates.

  6. Using production-based plays in the northern Gulf of Mexico as a hydrocarbon exploration tool

    SciTech Connect

    Lore, G.L.; Batchelder, E.C.

    1995-10-01

    The Minerals Management Service has described more than 100 plays in the northern Gulf of Mexico Outer Continental Shelf encompassing approximately 1,100 fields and over 9,500 productive sands. Plays are defined by a combination of production, chronostratigraphy, lighostratigraphy, and structural style. Cumulative production from these plays as of December 1993 is 9.01 billion barrels of oil and 107.7 trillion cubic feet of gas, with remaining proved reserves of 2.14 billion barrels of oil and 29.1 trillion cubic feet of gas. The information associated with these plays can be used by explorationists as a qualitative tool to target areas of potential exploration interest and as a quantitative tool to test the potential economic viability of both plays and individual prospects. Specific examples of each of these potential uses are provided. Qualitatively, the play maps target areas for future exploration in two ways. The first is to identify conceptual deep-sea fan plays located downdip from plays established in sediments of shallow water depositional environments. The second is to emphasize areas for both future exploration and infill potential around and within established plays. The extensive data sets associated with each play provide valuable quantitative information that can be used to assess the possible number and size of undiscovered accumulations in a play of exploration interest. At the individual prospect level, data related to reach productive sand and pool can be used to perform detailed geologic and economic evaluations.

  7. Distributions and accumulation rates of polycyclic aromatic hydrocarbons in the northern Gulf of Mexico sediments.

    PubMed

    Adhikari, Puspa L; Maiti, Kanchan; Overton, Edward B; Rosenheim, Brad E; Marx, Brian D

    2016-05-01

    Sediment samples collected from shelf, slope and interior basin of the northern Gulf of Mexico during 2011-2013, 1-3 years after the Deepwater Horizon (DWH) oil spill, were utilized to characterize PAH pollution history, in this region. Results indicate that the concentrations of surface ΣPAH43 and their accumulation rates vary between 44 and 160 ng g(-1) and 6-55 ng cm(-2) y(-1), respectively. ΣPAH43 concentration profiles, accumulation rates and Δ(14)C values are significantly altered only for the sediments in the immediate vicinity of the DWH wellhead. This shows that the impact of DWH oil input on deep-sea sediments was generally limited to the area close to the spill site. Further, the PAHs source diagnostic analyses suggest a noticeable change in PAHs composition from higher to lower molecular weight dominance which reflects a change in source of PAHs in the past three years, back to the background composition. Results indicate low to moderate levels of PAH pollution in this region at present, which are unlikely to cause adverse effects on benthic communities. PMID:26895564

  8. Comparison of two tunnel studies for non methane hydrocarbons in Mexico City

    SciTech Connect

    Mugica A, V.; Vega R, E.; Ruiz S, M.E.; Seila, R.

    1998-12-31

    Emissions from vehicles have long been considered a major source of pollutants involved in smog formation and ozone production. During the last few years, different control strategies have been taking place to reduce the high levels of ozone and some other atmospheric pollutants. Some of these strategies are: improvement of fuels, a program for compulsory vehicular emission test and the introduction of catalytic converters to be used in conjunction with unleaded gasoline since 1991. The comparison of the vehicular NMHC emission source profiles measured in a tunnel in Mexico City during March 1992 and May 1996 is presented. Samples were collected using stainless steel SUMMA{reg_sign} canisters and subsequent analyzed by gas chromatography with flame ionized detector. It was found that in general, the source profiles are similar, however, some differences were detected for some species. The sum of acetylene, ethylene and ethane contents, which are a typical combustion products, is lower for the 1996 source profile than for the 1992. In the same way, there is a small decrease of paraffin and olefin contents, except for hexane. Finally, significant differences were found for aromatic compounds, mainly toluene and xylenes which increased in 1996.

  9. Barite encrustation of benthic sulfur-oxidizing bacteria at a marine cold seep.

    PubMed

    Stevens, E W N; Bailey, J V; Flood, B E; Jones, D S; Gilhooly, W P; Joye, S B; Teske, A; Mason, O U

    2015-11-01

    Crusts and chimneys composed of authigenic barite are found at methane seeps and hydrothermal vents that expel fluids rich in barium. Microbial processes have not previously been associated with barite precipitation in marine cold seep settings. Here, we report on the precipitation of barite on filaments of sulfide-oxidizing bacteria at a brine seep in the Gulf of Mexico. Barite-mineralized bacterial filaments in the interiors of authigenic barite crusts resemble filamentous sulfide-oxidizing bacteria of the genus Beggiatoa. Clone library and iTag amplicon sequencing of the 16S rRNA gene show that the barite crusts that host these filaments also preserve DNA of Candidatus Maribeggiatoa, as well as sulfate-reducing bacteria. Isotopic analyses show that the sulfur and oxygen isotope compositions of barite have lower δ(34)S and δ(18)O values than many other marine barite crusts, which is consistent with barite precipitation in an environment in which sulfide oxidation was occurring. Laboratory experiments employing isolates of sulfide-oxidizing bacteria from Gulf of Mexico seep sediments showed that under low sulfate conditions, such as those encountered in brine fluids, sulfate generated by sulfide-oxidizing bacteria fosters rapid barite precipitation localized on cell biomass, leading to the encrustation of bacteria in a manner reminiscent of our observations of barite-mineralized Beggiatoa in the Gulf of Mexico. The precipitation of barite directly on filaments of sulfide-oxidizing bacteria, and not on other benthic substrates, suggests that sulfide oxidation plays a role in barite formation at certain marine brine seeps where sulfide is oxidized to sulfate in contact with barium-rich fluids, either prior to, or during, the mixing of those fluids with sulfate-containing seawater in the vicinity of the sediment/water interface. As with many other geochemical interfaces that foster mineral precipitation, both biological and abiological processes likely contribute

  10. A microbiological and biogeochemical investigation of the cold seep tubeworm Escarpia southwardae (Annelida: Siboglinidae): Symbiosis and trace element composition of the tube

    NASA Astrophysics Data System (ADS)

    Duperron, Sébastien; Gaudron, Sylvie M.; Lemaitre, Nolwenn; Bayon, Germain

    2014-08-01

    Tubeworms within the annelid family Siboglinidae rely on sulfur-oxidizing autotrophic bacterial symbionts for their nutrition, and are among the dominant metazoans occurring at deep-sea hydrocarbon seeps. Contrary to their relatives from hydrothermal vents, sulfide uptake for symbionts occurs within the anoxic subsurface sediment, in the posterior ‘root' region of the animal. This study reports on an integrated microbiological and geochemical investigation of the cold seep tubeworm Escarpia southwardae collected at the Regab pockmark (Gulf of Guinea). Our aim was to further constrain the links between the animal and its symbiotic bacteria, and their environment. We show that E. southwardae harbors abundant sulfur-oxidizing bacterial symbionts in its trophosome. Symbionts are able to fix inorganic carbon using the Calvin-Benson cycle, as reported in most other Siboglinidae, but can also use the reverse Tricarboxilic Acid Cycle. Surprisingly, the observed bacteria appear to be more closely related to symbionts of Escarpia and Lamellibrachia species from very distant sites located in the Gulf of Mexico and eastern Pacific, than to symbionts of a siboglinid occurring at a nearby methane seep site, only a few hundred km away from Regab. Then, by combining scanning electron microscopy and trace element (Mn, Fe, Sr, Zr) analyses of E. southwardae tube, we also show that two distinct oxidation fronts occur along the tube. The first one, near the posterior end of the tube, corresponds to the interface between oxic bottom waters and the underlying anoxic sediment. In contrast, the second redox front is located in the most anterior part of the tube, and could result from active oxygen uptake by the plume of the tubeworm. We speculate that intense oxygen consumption in this region could create favorable conditions for sulfate reduction by specialized bacteria associated with the plume, possibly leading to an additional source of dissolved sulfide that would further enhance

  11. Geologic framework, regional aquifer properties (1940s-2009), and spring, creek, and seep properties (2009-10) of the upper San Mateo Creek Basin near Mount Taylor, New Mexico

    USGS Publications Warehouse

    Langman, Jeff B.; Sprague, Jesse E.; Durall, Roger A.

    2012-01-01

    The U.S. Geological Survey, in cooperation with the U.S. Forest Service, examined the geologic framework, regional aquifer properties, and spring, creek, and seep properties of the upper San Mateo Creek Basin near Mount Taylor, which contains areas proposed for exploratory drilling and possible uranium mining on U.S. Forest Service land. The geologic structure of the region was formed from uplift of the Zuni Mountains during the Laramide Orogeny and the Neogene volcanism associated with the Mount Taylor Volcanic Field. Within this structural context, numerous aquifers are present in various Paleozoic and Mesozoic sedimentary formations and the Quaternary alluvium. The distribution of the aquifers is spatially variable because of the dip of the formations and erosion that produced the current landscape configuration where older formations have been exhumed closer to the Zuni Mountains. Many of the alluvial deposits and formations that contain groundwater likely are hydraulically connected because of the solid-matrix properties, such as substantive porosity, but shale layers such as those found in the Mancos Formation and Chinle Group likely restrict vertical flow. Existing water-level data indicate topologically downgradient flow in the Quaternary alluvium and indiscernible general flow patterns in the lower aquifers. According to previously published material and the geologic structure of the aquifers, the flow direction in the lower aquifers likely is in the opposite direction compared to the alluvium aquifer. Groundwater within the Chinle Group is known to be confined, which may allow upward migration of water into the Morrison Formation; however, confining layers within the Chinle Group likely retard upward leakage. Groundwater was sodium-bicarbonate/sulfate dominant or mixed cation-mixed anion with some calcium/bicarbonate water in the study area. The presence of the reduction/oxidation-sensitive elements iron and manganese in groundwater indicates reducing

  12. Genotoxicity in child populations exposed to Polycyclic Aromatic Hydrocarbons (PAHs) in the air from Tabasco, Mexico

    PubMed Central

    Gamboa, Rodríguez T.; Gamboa, Aldeco R.; Bravo, Alvarez H.; Ostrosky, Wegman P.

    2008-01-01

    The economy of the state of Tabasco is based on oil extraction. However, this imposes major effects to the environment and communities. Examples are the Polycyclic Aromatic Hydrocarbons (PAHs) that may be found in the soil, water and sediment of the region. Their volatility makes them available to living beings and results in genotoxic activity. The purpose of this study was to quantify the levels of PAHs in the air at several points in the state, and to analyze their relationship with possible damage to DNA on local inhabitants. Single Cell Gel Electrophoresis Assay (Comet Assay) was applied to peripheral blood lymphocytes of five groups of children between six and 15 years of age. PAH samples were analyzed following US/EPA TO-13-A method. Results indicated the presence in the air of most of the 16 PAHs considered as high priority by EPA, some of which have been reported with carcinogenic activity. Differences (p<0.05) were found between PAHs concentration in the gaseous component and in the particulate component of air samples, with the greatest values for the gaseous component. Greatest PAH concentrations were detected in areas with high oil extraction activities. Children groups from high oil activity areas presented genotoxic damage labeled from moderate to high according to DNA migration from nuclei (Tail Length: 14.2 – 42.14 μm and Tail/Head: 0.97 – 2.83 μm) compared with control group (12.25 and 0.63 μm, respectively). The group with greatest cell damage was located in the area with the greatest oil activity. We conclude that the presence of PAHs in the air may represent a health risk to populations that are chronically exposed to them at high oil activity regions. PMID:19151429

  13. Historical Distribution of Polycyclic Aromatic Hydrocarbons in Shallow Sediments from Lake Chapala, Mexico

    NASA Astrophysics Data System (ADS)

    Zárate-Del Valle, P. F.; Macías-Pérez, M. P.; Barajas-Martínez, C. D.; Gómez-Hermosillo, C. M.

    2008-12-01

    The incomplete combustion of fossil fuels and burning of vegetation and other organic materials release into the environment pollutants like polycyclic aromatic hydrocarbons (PAHs) which are ubiquitous pollutants. The environmental behavior of PAHs is characterized by very low solubility, high hydrophobic sorptive capacity (kow), low volatility and general chemical stability. These characteristics mean, in practice, that PAHs are environmentally persistent compounds that in aquatic systems, are strongly held to solid surfaces present as both suspended particles and bottom sediment. Additionally, because of their high partition to organic carbon, PAHs show a high rate of bioconcentration and an easy way to enter the food chain. A benthos type sediment core was collected (CHA-C: N20° 15.105'; W103° 03.104') from the depocenter of lake Chapala. The first 40 cm of the sedimentary column representing an ecological history of ~ 150 years (210Pb dating) were cutted every 2 cm (n=20). For each core sectioned, the presence of PAHs was evaluated by GC-MS following methods from the USEPA (EPA 3540C, EPA 3620C, EPA 8270C). For the first 30 cm deep only products resulting of PAHs degradation were identified, namely: Butilisobutilphtalate, 1,2-benzenedicarboxaldehyde, phenol and, cinnamaldehyde; we attibute the presence of these products to a faster transformation of PAHs by photo and metabolic degradation as well as to chemical oxydation. For the 30-40 cm deep, the presence of the follwing PAHs was detected: 1H-indene, 1,2- difluor-3,4,5-trimetylbenzenethylnaphthalene, naphthalene, anthracene, and phenantren. A study is in progress to determine the presence of PAHs in other sites of the lake. We conclude that shallow sediment (40 cm deep) from Lake Chapala could constitute a potentially large pool of PAHs.

  14. Opposing seasonal trends for polycyclic aromatic hydrocarbons and PM10: Health risk and sources in southwest Mexico City

    NASA Astrophysics Data System (ADS)

    Amador-Muñoz, Omar; Bazán-Torija, S.; Villa-Ferreira, S. A.; Villalobos-Pietrini, Rafael; Bravo-Cabrera, José Luis; Munive-Colín, Zenaida; Hernández-Mena, Leonel; Saldarriaga-Noreña, H.; Murillo-Tovar, M. A.

    2013-03-01

    This study reports the measurement of polycyclic aromatic hydrocarbons (PAHs) in airborne particles ≤ 10 μm (PM10) during four years. Seasonal variation was observed for PM10 and PAH in southwest Mexico City, with major mass concentrations during the dry season (November-April). A non linear decreasing trend of PM10 was observed during this period, while a linear increase (in the four years) was obtained for benzo[a]pyrene (88 pg m- 3), phenanthrene (29 pg m- 3), fluoranthene (88 pg m- 3), and benzo[ghi]perylene (438 pg m- 3). Coronene also showed an increasing trend but it was nonlinear. This suggests that air control strategies implemented by the government contributed to maintaining PM10 under the 24 h maximum limit and resulted in a decreasing trend during this period. However, these strategies did not result in controlling some organic constituents with mutagenic and/or carcinogenic properties as it is the case of benzo[a]pyrene. The annual average of this PAH exceeded the UK recommendation. It was estimated a median (10th-90th) lifetime health risk of 7.6 (3.4-17.2) additional cases of cancer per 10 million people in this zone exists and the health risk of PAH is almost three times greater in dry seasons than it is in rainy seasons. Specific humidity, temperature and wind speed acted as cleaners for PM10 and PAH from the atmosphere. PAH diagnostic ratios and correlation and principal component analyses suggest incomplete combustion from gasoline and diesel engines as the main contributor to PAH found in southwest Mexico City, where factor 1 grouped all PAH emitted from gasoline engines during first three years. During last year, factor 1 only grouped PAH markers of diesel engines. This suggests a change of emission amounts between gasoline and diesel combustion sources or a contribution of other source(s) which changed the PAH profiles. During four years retene was always separated from factors which grouped the rest of PAH, due to its wood combustion

  15. Mexico.

    PubMed

    1984-09-01

    Although Mexico has serious economic and population growth problems, the country is making progress toward solving both of these problems. Mexico has a population of 77.7 million and a population density of 102 persons/square mile. The country has a birth rate of 32/1000, a death rate of 6/1000, and an annual growth rate of 2.6%. The estimated infant mortality rate is 55/1000. The median age of the population is 17.4. Mexico City, with a population of 15 million, is the 3rd largest city in the world, and by 1995, it is expected to be the largest city in the world, with a projected population of 25.2 million. The government vigorously promotes family planning, and the annual population growth rate slowed down from a high of 3.2% in 1970-75 to the current rate of 2.6%. Mexico hopes to achieve replacement level fertility by the year 2000. Other government policies promote income equality, agricultural development, and regional equalization of population growth. In 1982 Mexico's per capita income was US$2270, exports totaled US$21 billion, and imports totaled US$15 billion. By 1976, Mexico's international debt was US$30.2 billion, and inflation was rampant. Recently, the newly elected president, Miguel de la Madrid of the Partido Revolucionario Institutional, obtained a grant of US$39 million from the International Monetary Fund and removed price controls. These efforts should help stabilize Mexico's economy. The country will also need to expand its exports and increase its cultivatable acreage. PMID:12339665

  16. Migrating Tundra Peregrine Falcons accumulate polycyclic aromatic hydrocarbons along Gulf of Mexico following Deepwater Horizon oil spill.

    PubMed

    Seegar, William S; Yates, Michael A; Doney, Gregg E; Jenny, J Peter; Seegar, Tom C M; Perkins, Christopher; Giovanni, Matthew

    2015-07-01

    Monitoring internal crude oil exposure can assist the understanding of associated risks and impacts, as well as the effectiveness of restoration efforts. Under the auspices of a long-term monitoring program of Tundra Peregrine Falcons (Falco peregrinus tundrius) at Assateague (Maryland) and South Padre Islands (Texas), we measured the 16 parent (unsubstituted) polycyclic aromatic hydrocarbons (PAHs), priority pollutants identified by the United States Environmental Protection Agency and components of crude oil, in peripheral blood cells of migrating Peregrine Falcons from 2009 to 2011. The study was designed to assess the spatial and temporal trends of crude oil exposure associated with the 2010 Deepwater Horizon (DWH) oil spill which started 20 April 2010 and was capped on 15 July of that year. Basal PAH blood distributions were determined from pre-DWH oil spill (2009) and unaffected reference area sampling. This sentinel species, a predator of shorebirds and seabirds during migration, was potentially exposed to residual oil from the spill in the northern Gulf of Mexico. Results demonstrate an increased incidence (frequency of PAH detection and blood concentrations) of PAH contamination in 2010 fall migrants sampled along the Texas Gulf Coast, declining to near basal levels in 2011. Kaplan-Meier peak mean ∑PAH blood concentration estimates varied with age (Juveniles-16.28 ± 1.25, Adults-5.41 ± 1.10 ng/g, wet weight) and PAHs detected, likely attributed to the discussed Tundra Peregrine natural history traits. Increased incidence of fluorene, pyrene and anthracene, with the presence of alkylated PAHs in peregrine blood suggests an additional crude oil source after DWH oil spill. The analyses of PAHs in Peregrine Falcon blood provide a convenient repeatable method, in conjunction with ongoing banding efforts, to monitoring crude oil contamination in this avian predator. PMID:25794559

  17. Gulf of Mexico continental slope study annual report, year 2. Volume 2. Primary volume. Interim report 1985-1986. [Sampling for hydrocarbons

    SciTech Connect

    Not Available

    1986-09-01

    This report, which was prepared in three volumes (Executive Summary, Primary Volume, and Appendix), details the findings of two years of sampling on the continental slope of the northern Gulf of Mexico at depths of 300-3000 m. Preliminary results from a third year of sampling are also presented. Physical and chemical measurements included: CTD casts at 35 stations; sediment characteristics, including hydrocarbons and bulk sediment parameters from 60 stations; tissue hydrocarbon levels of representative benthic organisms; and delta carbon-13 values from sediments and organisms, including comparison of areas of natural petroleum seepage to prevailing slope conditions. The biological oceanography section provides detailed enumeration of megafaunal specimens collected by trawling and of macro- and meiofaunal specimens collected with a 600 sq cm box core. Major megafaunal groups treated are Arthropoda, Echinodermata, and demersal fishes.

  18. Detection of Natural Oil Seeps in the Atlantic Ocean Using MODIS

    NASA Technical Reports Server (NTRS)

    Reahard, Ross; Jones, Jason B.; Mitchell, Mark

    2010-01-01

    Natural oil seepage is the release of crude oil into the ocean from fissures in the seabed. Oil seepage is a major contributor to the total amount of oil entering the world s oceans. According to a 2003 study by the National Academy of Sciences (NAS), 47 percent of oil entering the world s oceans is from natural seeps, and 53 percent is from human sources (extraction, transportation, and consumption). Oil seeps cause smooth oil slicks to form on the water s surface. Oil seeps can indicate the location of stores of fossil fuel beneath the ocean floor. Knowledge of the effect of oil seepage on marine life and marine ecosystems remains limited. In the past, remote sensing has been used to detect oil seeps in the Gulf of Mexico and off of the coast of southern California. This project utilized sun glint MODIS imagery to locate oil slicks off of the Atlantic coast, an area that had not previously been surveyed for natural oil seeps using remote sensing. Since 1982, the Atlantic Ocean has been closed to any oil and gas drilling. Recently, however, the U.S. Minerals Management Services (MMS) has proposed a lease for oil and gas drilling off the coasts of Virginia and North Carolina. Determining the location of seepage sites in the Atlantic Ocean will help MMS locate potential deposits of oil and natural gas, thereby reducing the risk of leasing areas for petroleum extraction that do not contain these natural resources.

  19. Comparative study of vent and seep macrofaunal communities in the Guaymas Basin

    NASA Astrophysics Data System (ADS)

    Portail, M.; Olu, K.; Escobar-Briones, E.; Caprais, J. C.; Menot, L.; Waeles, M.; Cruaud, P.; Sarradin, P. M.; Godfroy, A.; Sarrazin, J.

    2015-06-01

    Understanding the ecological processes and connectivity of chemosynthetic deep-sea ecosystems requires comparative studies. In the Guaymas Basin (Gulf of California, Mexico), the presence of seeps and vents in the absence of biogeographic barrier, comparable sedimentary settings and depths offers a unique opportunity to assess the role of ecosystem specific environmental conditions on macrofaunal communities. Six seep and four vent assemblages were studied, three of which were characterised by common major foundation taxa: vesicomyid bivalves, siboglinid tubeworms and microbial mats. Macrofaunal community structure at the family level showed that density, diversity and composition patterns were primarily shaped by seep and vent common abiotic factors including methane and hydrogen sulphide concentrations. The type of substratum and the heterogeneity provided by foundation species were identified as additional structuring factors and their roles were found to vary according to fluid regimes. Surprisingly, the presence of vent environmental specificities, with higher temperature, higher metal concentrations and lower pH was not significant in explaining community patterns. Moreover, Guaymas seep and vent shared an important number of common species suggesting frequent connections between the two ecosystems. Finally, this study provides further support for the hypothesis of continuity among deep-sea seep and vent ecosystems.

  20. Larvae from deep-sea methane seeps disperse in surface waters

    PubMed Central

    Arellano, Shawn M.; Van Gaest, Ahna L.; Johnson, Shannon B.; Vrijenhoek, Robert C.; Young, Craig M.

    2014-01-01

    Many species endemic to deep-sea methane seeps have broad geographical distributions, suggesting that they produce larvae with at least episodic long-distance dispersal. Cold-seep communities on both sides of the Atlantic share species or species complexes, yet larval dispersal across the Atlantic is expected to take prohibitively long at adult depths. Here, we provide direct evidence that the long-lived larvae of two cold-seep molluscs migrate hundreds of metres above the ocean floor, allowing them to take advantage of faster surface currents that may facilitate long-distance dispersal. We collected larvae of the ubiquitous seep mussel “Bathymodiolus” childressi and an associated gastropod, Bathynerita naticoidea, using remote-control plankton nets towed in the euphotic zone of the Gulf of Mexico. The timing of collections suggested that the larvae might disperse in the water column for more than a year, where they feed and grow to more than triple their original sizes. Ontogenetic vertical migration during a long larval life suggests teleplanic dispersal, a plausible explanation for the amphi-Atlantic distribution of “B.” mauritanicus and the broad western Atlantic distribution of B. naticoidea. These are the first empirical data to demonstrate a biological mechanism that might explain the genetic similarities between eastern and western Atlantic seep fauna. PMID:24827437

  1. Infaunal and megafaunal benthic community structure associated with cold seeps at the Vestnesa Ridge (79 N°)

    NASA Astrophysics Data System (ADS)

    Åström, Emmelie K. L.; Carroll, Michael L.; Sen, Arunima; Ambrose, William G., Jr.; Silyakova, Anna; Carroll, JoLynn

    2016-04-01

    Cold seeps are locations where hydrocarbons, sulfide or reduced compounds emanate from the seafloor, which may fuel chemoautotrophic production and form additional hard bottom substrate through carbonate precipitation. Chemosynthetic symbiosis, trophic interactions, and additional bottom substrate types can provide a heterogeneous environment for deep-sea organisms supporting macrofaunal communities including increased biodiversity and biomass. We combined quantitative benthic faunal samples with sea floor photographs from an active, methane seeping pockmark at Vestnesa Ridge (1200 meters depth) to examine community structure and biodiversity in a high Arctic deep cold seep. Quantitative data were compared with samples from the nearby inactive Svyatogor Ridge (1577-1706 meters depth). We measured highly elevated methane concentrations (up to 100x background levels) in the sediment at Vestnesa Ridge. Faunal abundance, species richness and biomass were significantly higher at the Vestnesa pockmark compared to inactive Svyatogor Ridge. Seabed photos from Vestnesa Ridge reveal high megafaunal diversity and biomass and cold seep features including carbonate crust and microbial mats. Our observations indicate that chemoautotrophic production enhances deep-sea biomass and diversity at Vestnesa Ridge. The focused methane emissions create a heterogeneous deep-sea habitat for chemo-associated organisms coexisting with heterotrophic conventional fauna in a high Arctic seep. Keywords: Arctic, benthic ecology, biodiversity, chemosynthesis, methane

  2. Mexico.

    PubMed

    1993-01-01

    The background notes on Mexico provide text and recent statistical information on the geography, population, government, economy, and foreign relations, specifically the North American Free Trade Agreement with US. The 1992 population is estimated at 89 million of which 60% are mestizo (Indian-Spanish), 30% are American Indian, 9% are Caucasian, and 1% are other. 90% are Roman Catholic. There are 8 years of compulsory education. Infant mortality is 30/1000 live births. Life expectancy for males is 68 years and 76 years for females. The labor force is comprised of 30% in services, 24% in agriculture and fishing, 19% in manufacturing, 13% in commerce, 7% in construction, 4% in transportation and communication, and .4% in mining. There are 31 states and a federal district. Gross domestic product (GDP) per capita was $3200 in 1991. Military expenditures were .5% of GDP in 1991. The average inflation rate is 19%. Mexico City with 20 million is the largest urban center in the world. In recent years, the economy has been restructured with market oriented reforms; the result has been a growth of GDP of 3.6% in 1991 from 2% in 1987. Dependence on oil exports has decreased. There has been privatization and deregulation of state-owned companies. Subsidies to inefficient companies have been stopped. Tariff rates were reduced. The financial debt has been reduced and turned into a surplus of .8% in 1992. Mexico's foreign debt has been reduced from its high in 1987 of $107 billion. Agricultural reforms have been ongoing for 50 years. Land was redistributed, but standards of living and productivity have improved only slightly. Rural land tenure regulations have been changed, and other economic reforms are expected. Mexico engages in ad hoc international groups and is selective about membership in international organizations. PMID:12178052

  3. Mollusks from late Mesozoic seep deposits, chiefly in California.

    PubMed

    Kaim, Andrzej; Jenkins, Robert G; Tanabe, Kazushige; Kiel, Steffen

    2014-01-01

    Twenty-nine mollusk species from Late Jurassic to Eocene hydrocarbon seep deposits from California (USA), Japan, New Zealand, and Barbados are described and illustrated. Twenty species belong to Gastropoda and nine to Bivalvia. Seven new species, three new genera, and one new family are introduced. The gastropod Hikidea gen. nov. includes smooth-shelled Cantrainea-like colloniins from Cretaceous hydrocarbon seeps and plesiosaur falls. Hikidea osoensis sp. nov. is the oldest species of this genus. Chilodonta? reticulata sp. nov. is a distinctive vetigastropod though its supraspecific position is unclear. Phanerolepida onoensis sp. nov. is the first species of this colloniin genus from a seep deposit. We describe two new genera of Hokkaidoconchidae: Abyssomelania gen. nov. and Ascheria gen. nov.; this family includes now four genera (including Hokkaidoconcha and Humptulipsia) and ranges from the Late Jurassic to the Eocene. Abyssomelania is characterized by a large, high-spired shell and unusual widely-spaced prosocline riblets (here called abyssomelaniid riblets). Abyssomelania is represented by two new species: A. cramptoni sp. nov. from the Late Cretaceous of New Zealand and A. campbellae sp. nov. from the Early Cretaceous of California. Ascheria gen. nov. is characterized by a large high-spired cerithiform shell, a subsutural constriction, and mostly reticulate ornament. Two nominate species are included: Ascheria gigantea (Kiel et al., 2008) and A. eucosmeta (Ascher, 1906), both of Early Cretaceous age. Two further species potentially belonging to Ascheria from the Eocene of Barbados are reported in open nomenclature and are re-illustrated and re-described for comparison. Humtulipsia nobuharai sp. nov. is described based on specimens from the Campanian-Maastrichtian Sada Limestone seep deposit in Japan. The new family Paskentanidae fam. nov. is introduced for the genera Paskentana and Atresius. The species of this family are characterized by thin-shelled, broad

  4. Biogeography and Potential Exchanges Among the Atlantic Equatorial Belt Cold-Seep Faunas

    PubMed Central

    Olu, Karine; Cordes, Erik E.; Fisher, Charles R.; Brooks, James M.; Sibuet, Myriam; Desbruyères, Daniel

    2010-01-01

    Like hydrothermal vents along oceanic ridges, cold seeps are patchy and isolated ecosystems along continental margins, extending from bathyal to abyssal depths. The Atlantic Equatorial Belt (AEB), from the Gulf of Mexico to the Gulf of Guinea, was one focus of the Census of Marine Life ChEss (Chemosynthetic Ecosystems) program to study biogeography of seep and vent fauna. We present a review and analysis of collections from five seep regions along the AEB: the Gulf of Mexico where extensive faunal sampling has been conducted from 400 to 3300m, the Barbados accretionary prism, the Blake ridge diapir, and in the Eastern Atlantic from the Congo and Gabon margins and the recently explored Nigeria margin. Of the 72 taxa identified at the species level, a total of 9 species or species complexes are identified as amphi-Atlantic. Similarity analyses based on both Bray Curtis and Hellinger distances among 9 faunal collections, and principal component analysis based on presence/absence of megafauna species at these sites, suggest that within the AEB seep megafauna community structure is influenced primarily by depth rather than by geographic distance. Depth segregation is observed between 1000 and 2000m, with the middle slope sites either grouped with those deeper than 2000m or with the shallower sites. The highest level of community similarity was found between the seeps of the Florida escarpment and Congo margin. In the western Atlantic, the highest degree of similarity is observed between the shallowest sites of the Barbados prism and of the Louisiana slope. The high number of amphi-atlantic cold-seep species that do not cluster according to biogeographic regions, and the importance of depth in structuring AEB cold-seep communities are the major conclusions of this study. The hydrothermal vent sites along the Mid Atlantic Ridge (MAR) did not appear as “stepping stones” for dispersal of the AEB seep fauna, however, the south MAR and off axis regions should be further

  5. Using a video-corer to evaluate hydrocarbon fluxes in the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Hung, C. C.; Wang, C. C.; Chen, H. H.; Lin, Y. S.; Huang, K. H.

    2015-12-01

    Many natural methane seeps exist in the northern South China Sea. Researchers have often used gravity corers or piston corers to collect sediments and bottom seawater for estimating methane fluxes of these seeps. The actual sampling locations of these corers are difficult to match seeping vents detected by scientific echo sounder because of the difficulty in positioning of these corers when sampling at sea,. Thus, the hydrocarbon fluxes of the seeping vents estimated using these corers might not be representative hydrocarbon fluxes of seeping vents in the northern South China Sea. In this study, we used a real-time video multicorer to collect surface sediments and bottom seawater samples. This real-time multicorer can accurately obtain surface sediments and bottom seawater samples on hydrocarbon seeping vents. To estimate hydrocarbon diffusion fluxes of seeps in the northern South China Sea, we analyzed methane concentrations and carbon isotopes of methane in both porewater and bottom seawater. During the cruises conducted from August to December, 2014, methane fluxes in the study area ranged from 3 to 57000 μmol m-2 d-1 which are significantly higher than previously reported values (~160 μmol m-2 d-1). Besides, we have obtained some samples in the study area using real-time multicorer in 2015. These new results will be presented in the meeting. Overall, the observed result in this study suggests that the in-situ multicorer can be a suitable instrument sampling surface sediments and bottom seawater samples on hydrocarbon seeping vents.

  6. Morphology of Florida Escarpment chemosynthetic brine seep community sites

    SciTech Connect

    Paull, C.K.; Spiess, F.N.; Curray, J.R.; Twitchell, D.

    1988-01-01

    The Florida Escarpment near 26/sup 0/N was surveyed with Deep-Two, Seabeam, and GLORIA in the area where chemosynthetic communities were discovered via ALVIN in the abyssal Gulf of Mexico. Seabeam bathymetry and GLORIA images indicate that the escarpment is a generally straight cliff with average slopes of about 45/sup 0/ from 2,200 to more than 3,250 m. The escarpment's face is cut by 2-km wide box canyons whose head walls are as steep as the intervening escarpment's face. The shapes of these canyons are difficult to explain with the traditional models of canyon formation. Sidescan sonar images and bottom photographs reveal that the escarpment's face is composed of a series of long, straight bedding-plane terraces which are truncated along nearly vertical orthogonal joints. Exposure of these truncated strata indicate the face of the escarpment is eroded. The contact between the basal escarpment and the flat-lying abyssal hemipelagic sediments is abrupt. Apparently, chemosynthetic communities line extensive sections of the escarpment base where reduced brines seep out into the sea floor. The morphology suggests joints and deep seeps are controlling factors in scarp retreat.

  7. Biogeochemical processes and microbial diversity of the Gullfaks and Tommeliten methane seeps (Northern North Sea)

    NASA Astrophysics Data System (ADS)

    Wegener, G.; Shovitri, M.; Knittel, K.; Niemann, H.; Hovland, M.; Boetius, A.

    2008-02-01

    Fluid-flow related seafloor structures and gas seeps were detected in the North Sea in the 1970s and 1980s by acoustic sub-bottom profiling and oil rig surveys. A variety of features like pockmarks, gas vents and authigenic carbonate cements were found to be associated with sites of oil and gas exploration, indicating a link between these surface structures and underlying deep hydrocarbon reservoirs. In this study we performed acoustic surveys and videographic observation at Gullfaks, Holene Trench, Tommeliten, Witch's Hole and the giant pockmarks of the UK Block 15/25, to investigate the occurrence and distribution of cold seep ecosystems in the Northern North Sea. The most active gas seep sites, i.e. Gullfaks and Tommeliten, were investigated in detail: at both sites gas bubbles escaped continuously from small holes in the seabed to the water column, reaching the upper mixed surface layer as indicated by acoustic images of the gas flares. At Gullfaks a 0.1 km2 large gas emission site was detected on a flat sandy seabed, covered by filamentous sulfide-oxidizing bacteria. At Tommeliten we found a patchy distribution of small bacterial mats indicating sites of gas seepage. Here the seafloor consists of layers of sand and stiff clay, and gas emission was observed from small cracks in the seafloor. At both sites the anaerobic oxidation of methane (AOM) coupled to sulfate reduction is the major source of sulfide. Molecular analyses targeting specific lipid biomarkers and 16 S rRNA gene sequences identified an active microbial community dominated by sulfide-oxidizing and sulfate-reducing bacteria (SRB) as well as methanotrophic bacteria and archaea. Carbon isotope values of specific microbial fatty acids and alcohols were highly depleted, indicating that the microbial community at both gas seeps incorporates methane or its metabolites. The microbial community composition of both shallow seeps show high similarities to the deep water seeps associated with gas hydrates

  8. Radium decay series dating of barite deposition in the Gulf of Mexico: Initial results

    SciTech Connect

    Van Gent, D.L.; Scott, L.M.; Fu, B.

    1995-12-31

    Barite deposits consisting of chimneys and crusts were recently documented and recovered by submersible from hydrocarbon seeps in the Gulf of Mexico offshore Louisiana at water depths of 510-670 m in the Garden Banks and Mississippi Canyon areas. This is the first discovery of barite deposits associated with cold hydrocarbon seeps. The outer part of the chimneys are dominated by barite whereas the inner part of the chimneys are dominated by barite with pyrite as accessory mineral. The crusts are about 5-8 cm thick and their surficial layers are composed of barite coexisting with carbonate whereas the lower part of the crusts consists of barite, carbonate, and pyrite. A program of radiometric dating by Ra decay series isotopes was initiated in order to derive a chronology of barite deposition in association with the hydrocarbon seeps. Chimneys and crusts were analyzed for NORM using a high purity intrinsic germanium gamma spectroscopy system. The deposits were found to contain {sup 226}Ra and {sup 228}Ra at concentrations comparable to those found in scale associated with oil production in the Gulf States Region (approximately 500 pCi/gm and 250 pCi/gm, respectively). The deposits were subjected to two separate age dating techniques. The primary technique utilized gamma spectroscopy for determination of {sup 210}Pb/{sup 226}Ra ratios. The second technique utilized gamma spectroscopy for determination of {sup 226}Th/{sup 228}Ra ratios. Ages as determined by {sup 210}Pb/{sup 226}Ra ranged from 2 years to 40 years. The {sup 228}Th/{sup 228}Ra methodology tended to validate the primary dating technique, although the useful range of dating for this method does not exceed 15 years. Sulfide-rich layers in the barite deposits tended to give anomalous and biased results when dated by the primary method. Both methodologies also appear valid for age dating scale deposits {le} 100 years old that are generated in oil production operations.

  9. Questa baseline and pre-mining ground-water quality investigation. 20. Water chemistry of the Red River and selected seeps, tributaries, and precipitation, Taos County, New Mexico, 2000-2004

    USGS Publications Warehouse

    Verplanck, P.L.; McCleskey, R.B.; Nordstrom, D.K.

    2006-01-01

    As part of a multi-year project to infer the pre-mining ground-water quality at Molycorp's Questa mine site, surface-water samples of the Red River, some of its tributaries, seeps, and snow samples were collected for analysis of inorganic solutes and of water and sulfate stable isotopes in selected samples. The primary aim of this study was to document diel, storm event, and seasonal variations in water chemistry for the Red River and similar variations in water chemistry for Straight Creek, a natural analog site similar in topography, hydrology, and geology to the mine site for inferring pre-mining water-quality conditions. Red River water samples collected between 2000 and 2004 show that the largest variations in water chemistry occur during late summer rainstorms, often monsoonal in nature. Within hours, discharge of the Red River increased from 8 to 102 cubic feet per second and pH decreased from 7.80 to 4.83. The highest concentrations of metals (iron, aluminum, zinc, manganese) and sulfate also occur during such events. Low-pH and high-solute concentrations during rainstorm runoff are derived primarily from alteration 'scar' areas of naturally high mineralization combined with steep topography that exposes continually altered rock because erosion is too rapid for vegetative growth. The year 2002 was one of the driest on record, and Red River discharge reflected the low seasonal snow pack. No snowmelt peak appeared in the hydrograph record, and a late summer storm produced the highest flow for the year. Snowmelt was closer to normal during 2003 and demonstrated the dilution effect of snowmelt on water chemistry. Two diel sampling events were conducted for the Red River, one during low flow and the other during high flow, at two locations, at the Red River gaging station and just upstream from Molycorp's mill site. No discernible diel trends were observed except for dissolved zinc and manganese at the upstream site during low flow. Straight Creek drainage water

  10. Association Between Ambient Levels of Polycyclic Aromatic Hydrocarbons and Small for Gestational Age Hispanic Infants Born Along the United States-Mexico Border.

    PubMed

    Maypole-Keenan, Coty M; Symanski, Elaine; Stock, Thomas H; Waller, D Kim

    2016-02-01

    Few studies have examined associations between polycyclic aromatic hydrocarbons (PAHs) and birth outcomes, and no studies have been conducted in El Paso County Texas, along the United States-Mexico border. Infants born from 2005-2007 to Hispanic mothers with a birth weight less than the 10th percentile for gestational age and sex were classified as small for gestational age (SGA). PAH exposures were estimated for the entire period of gestation and for each trimester of pregnancy using ambient air monitoring data from 2004-2007. Logistic regression was used to estimate odds ratios for the association between PAH levels and SGA infants. There was marked seasonal variation in the carcinogenic PAHs. Established risk factors for SGA were observed to be associated with SGA births in this population. No associations were detected between PAH levels and SGA births. These findings provide no evidence of an association between PAHs and SGA infants. PMID:24585213

  11. The carbon isotope biogeochemistry of the individual hydrocarbons in bat guano and the ecology of the insectivorous bats in the region of Carlsbad, New Mexico

    NASA Technical Reports Server (NTRS)

    Des Marais, D. J.; Mitchell, J. M.; Meinschein, W. G.; Hayes, J. M.

    1980-01-01

    The structures and C-13 contents of individual hydrocarbons extracted from bat guano found in the Carlsbad region of New Mexico are analyzed in order to elucidate details of the carbon flow in the plant-insect-bat ecosystem. Carbon isotopic analyses indicate that equivalent numbers of plants with C3 and C4 photosynthetic pathways occupy the feeding area of the bats, which supports alfalfa and cotton as well as native plants. The molecular composition of the guano is consistent with an origin in two distinct populations of insects with different feeding habits, one of which may graze predominantly on crops. It is also pointed out that isotopic analyses of more ancient guano deposits may be useful in characterizing prevalent vegetation and climate of earlier periods.

  12. Aryl hydrocarbon receptor-mediated activity of particulate organic matter from the Paso del Norte airshed along the U.S.-Mexico border.

    PubMed Central

    Arrieta, Daniel E; Ontiveros, Cynthia C; Li, Wen-Whai; Garcia, Jose H; Denison, Michael S; McDonald, Jacob D; Burchiel, Scott W; Washburn, Barbara Shayne

    2003-01-01

    In this study, we determined the biologic activity of dichloromethane-extracted particulate matter < 10 micro m in aerodynamic diameter (PM10) obtained from filters at three sites in the Paso del Norte airshed, which includes El Paso, Texas, USA; Juarez, Chihuahua, Mexico, and Sunland Park, New Mexico, USA. The extracts were rich in polycyclic aromatic hydrocarbons (PAHs) and had significant biologic activity, measured using two in vitro assay systems: ethoxyresorufin-(O-deethylase (EROD) induction and the aryl hydrocarbon-receptor luciferase reporter system. In most cases, both EROD (5.25 pmol/min/mg protein) and luciferase activities (994 relative light units/mg) were highest in extracts from the Advance site located in an industrial neighborhood in Juarez. These values represented 58% and 55%, respectively, of induction associated with 1 micro M ss-naphthoflavone exposures. In contrast, little activity was observed at the Northeast Clinic site in El Paso, the reference site. In most cases, luciferase and EROD activity from extracts collected from the Tillman Health Center site, situated in downtown El Paso, fell between those observed at the other two sites. Overall, a statistically significant correlation existed between PM10 and EROD and luciferase activities. Chemical analysis of extracts collected from the Advance site demonstrated that concentrations of most PAHs were higher than those reported in most other metropolitan areas in the United States. Calculations made with these data suggest a cancer risk of 5-12 cases per 100,000 people. This risk estimate, as well as comparisons with the work of other investigators, raises concern regarding the potential for adverse health effects to the residents of this airshed. Further work is needed to understand the sources, exposure, and effects of PM10 and particulate organic material in the Paso del Norte airshed. PMID:12896850

  13. Anaerobic methane oxidation in low-organic content methane seep sediments

    USGS Publications Warehouse

    Pohlman, John W.; Riedel, Michael; Bauer, James E.; Canuel, Elizabeth A.; Paull, Charles K.; Lapham, Laura; Grabowski, Kenneth S.; Coffin, Richard B.; Spence, George D.

    2013-01-01

    Sulfate-dependent anaerobic oxidation of methane (AOM) is the key sedimentary microbial process limiting methane emissions from marine sediments and methane seeps. In this study, we investigate how the presence of low-organic content sediment influences the capacity and efficiency of AOM at Bullseye vent, a gas hydrate-bearing cold seep offshore of Vancouver Island, Canada. The upper 8 m of sediment contains 14C. A fossil origin for the DIC precludes remineralization of non-fossil OM present within the sulfate zone as a significant contributor to pore water DIC, suggesting that nearly all sulfate is available for anaerobic oxidation of fossil seep methane. Methane flux from the SMT to the sediment water interface in a diffusion-dominated flux region of Bullseye vent was, on average, 96% less than at an OM-rich seep in the Gulf of Mexico with a similar methane flux regime. Evidence for enhanced methane oxidation capacity within OM-poor sediments has implications for assessing how climate-sensitive reservoirs of sedimentary methane (e.g., gas hydrate) will respond to ocean warming, particularly along glacially-influenced mid and high latitude continental margins.

  14. Microbial Oxidation of Ethane within Seep Sediment at Coal Oil Point, Santa Barbara, CA

    NASA Astrophysics Data System (ADS)

    Mendes, S. D.; Duncombe, R.; Scarlett, R. D.; Shaffer, J.; Lensch, S.; Valentine, D. L.

    2013-12-01

    The hydrocarbon seep field at Coal Oil Point (COP), off the coast of Santa Barbara, California, releases more than 10^10 g of thermogenic natural gas each year. Only a fraction of this methane, ethane, propane, and butane reaches the atmosphere, and is instead consumed by marine microbes in both the sediment and water column. Bacterial respiration of these gases has been observed in aerobic and anaerobic conditions, with the exception of ethane (aerobic only) (Kniemeyer et. al 2007). This work seeks to quantify the rate of ethane oxidation (both aerobic and anaerobic) in marine sediment. A series of experiments, to be conducted using COP seep sediment aboard the R/V Atlantis in October 2013, will test how varying oxygen conditions impact ethane oxidation rate. Oxidation rates will be quantified using sensitive 3H-ethane tracers. Preliminary data from Shane's Seep, located within the COP seep field, indicates that ethane oxidation is restricted to the top 6 cm of sediment. This suggests that oxygen is a limiting factor, but further work is needed to establish if ethane oxidation is restricted to exclusively aerobic environments.

  15. The carbon isotope biogeochemistry of the individual hydrocarbons in bat guano and the ecology of the insectivorous bats in the region of Carlsbad, New Mexico

    NASA Astrophysics Data System (ADS)

    Des Marais, David J.; Mitchell, J. M.; Meinschein, W. G.; Hayes, J. M.

    1980-12-01

    The structures and 13C contents of individual alkanes extracted from bat guano found in the Carlsbad region of New Mexico can be related to both the photosynthetic pathways of the local plants and the feeding habits of the insects that support the bats. Carbon isotopic analyses show that equivalent numbers of C 3 and C 4 native plant species occupy the Pecos River Valley, a very significant feeding area for the Carlsbad bats. During the seasons when bats frequent the area, the agricultural crops consist principally of alfalfa and cotton, both C 3 plants. The molecular composition of the bat guano hydrocarbons is fully consistent with an insect origin. Two isotopically distinct groups of insect branched alkanes were discerned. These two groups of alkanes derived from two chemotaxonomically distinct populations of insects possessing distinctly different feeding habits. It is possible that one population grazes predominantly on crops whereas the other population prefers native vegetation. This and other isotopic evidence suggests that crop pests constitute a major percentage of the bats' diet. Because the guano sample was less than 40 years old, this material reflects the present day plant community in the Pecos River Valley. Future studies of more ancient guano deposits should reveal a measurable influence of both natural and man-induced vegetative changes with time upon the 13C content of the bat guano hydrocarbons.

  16. Sulfur redox reactions: Hydrocarbons, native sulfur, Mississippi Valley-type deposits, and sulfuric acid karst in the Delaware Basin, New Mexico and Texas

    SciTech Connect

    Hill, C.A.

    1995-02-01

    Hydrocarbons, native sulfur, Mississippi Valley-type (MVT) deposits, and sulfuric acid karst in the Delaware Basin, southeastern New Mexico, and west Texas, USA, are all genetically related through a series of sulfur redox reactions. The relationship began with hydrocarbons in the basin that reacted with sulfate ions from evaporite rock to produce isotopically light ({delta}{sup 34}S = -22 to -12) H{sub 2}S and bioepigenetic limestone (castiles). This light H{sub 2}S was then oxidized at the redox interface to produce economic native sulfur deposits ({delta}{sup 34}S = -15 to +9) in the castiles, paleokarst, and along graben-boundary faults. This isotopically light H{sub 2}S also migrated from the basin into its margins to accumulate in structural (anticlinal) and stratigraphic (Yates siltstone) traps, where it formed MVT deposits within the zone of reduction ({delta}{sup 34}S = -15 to +7). Later in time, in the zone of oxidation, this H{sub 2}S reacted with oxygenated water to produce sulfuric acid, which dissolved the caves (e.g., Carlsbad Cavern and Lechuguilla Cave, Guadalupe Mountains). Massive gypsum blocks on the floors of the caves ({delta}{sup 34}S = -25 to +4) were formed as a result of this reaction. The H{sub 2}S also produced isotopically light cave sulfur ({delta}{sup 34}S = -24 to -15), which is now slowly oxidizing to gypsum in the presence of vadose drip water. 16 refs., 10 figs.

  17. Dispersants as Used in Response to the MC252-Spill Lead to Higher Mobility of Polycyclic Aromatic Hydrocarbons in Oil-Contaminated Gulf of Mexico Sand

    PubMed Central

    Zuijdgeest, Alissa; Huettel, Markus

    2012-01-01

    After the explosion of the Deepwater Horizon oil rig, large volumes of crude oil were washed onto and embedded in the sandy beaches and sublittoral sands of the Northern Gulf of Mexico. Some of this oil was mechanically or chemically dispersed before reaching the shore. With a set of laboratory-column experiments we show that the addition of chemical dispersants (Corexit 9500A) increases the mobility of polycyclic aromatic hydrocarbons (PAHs) in saturated permeable sediments by up to two orders of magnitude. Distribution and concentrations of PAHs, measured in the solid phase and effluent water of the columns using GC/MS, revealed that the mobility of the PAHs depended on their hydrophobicity and was species specific also in the presence of dispersant. Deepest penetration was observed for acenaphthylene and phenanthrene. Flushing of the columns with seawater after percolation of the oiled water resulted in enhanced movement by remobilization of retained PAHs. An in-situ benthic chamber experiment demonstrated that aromatic hydrocarbons are transported into permeable sublittoral sediment, emphasizing the relevance of our laboratory column experiments in natural settings. We conclude that the addition of dispersants permits crude oil components to penetrate faster and deeper into permeable saturated sands, where anaerobic conditions may slow degradation of these compounds, thus extending the persistence of potentially harmful PAHs in the marine environment. Application of dispersants in nearshore oil spills should take into account enhanced penetration depths into saturated sands as this may entail potential threats to the groundwater. PMID:23209777

  18. Dynamic fluid flow and chemical fluxes associated with a seafloor gas hydrate deposit on the northern Gulf of Mexico slope

    NASA Astrophysics Data System (ADS)

    Solomon, Evan A.; Kastner, Miriam; Jannasch, Hans; Robertson, Gretchen; Weinstein, Yishai

    2008-06-01

    Gas hydrates outcrop on the seafloor at the Bush Hill hydrocarbon seep site in the northern Gulf of Mexico. Four newly designed fluid flux meters/chemical samplers, called the MOSQUITO, were deployed for 430 days at Bush Hill to determine how dynamic subsurface fluid flow influences gas hydrate stability and to quantify the associated methane fluxes into the ocean. Three of the flux meters were deployed adjacent to an outcropping gas hydrate mound, while the fourth monitored background conditions. The flux meter measurements reveal that the subsurface hydrology in the vicinity of the mound is complex and variable with frequent changes from downward to upward flow ranging from - 161 to 273 cm/yr, and with temporal variations in the horizontal component of flow. The continuous record of fluid chemistry indicates that gas hydrate actively formed in the sediments. We propose that long periods of downward flow of seawater adjacent to gas vents (up to 4 months) are driven by local sub-pressure resulting from gas ebullition through faults and fractures due to overpressure at depth. High frequency variations in flow rates (days to weeks) are likely due to temporal changes in sediment permeability and the 3-D fluid flow field as a result of active gas hydrate and authigenic carbonate precipitation, as well as the presence of free gas. Gas hydrate formation occurred as a result of long-term emanation of CH4 at focused gas vents followed by a more diffuse intergranular methane flux. The estimated CH4 flux to the water column from focused gas vents across the Bush Hill seep is ~ 5•106 mol/yr. This significant flux suggests that Bush Hill and similar hydrocarbon seeps in the northwestern Gulf of Mexico may be important natural sources of methane to the ocean and possibly the atmosphere.

  19. Investigation of population structure in Gulf of Mexico Seepiophila jonesi (Polychaeta, Siboglinidae) using cross-amplified microsatellite loci

    PubMed Central

    Huang, Chunya; Schaeffer, Stephen W.; Fisher, Charles R.

    2016-01-01

    Background Vestimentiferan tubeworms are some of the most recognizable fauna found at deep-sea cold seeps, isolated environments where hydrocarbon rich fluids fuel biological communities. Several studies have investigated tubeworm population structure; however, much is still unknown about larval dispersal patterns at Gulf of Mexico (GoM) seeps. As such, researchers have applied microsatellite markers as a measure for documenting the transport of vestimentiferan individuals. In the present study, we investigate the utility of microsatellites to be cross-amplified within the escarpiid clade of seep vestimentiferans, by determining if loci originally developed for Escarpia spp. could be amplified in the GoM seep tubeworm, Seepiophila jonesi. Additionally, we determine if cross-amplified loci can reliably uncover the same signatures of high gene flow seen in a previous investigation of S. jonesi. Methods Seventy-seven S. jonesi individuals were collected from eight seep sites across the upper Louisiana slope (<1,000 m) in the GoM. Forty-eight microsatellite loci that were originally developed for Escarpia laminata (18 loci) and Escarpia southwardae (30 loci) were tested to determine if they were homologous and polymorphic in S. jonesi. Loci found to be both polymorphic and of high quality were used to test for significant population structuring in S. jonesi. Results Microsatellite pre-screening identified 13 (27%) of the Escarpia loci were homologous and polymorphic in S. jonesi, revealing that microsatellites can be amplified within the escarpiid clade of vestimentiferans. Our findings uncovered low levels of heterozygosity and a lack of genetic differentiation amongst S. jonesi from various sites and regions, in line with previous investigations that employed species-specific polymorphic loci on S. jonesi individuals retrieved from both the same and different seep sites. The lack of genetic structure identified from these populations supports the presence of

  20. Spatial distribution of diverse cold seep communities living on various diapiric structures of the southern Barbados prism

    NASA Astrophysics Data System (ADS)

    Olu, K.; Sibuet, M.; Harmegnies, F.; Foucher, J.-P.; Fiala-Médioni, A.

    , both associated with sulfur-oxydizing bacteria, and there were numerous empty shells. The densities and biomasses of symbiotic bivalves were far greater in the area studied than in a deeper mud volcano field on the same prism that had been studied previously. This is consistent with a report that methane production is greater in the southern region of this accretionary prism than in the northern. Numerous non-symbiotic organisms were observed in and around the areas of the seeps, some are endemic to the seep communities, including some gastropods and shrimps, others are either colonists or vagrants from the surrounding deep-sea floor. Filter feeders were very abundant, and some of these, like the serpulids and large sponges, may also be dependent on the chemosynthetic production. Faunistic composition of both symbiotic and non-symbiotic taxa, of the assemblages around these cold seeps, is closely related to that reported for communities living on hydrocarbon seeps in the Gulf of Mexico.

  1. Interactions between nitrogen cycling and methane oxidation in the pelagic waters of the Gulf of Mexico.

    NASA Astrophysics Data System (ADS)

    Joye, S. B.; Weber, S.; Battles, J.; Montoya, J. P.

    2014-12-01

    Methane is an important greenhouse gas that plays a critical role in climate variation. Although a variety of marine methane sources and sinks have been identified, key aspects of the fate of methane in the ocean remain poorly constrained. At cold seeps in the Gulf of Mexico and elsewhere, methane is introduced into the overlying water column via fluid escape from the seabed. We quantified the fate of methane in the water column overlying seafloor cold seeps, in a brine basin, and at several control sites. Our goals were to determine the factors that regulated methane consumption and assimilation and to explore how these controlling factors varied among and between sites. In particular, we examined the impact of nitrogen availability on methane oxidation and studied the ability of methane oxidizing bacteria to fix molecular nitrogen. Methane oxidation rates were highest in the methane rich bottom waters of natural hydrocabron seeps. At these sites, inorganic nitrogen addition stimulated methane oxidation in laboratory experiments. In vitro shipboard experiments revealed that rates of methane oxidation and nitrogen fixation were correlated strongly, suggesting that nitrogen fixation may have been mediated by methanotrophic bacteria. The highest rates of methane oxidation and nitrogen fixation were observed in the deepwater above at natural hydrocarbon seeps. Rates of methane oxidation were substantial along the chemocline of a brine basin but in these ammonium-rich brines, addition of inorganic nitrogen had little impact on methane oxidation suggesting that methanotrophy in these waters were not nitrogen limited. Control sites exhibited the lowest methane concentrations and methane oxidation rates but even these waters exhibited substantial potential for methane oxidation when methane and inorganic nitrogen concentrations were increased. Together, these data suggest that the availability of inorganic nitrogen plays a critical role in regulating methane oxidation in

  2. The effect of sulfide and an increased food supply on the meiofauna and macrofauna at the East Flower Garden brine seep

    NASA Astrophysics Data System (ADS)

    Powell, E. N.; Bright, T. J.; Brooks, J. M.

    1986-03-01

    A sulfurous brine seep at the East Flower Garden Bank, northwest Gulf of Mexico, produces conditions conducive to the growth of a luxuriant prokaryotic biota. Hydrodynamic cropping continually harvests this biota and distributes it to sandy-bottom and hard-bank benthic communities downstream of the seep. Consequently, both macro- and meiofaunal abundances are dramatically increased above the regional norm in parts of the seep system. When sulfide is present, the lower Bilaterian groups belonging to the meiofauna dominate the community; without sulfide, macrofaunal groups, particularly crustaceans, dominate the community. Outside the influence of the seep, meiofaunal copepods predominate. Changes in taxonomic composition and abundance indicate that the sandy-bottom benthos at 70 80 m depth at the East Flower Garden bank is foodlimited and that, under these conditions, meiofauna, particularly the higher Bilaterian groups, dominate the community numerically. Perhaps, under food-limiting conditions, meiofauna compete favorably with macrofauna for food.

  3. Environmental effects of submarine seeping natural gas

    NASA Astrophysics Data System (ADS)

    Dando, P. R.; Hovland, M.

    1992-10-01

    It is suspected that most shallow reservoirs of natural gas vent to the surface to some degree. This seeping may be through diffusion of dissolved gas or by a flow of gas bubbles which entrain interstitial water during the rise through the sediments to the surface. Methane bubbles dissolved other gases, notably hydrogen sulphide and carbon dioxide, during their ascent. Under suitable temperature-pressure conditions gas hydrates may be formed close to or at the seabed Black suphide-rich sediments and mats of sulphur oxidizing bacteria are frequently observed close to the sediments surface at seep sites, including a sharp oxic/anoxic boundary. Animal species associated with these gas seeps include both species which obtain nutrition from symbiotic methane-oxidizing bacteria and species with symbolic sulphur-oxidizing bacteria. It is suspected that at some microseepage an enhanced biomass of meiofauna and macrofauna is supported by a food chain based on free-living and symbiotic sulphur-oxidizing and methane-oxidizing bacteria. The most common seep-related features of sea floor topography are local depressions including pockmark craters. Winnowing of the sediment during their creation leads to an accumulation of larger detritis in the depressions. Where the deprssions overlies salt diapirs they may be filled with hypersaline solutions. In some areas dome-shaped features are associated with seepage and these may be colonized by coral reefs. Other reefs, "hard-grounds", columnar and disc-shaped protrusions, all formed of carbonate-cemented sediments, are common on the sea floor in seep areas. Much of the carbonate appears to be derived from carbon dioxide formed as a result of methane oxidation. The resulting hard-bottoms on the sea floor are often colonized by species not found on the neighboring soft-bottoms. As a result seep areas may be characterized by the presence of a rich epifauna.

  4. Cold Seep Epifaunal Communities on the Hikurangi Margin, New Zealand: Composition, Succession, and Vulnerability to Human Activities

    PubMed Central

    Bowden, David A.; Rowden, Ashley A.; Thurber, Andrew R.; Baco, Amy R.; Levin, Lisa A.; Smith, Craig R.

    2013-01-01

    Cold seep communities with distinctive chemoautotrophic fauna occur where hydrocarbon-rich fluids escape from the seabed. We describe community composition, population densities, spatial extent, and within-region variability of epifaunal communities at methane-rich cold seep sites on the Hikurangi Margin, New Zealand. Using data from towed camera transects, we match observations to information about the probable life-history characteristics of the principal fauna to develop a hypothetical succession sequence for the Hikurangi seep communities, from the onset of fluid flux to senescence. New Zealand seep communities exhibit taxa characteristic of seeps in other regions, including predominance of large siboglinid tubeworms, vesicomyid clams, and bathymodiolin mussels. Some aspects appear to be novel; however, particularly the association of dense populations of ampharetid polychaetes with high-sulphide, high-methane flux, soft-sediment microhabitats. The common occurrence of these ampharetids suggests they play a role in conditioning sulphide-rich sediments at the sediment-water interface, thus facilitating settlement of clam and tubeworm taxa which dominate space during later successional stages. The seep sites are subject to disturbance from bottom trawling at present and potentially from gas hydrate extraction in future. The likely life-history characteristics of the dominant megafauna suggest that while ampharetids, clams, and mussels exploit ephemeral resources through rapid growth and reproduction, lamellibrachid tubeworm populations may persist potentially for centuries. The potential consequences of gas hydrate extraction cannot be fully assessed until extraction methods and target localities are defined but any long-term modification of fluid flow to seep sites would have consequences for all chemoautotrophic fauna. PMID:24204691

  5. Mineralization of vestimentiferan tubes at methane seeps on the Congo deep-sea fan

    NASA Astrophysics Data System (ADS)

    Haas, Antonie; Little, Crispin T. S.; Sahling, Heiko; Bohrmann, Gerhard; Himmler, Tobias; Peckmann, Jörn

    2009-02-01

    Vestimentiferan tube worms are prominent members of modern methane seep communities and are totally reliant as adults on symbiotic sulphide-oxidizing bacteria for their nutrition. The sulphide is produced in the sediment by a biochemical reaction called the anaerobic oxidation of methane (AOM). A well-studied species from the Gulf of Mexico shows that seep vestimentiferans 'mine' sulphide from the sediment using root-like, thin walled, permeable posterior tube extensions, which can also be used to pump sulphate and possibly hydrogen ions from the soft tissue back into the sediment to increase the local rate of AOM. The 'root-balls' of exhumed seep vestimentiferans are intimately associated with carbonate nodules, which are a result of AOM. We have studied vestimentiferan specimens and associated carbonates from seeps at the Kouilou pockmark field on the Congo deep-sea fan and find that some of the posterior 'root' tubes of living specimens are enclosed with carbonate indurated sediment and other, empty examples are partially or completely replaced by the carbonate mineral aragonite. This replacement occurs from the outside of the tube wall inwards and leaves fine-scale relict textures of the original organic tube wall. The process of mineralization is unknown, but is likely a result of post-mortem microbial decay of the tube wall proteins by microorganisms or the precipitation from locally high flux of AOM derived carbonate ions. The aragonite-replaced tubes from the Kouilou pockmarks show similar features to carbonate tubes in ancient seep deposits and make it more likely that many of these fossil tubes are those of vestimentiferans. These observations have implications for the supposed origination of this group, based on molecular divergence estimates.

  6. Biogeochemical processes and microbial diversity of the Gullfaks and Tommeliten methane seeps (Northern North Sea)

    NASA Astrophysics Data System (ADS)

    Wegener, G.; Shovitri, M.; Knittel, K.; Niemann, H.; Hovland, M.; Boetius, A.

    2008-08-01

    Fluid flow related seafloor structures and gas seeps were detected in the North Sea in the 1970s and 1980s by acoustic sub-bottom profiling and oil rig surveys. A variety of features like pockmarks, gas vents and authigenic carbonate cements were found to be associated with sites of oil and gas exploration, indicating a link between these surface structures and the underlying, deep hydrocarbon reservoirs. In this study we performed acoustic surveys and videographic observation at Gullfaks, Holene Trench, Tommeliten, Witch's Hole and the giant pockmarks of the UK Block 15/25, to investigate the occurrence and distribution of cold seep ecosystems in the Northern North Sea. The most active gas seep sites, i.e. Gullfaks and Tommeliten, were investigated in detail. At both sites, gas bubbles escaped continuously from small holes in the seabed to the water column, reaching the upper mixed surface layer. At Gullfaks a gas emitting, flat area of 0.1 km2 of sandy seabed covered by filamentous sulfur-oxidizing bacteria was detected. At Tommeliten, we found a patchy distribution of small bacterial mats indicating sites of gas seepage. Below the patches the seafloor consisted of sand from which gas emissions were observed. At both sites, the anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SR) was the major source of sulfide. Molecular analyses targeting specific lipid biomarkers and 16S rRNA gene sequences identified an active microbial community dominated by sulfur-oxidizing and sulfate-reducing bacteria (SRB) as well as methanotrophic bacteria and archaea. Stable carbon isotope values of specific, microbial fatty acids and alcohols from both sites were highly depleted in the heavy isotope 13C, indicating that the microbial community incorporates methane or its metabolites. The microbial community composition of both shallow seeps shows high similarities to the deep water seeps associated with gas hydrates such as Hydrate Ridge or the Eel River basin.

  7. Biogenic methane from abyssal brine seeps at the base of the Florida escarpment

    SciTech Connect

    Martens, C.S.; Chanton, J.P.; Paull, C.K. )

    1991-08-01

    Dissolved methane is present at concentrations exceeding 10mM in the pore waters of sulfidic, salt-brine-enriched sediments underlying chemosynthetic communities at the base of the Florida escarpment. Light hydrocarbon samples were obtained from brine seep sediments by means of an in situ probe and push cores deployed by the deep submersible Alvin. Pore-water methane had a {delta}{sup 13}C value of {minus}83.3 {plus minus}7.0 (Peedee belemnite, N = 17), contained < 1.3% modern carbon, and was enriched over ethane concentrations by 10{sup 3} to 10{sup 5}; these results all indicate a fossil, biogenic carbon source within the Florida platform. Methane-rich brine fluids arriving at seep sites are depleted in dissolved sulfate, although they have been diluted twenty-fold with sulfate-rich seawater during transit. It appears that sulfate reduction and methano-genesis are important processes within the platform.

  8. Field Exploration of Methane Seep Near Atqasuk

    SciTech Connect

    Katey Walter, Dennis Witmer, Gwen Holdmann

    2008-12-31

    Methane (CH{sub 4}) in natural gas is a major energy source in the U.S., and is used extensively on Alaska's North Slope, including the oilfields in Prudhoe Bay, the community of Barrow, and the National Petroleum Reserve, Alaska (NPRA). Smaller villages, however, are dependent on imported diesel fuel for both power and heating, resulting in some of the highest energy costs in the U.S. and crippling local economies. Numerous CH{sub 4} gas seeps have been observed on wetlands near Atqasuk, Alaska (in the NPRA), and initial measurements have indicated flow rates of 3,000-5,000 ft{sup 3} day{sup -1} (60-100 kg CH{sub 4} day{sup -1}). Gas samples collected in 1996 indicated biogenic origin, although more recent sampling indicated a mixture of biogenic and thermogenic gas. In this study, we (1) quantified the amount of CH{sub 4} generated by several seeps and evaluated their potential use as an unconventional gas source for the village of Atqasuk; (2) collected gas and analyzed its composition from multiple seeps several miles apart to see if the source is the same, or if gas is being generated locally from isolated biogenic sources; and (3) assessed the potential magnitude of natural CH{sub 4} gas seeps for future use in climate change modeling.

  9. Methane-derived carbonates form at the sediment-bedrock interface in a shallow marine gas seep.

    NASA Astrophysics Data System (ADS)

    Kimball, J.; Ding, H.; Valentine, D. L.

    2006-12-01

    Hydrocarbon seeps occur world-wide, and release large quantities of oil and natural gas to the ocean and atmosphere. One of the world's most prolific hydrocarbon seep fields is located just offshore from Goleta, CA, and serves as the study site for this investigation. In the course of investigating gas fluxes from a 10 m deep coastal seep, samples of seafloor bedrock were collected by scuba diving during a time of low sediment burden. These samples were found to be concretions composed primarily of carbonate-cemented sand. The delta13C values of the carbonate range from -25 to -32 per mille, and indicate a role for methane oxidation in the formation of the carbonates. Long chain fatty acids were extracted from the concretions and were quantified, identified, and analyzed for their 13C composition. Fatty acids typical of sulfate reducing bacteria were observed, and interpreted as a signature of anoxia. Further mineralogical and isotopic studies are planned. From these observations we interpret a shallow water origin for these concretions, whereby the seasonal migration of sand to the seep environment drives anoxia and anaerobic methane oxidation at the sediment-bedrock interface. The alkalinity generated from sulfate reduction causes the precipitation of methane-derived carbonate- which forms a concretion with sand.

  10. Post depositional alteration of foraminiferal shells in cold seep settings: New insights from Flow-Through Time-Resolved Analyses of biogenic and inorganic seep carbonates

    NASA Astrophysics Data System (ADS)

    Martin, R.; Torres, M. E.; Klinkhammer, G. P.; Nesbitt, E. A.

    2010-12-01

    Transient hydrocarbon migration within a sediment package leaves behind robust geological signatures in the biogenic and authigenic carbonate record. Here we apply Flow-Through Time Resolved Analyses (FT-TRA) to unravel the compositional changes in foraminifera from coastal fossil methane seeps exposed from Oregon to Vancouver Island: The Eocene-Oligocene Keasey Formation, the Oligocene-Miocene Pysht and Sooke Formations, and the Pliocene Quinault Formation. Our data show that secondary mineralization can be traced with the use of Mg/Ca ratios, which in altered foraminifera are significantly higher than the biogenic ratio (<3 mmol/mol in biogenic carbonate compared to values as high as 69 mmol/mol for inorganic carbonate). Analogous to the record in authigenic carbonate, secondary mineralization contains valuable information about seep characteristics and their geologic history. Data from the Quinault Formation reflect the influence of anaerobic oxidation of biogenic methane in both bleb (δ13C: -29.8 ‰ to -14.0‰) and foraminiferal (δ13C: -43.0‰ to 2.0‰) carbonate. Oxygen isotopes from blebs and foraminifera indicate precipitation at bottom water temperatures in an environment comparable to conditions observed in modern seeps on the Oregon slope and elsewhere. The carbonates in these seeps are enriched in barium and strontium over biogenic values, and such elevated values may be used a diagnostic tool to identify methane-related carbonates. In contrast, in the Pysht and Sooke formations, carbonate precipitation (including secondary mineralization of foraminifera), was fueled by a thermogenic carbon source (δ13C: -14 to 3.4‰). These carbonates reflect a more complex paragenetic history and suggest alteration driven by post-depositional warm and/or meteoric fluids.

  11. Sulfuric acid speleogenesis of Carlsbad Cavern and its relationship to hydrocarbons, Delaware basin, New Mexico and Texas

    SciTech Connect

    Hill, C.A. )

    1990-11-01

    Sulfur-isotope data and pH-dependence of the mineral endellite support the hypothesis that Carlsbad Cavern and other caves in the Guadalupe Mountains were dissolved primarily by sulfuric acid rather than by carbonic acid. Floor gypsum deposits up to 10 m thick and native sulfur in the caves are significantly enriched in {sup 32}S; {delta}{sup 34}S values as low as {minus}25.8 {per thousand} (CDT) indicate that the cave sulfur and gypsum are the end products of microbial reactions associated with hydrocarbons. A model for a genetic connection between hydrocarbons in the basin and caves in the Guadalupe Mountains is proposed. As the Guadalupe Mountains were uplifted during the late Pliocene-Pleistocene, oil and gas moved updip in the basin. The gas reacted with sulfate anions derived from dissolution of the Castile anhydrite to form H{sub 2}S, CO{sub 2}, and castile limestone. The hydrogen sulfide rose into the Capitan reef along joints, forereef carbonate beds, or Bell Canyon siliciclastic beds and there reacted with oxygenated groundwater to form sulfuric acid and Carlsbad Cavern. A sulfuric-acid mode of dissolution may be responsible for large-scale porosity of some Delaware basin reservoirs and for oil-field karst reservoirs in other petroleum basins of the world. 8 figs.

  12. Distribution and concentrations of petroleum hydrocarbons associated with the BP/Deepwater Horizon Oil Spill, Gulf of Mexico.

    PubMed

    Sammarco, Paul W; Kolian, Steve R; Warby, Richard A F; Bouldin, Jennifer L; Subra, Wilma A; Porter, Scott A

    2013-08-15

    We examined the geographic extent of petroleum hydrocarbon contamination in sediment, seawater, biota, and seafood during/after the BP/Deepwater Horizon Oil Spill (April 20-July 15, 2010; 28.736667°N, -88.386944°W). TPH, PAHs, and 12 compound classes were examined, particularly C1-benzo(a)anthracenes/chrysenes, C-2-/C-4-phenanthrenes/anthracenes, and C3-naphthalenes. Sediment TPH, PAHs, and all classes peaked near Pensacola, Florida, and Galveston, Texas. Seawater TPH peaked off Pensacola; all of the above classes peaked off the Mississippi River, Louisiana and Galveston. Biota TPH and PAHs peaked near the Mississippi River; C-3 napthalenes peaked near the spill site. Seafood TPH peaked near the spill site, with PAHs and all classes peaking near Pensacola. We recommend that oil concentrations continued to be monitored in these media well after the spill has ceased to assist in defining re-opening dates for fisheries; closures should be maintained until hydrocarbon levels are deemed within appropriate limits. PMID:23831318

  13. Induction of c-Jun by air particulate matter (PM₁₀) of Mexico city: Participation of polycyclic aromatic hydrocarbons.

    PubMed

    Salcido-Neyoy, Martha Estela; Sánchez-Pérez, Yesennia; Osornio-Vargas, Alvaro Román; Gonsebatt, María Eugenia; Meléndez-Zajgla, Jorge; Morales-Bárcenas, Rocío; Petrosyan, Pavel; Molina-Servin, Edith Danny; Vega, Elizabeth; Manzano-León, Natalia; García-Cuellar, Claudia M

    2015-08-01

    The carcinogenic potential of urban particulate matter (PM) has been partly attributed to polycyclic aromatic hydrocarbons (PAHs) content, which activates the aryl hydrocarbon receptor (AhR). Here we report the effect of PM with an aerodynamic size of 10 μm (PM10) on the induction of AhR pathway in A549 cells, evaluating its downstream targets CYP1B1, IL-6, IL-8 and c-Jun. Significant increases in CYP1B1 protein and enzyme activity; IL-6 and IL-8 secretion and c-Jun protein were found in response to PM10. The formation of PAH-DNA adducts was also detected. The involvement of AhR pathway was confirmed with Resveratrol as AhR antagonist, which reversed CYP1B1 and c-Jun induction. Nevertheless, in IL-6 and IL-8 secretion, the Resveratrol was ineffective, suggesting an effect independent of this pathway. Considering the role of c-Jun in oncogenesis, its induction by PM may be contributing to its carcinogenic potential through induction of AhR pathway by PAHs present in PM10. PMID:25909326

  14. Concentrations in human blood of petroleum hydrocarbons associated with the BP/Deepwater Horizon oil spill, Gulf of Mexico.

    PubMed

    Sammarco, Paul W; Kolian, Stephan R; Warby, Richard A F; Bouldin, Jennifer L; Subra, Wilma A; Porter, Scott A

    2016-04-01

    During/after the BP/Deepwater Horizon oil spill, cleanup workers, fisherpersons, SCUBA divers, and coastal residents were exposed to crude oil and dispersants. These people experienced acute physiological and behavioral symptoms and consulted a physician. They were diagnosed with petroleum hydrocarbon poisoning and had blood analyses analyzed for volatile organic compounds; samples were drawn 5-19 months after the spill had been capped. We examined the petroleum hydrocarbon concentrations in the blood. The aromatic compounds m,p-xylene, toluene, ethylbenzene, benzene, o-xylene, and styrene, and the alkanes hexane, 3-methylpentane, 2-methylpentane, and iso-octane were detected. Concentrations of the first four aromatics were not significantly different from US National Health and Nutritional Examination Survey/US National Institute of Standards and Technology 95th percentiles, indicating high concentrations of contaminants. The other two aromatics and the alkanes yielded equivocal results or significantly low concentrations. The data suggest that single-ring aromatic compounds are more persistent in the blood than alkanes and may be responsible for the observed symptoms. People should avoid exposure to crude oil through avoidance of the affected region, or utilizing hazardous materials suits if involved in cleanup, or wearing hazardous waste operations and emergency response suits if SCUBA diving. Concentrations of alkanes and PAHs in the blood of coastal residents and workers should be monitored through time well after the spill has been controlled. PMID:25998020

  15. Application of Satellite SAR for Discovery and Quantification of Natural Marine Oil Seeps

    NASA Astrophysics Data System (ADS)

    Amos, J.; Lai, R.; Zimmer, B.; Leiva, A.; MacDonald, I.

    2006-12-01

    Natural marine oil seeps discharge gassy drops from the seafloor. Oil drops and gas bubbles reach the surface from water depths as great as 3000m. The oil spreads rapidly, forming an invisible layer that drifts down-wind and down-current in long, linear streaks called slicks. Oil slicks are visible in SAR data because the surfactant dampens capillary waves and reduces backscatter. Application of SAR as an exploration tool in energy prospecting is well-established. We have applied this technique for discovering the chemosynthetic communities that colonize the seafloor in the vicinity of deep-water seeps on the continental margin of the Gulf of Mexico. The management goal for this effort is to prevent harmful impact to these communities resulting from exploration or production activities. The scientific goals are to delineate the zoogeography of the chemosynthetic fauna, which is widespread on continental margins, and to establish study sites where their life history can be investigated. In the course of an ongoing, multidisciplinary study in the spring and summer of 2006, we explored 20 possible sites where SAR and geophysical data indicated seeps might occur. SAR was only partly diagnostic: all sites with SAR-detected slicks were found to have biologic communities, but communities were also found at geophysical anomalies that did not produce slicks. We acquired over 60 RADARSAT SAR images from the northern Gulf of Mexico in cooperation with the Alaska Satellite Facility. The ship RV ATLANTIS was at sea during the acquisition and collected synoptic weather and oceanographic data. To automate interpretation of large image dataset we have employed texture recognition with use of a library of textons applied iteratively to the images. This treatment shows promise in distinguishing floating oil from false targets generated by rain fronts and other phenomena. One goal of the analysis is to delineate bounding boxes to quantify the ocean area covered by the thin oil layer

  16. Fates, Budgets, and Health Implications of Macondo Spill Volatile Hydrocarbons in the Ocean and Atmosphere of the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Leifer, I.; Barletta, B.; Blake, D. R.; Blake, N. J.; Bradley, E. S.; Meinardi, S.; Lehr, B.; Luyendyk, B. P.; Roberts, D. A.; Rowland, F. S.

    2010-12-01

    The Macondo Oil Spill released unprecedented oil and gas to the ocean, estimated at 63000 bbl/day, which dispersed and dissolved during rise (Technical Flow Rate Team Report, 2010); yet, most of the oil reached the sea surface as oil slicks that then evolved due to weathering and dispersant application (Mass Balance Report, 2010). Remote sensing (near infrared imaging spectrometry) allowed quantification of thick surface oil, values of which were incorporated into an overall oil budget calculation. Remote sensing data, atmospheric samples, and numerical modeling, strongly suggest significant volatile loss during rise, yet measured atmospheric concentrations were high. Scaling atmospheric measurements to the total oil spill implies very high, extensive, and persistent levels of atmospheric petroleum hydrocarbon exposure with strong health implications to on-site workers and to coastal residents from wind advection.

  17. The carbon isotope biogeochemistry of the individual hydrocarbons in bat guano and the ecology of insectivorous bats in the region of Carlsbad, New Mexico

    NASA Technical Reports Server (NTRS)

    Desmarais, D. J.; Mitchell, J. M.; Meinschein, W. G.; Hayes, J. M.

    1980-01-01

    The structures and C-13 contents of individual alkanes extracted from bat guano found in the Carlsbad region of New Mexico can be related to both the photosynthetic pathways of the local plants and the feeding habits of the insects that support the bats. Carbon isotopic analyses of the 62 most important plant species in the Pecos River Valley, the most significant feeding area for the Carlsbad bats, reveal the presence of 29 species with C3 photosynthesis and 33 species, mostly grasses, with C4 photosynthesis. Although the abundances of nonagricultural C3 and C4 plants are similar, alfalfa and cotton, both C3 plants, constitute over 95 per cent of the crop biomass. The molecular composition of the bat guano hydrocarbons is fully consistent with an insect origin. Two isotopically distinct groups of insect branched alkanes were discerned. These two groups of alkanes derived from two chemotaxonomically distinct populations of insects possessing distinctly different feeding habits. It is likely that one population grazes predominantly on crops whereas the other population prefers native vegetation. This and other isotopic evidence supports the notion that crop pests constitute a major percentage of the bats' diet.

  18. Natural and unnatural oil slicks in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    MacDonald, I. R.; Garcia-Pineda, O.; Beet, A.; Daneshgar Asl, S.; Feng, L.; Graettinger, G.; French-McCay, D.; Holmes, J.; Hu, C.; Huffer, F.; Leifer, I.; Muller-Karger, F.; Solow, A.; Silva, M.; Swayze, G.

    2015-12-01

    When wind speeds are 2-10 m s-1, reflective contrasts in the ocean surface make oil slicks visible to synthetic aperture radar (SAR) under all sky conditions. Neural network analysis of satellite SAR images quantified the magnitude and distribution of surface oil in the Gulf of Mexico from persistent, natural seeps and from the Deepwater Horizon (DWH) discharge. This analysis identified 914 natural oil seep zones across the entire Gulf of Mexico in pre-2010 data. Their ˜0.1 µm slicks covered an aggregated average of 775 km2. Assuming an average volume of 77.5 m3 over an 8-24 h lifespan per oil slick, the floating oil indicates a surface flux of 2.5-9.4 × 104 m3 yr-1. Oil from natural slicks was regionally concentrated: 68%, 25%, 7%, and <1% of the total was observed in the NW, SW, NE, and SE Gulf, respectively. This reflects differences in basin history and hydrocarbon generation. SAR images from 2010 showed that the 87 day DWH discharge produced a surface-oil footprint fundamentally different from background seepage, with an average ocean area of 11,200 km2 (SD 5028) and a volume of 22,600 m3 (SD 5411). Peak magnitudes of oil were detected during equivalent, ˜14 day intervals around 23 May and 18 June, when wind speeds remained <5 m s-1. Over this interval, aggregated volume of floating oil decreased by 21%; area covered increased by 49% (p < 0.1), potentially altering its ecological impact. The most likely causes were increased applications of dispersant and surface burning operations.

  19. Natural and unnatural oil slicks in the Gulf of Mexico

    USGS Publications Warehouse

    Ian R. MacDonald; O. Garcia-Pineda; A. Beet; S. Daneshgar Asl; L. Feng; D. G. Graettinger; D. French-McCay; J. Holmes; C. Hu; F. Huffer; I. Leifer; F. Mueller-Karger; A. Solow; M. Silva; Swayze, Gregg A.

    2015-01-01

    When wind speeds are 2 – 10 m s−1, reflective contrasts in the ocean surface make oil slicks visible to synthetic aperture radar (SAR) under all sky conditions. Neural network analysis of satellite SAR images quantified the magnitude and distribution of surface oil in the Gulf of Mexico from persistent, natural seeps and from the Deepwater Horizon (DWH) discharge. This analysis identified 914 natural oil seep zones across the entire Gulf of Mexico in pre-2010 data. Their ∼0.1 µm slicks covered an aggregated average of 775 km2. Assuming an average volume of 77.5 m3over an 8 – 24 h lifespan per oil slick, the floating oil indicates a surface flux of 2.5 – 9.4 × 104 m3 y−1. Oil from natural slicks was regionally concentrated: 68%, 25%, 7%, and <1% of the total was observed in the NW, SW, NE and SE Gulf, respectively. This reflects differences in basin history and hydrocarbon generation. SAR images from 2010 showed that the 87-day DWH discharge produced a surface-oil footprint fundamentally different from background seepage, with an average ocean area of 11,200 km2 (SD 5,028) and a volume of 22,600 m3 (SD 5,411). Peak magnitudes of oil were detected during equivalent, ∼14-day intervals around 23 May and 18 June, when wind speeds remained <5 m s−1. Over this interval, aggregated volume of floating oil decreased by 21%; area covered increased by 49% (p < .1), potentially altering its ecological impact. The most likely causes were increased applications of dispersant and surface burning operations.

  20. Brine induced low-Magnesium calcite formation at cold seeps

    NASA Astrophysics Data System (ADS)

    Feng, Dong; Roberts, Harry; Joye, Samantha; Heydari, Ezat

    2013-04-01

    Low-Mg calcite (LMC; < 5 mol% Mg), commonly observed during time intervals of "calcite seas," since the beginning of the Paleozoic Era, is a good indicator of low Mg/Ca ratio (< 2) in seawater. Calcite seas were coincident with times of active seawater-basalt interactions along mid-ocean ridges at high temperatures, which extract Mg from seawater and release Ca to it. In the modern aragonite sea, most carbonate minerals precipitate at the seafloor, including deposits from cold seep environments are primarily either aragonite or high-Mg calcite (HMC). Here, we report the finding of non-skeletal LMC from cold seeps in Alaminos Canyon block 601 (AC 601), 2200 m below the sea surface on northern Gulf of Mexico (GOM) continental slope. Low-Mg calcite usually represents the only carbonate mineral in the studied samples. Dominant allochems in these seep carbonates are peloids, grain aggregates, pelagic forams, and fragments of mollusks and echinoids. The limestone is heavily cemented. The observed cements include micrite, microspar, mosaic, bladed, fan, and needle cements. The dissolution of grains and cements was observed. Not only originally aragonitic mollusks shells, but also carbonate cement have been dissolved. The aerobic oxidation of reduced chemical species such as methane and H2S is responsible for an increase in pCO2 and a decrease of pH, leading to local carbonate dissolution. The occurrence of oxic conditions is confirmed by the presence of negative Ce anomalies of the carbonates. Further, we report on analyses showing that the ambient porewater Mg/Ca ratio actually governs the carbonate mineralogy. The occurrence of LMC may be attributed to the brine fluids, which is relatively Mg-depleted (Mg/Ca mole ratio is below 0.7) compared to pore fluid of the subsurface sediments from the reference site (Mg/Ca mole ratio is above 4.1) that usually produce HMC. The 87Sr/86Sr values of LMC (mean = 0.708001, sd = 0.000034, n=2) are significantly lower than that of the

  1. Feeder pipes - Expression of the uppermost plumbing system in Oligocene methane-seep deposits, Washington State, USA

    NASA Astrophysics Data System (ADS)

    Zwicker, Jennifer; Smrzka, Daniel; Gier, Susanne; Goedert, James; Peckmann, Jörn

    2015-04-01

    Plumbing systems of methane seeps are complex pathways along which hydrocarbon-rich fluids migrate upward through the marine sedimentary column. Seeps commonly maintain fluid flow over long periods of time, providing a steady supply of methane to shallow sediments and the water column. At greater sediment depths, fluid transport is facilitated by faults and conduits, which enable migration of fluids sourced from deep hydrocarbon reservoirs. In the shallow subsurface, plumbing systems may become successively filled by authigenic carbonates, whose precipitation is partly triggered by sulfate-dependent anaerobic oxidation of methane (AOM). To expand our knowledge on the uppermost plumbing network of ancient seeps, this work investigates fluid conduits that were mineralized by a distinct succession of authigenic mineral phases. These mineralized conduits, which occur below an Oligocene seep deposit from the Lincoln Creek Formation in Washington State, are referred to as feeder pipes here. The concentrically-zoned feeder pipes are 2 to 3 cm in diameter. The mineral phase that formed first is matrix micrite, making up the outer part of pipes. Toward the center, pipes are filled by clear, banded and botryoidal aragonite cement, which is intercalated with yellow aragonite cement. The innermost portions of the pipes are filled by either pipe-filling micrite, microspar, or brownish calcite. The observed paragenetic sequences archive successions of various biogeochemical processes. Clear and yellow aragonite cements are distinctly depleted in 13C, revealing that their formation was favored by AOM. In contrast, later phases including brownish calcite and microspar are enriched in 13C, pointing to precipitation from fluids affected by methanogenesis. Their size and morphology indicate that the pipes were initially produced by seep-dwelling, burrowing organisms. The burrows subsequently acted as preferred fluid pathways. Possible producers of the burrows include various bivalves

  2. Metagenomic analysis of microbial consortium from natural crude oil that seeps into the marine ecosystem offshore Southern California

    SciTech Connect

    Hawley, Erik R.; Piao, Hailan; Scott, Nicole M.; Malfatti, Stephanie; Pagani, Ioanna; Huntemann, Marcel; Chen, Amy; del Rio, Tijana G.; Foster, Brian; Copeland, A.; Jansson, Janet K.; Pati, Amrita; Gilbert, Jack A.; Tringe, Susannah G.; Lorenson, Thomas D.; Hess, Matthias

    2014-01-02

    Crude oils can be major contaminants of the marine ecosystem and microorganisms play a significant role in the degradation of the main constituents of crude oil. To increase our understanding of the microbial hydrocarbon degradation process in the marine ecosystem, we collected crude oil from an active seep area located in the Santa Barbara Channel (SBC) and generated a total of about 52 Gb of raw metagenomic sequence data. The assembled data comprised ~500 Mb, representing ~1.1 million genes derived primarily from chemolithoautotrophic bacteria. Members of Oceanospirillales, a bacterial order belonging to the Deltaproteobacteria, recruited less than 2% of the assembled genes within the SBC metagenome. In contrast, the microbial community associated with the oil plume that developed in the aftermath of the Deepwater Horizon (DWH) blowout in 2010, was dominated by Oceanospirillales, which comprised more than 60% of the metagenomic data generated from the DWH oil plume. This suggests that Oceanospirillales might play a less significant role in the microbially mediated hydrocarbon conversion within the SBC seep oil compared to the DWH plume oil. We hypothesize that this difference results from the SBC oil seep being mostly anaerobic, while the DWH oil plume is aerobic. Within the Archaea, the phylum Euryarchaeota, recruited more than 95% of the assembled archaeal sequences from the SBC oil seep metagenome, with more than 50% of the sequences assigned to members of the orders Methanomicrobiales and Methanosarcinales. These orders contain organisms capable of anaerobic methanogenesis and methane oxidation (AOM) and we hypothesize that these orders and their metabolic capabilities may be fundamental to the ecology of the SBC oil seep.

  3. Metagenomic analysis of microbial consortium from natural crude oil that seeps into the marine ecosystem offshore Southern California

    PubMed Central

    Hawley, Erik R.; Piao, Hailan; Scott, Nicole M.; Malfatti, Stephanie; Pagani, Ioanna; Huntemann, Marcel; Chen, Amy; Glavina del Rio, Tijana; Foster, Brian; Copeland, Alex; Jansson, Janet; Pati, Amrita; Tringe, Susannah; Gilbert, Jack A.; Lorenson, Thomas D.; Hess, Matthias

    2014-01-01

    Crude oils can be major contaminants of the marine ecosystem and microorganisms play a significant role in the degradation of its main constituents. To increase our understanding of the microbial hydrocarbon degradation process in the marine ecosystem, we collected crude oil from an active seep area located in the Santa Barbara Channel (SBC) and generated a total of about 52 Gb of raw metagenomic sequence data. The assembled data comprised ~500 Mb, representing ~1.1 million genes derived primarily from chemolithoautotrophic bacteria. Members of Oceanospirillales, a bacterial order belonging to the Deltaproteobacteria, recruited less than 2% of the assembled genes within the SBC metagenome. In contrast, the microbial community associated with the oil plume that developed in the aftermath of the Deepwater Horizon (DWH) blowout in 2010, was dominated by Oceanospirillales, which comprised more than 60% of the metagenomic data generated from the DWH oil plume. This suggests that Oceanospirillales might play a less significant role in the microbially mediated hydrocarbon conversion within the SBC seep oil compared to the DWH plume oil. We hypothesize that this difference results from the SBC oil seep being mostly anaerobic, while the DWH oil plume is aerobic. Within the Archaea, the phylum Euryarchaeota, recruited more than 95% of the assembled archaeal sequences from the SBC oil seep metagenome, with more than 50% of the sequences assigned to members of the orders Methanomicrobiales and Methanosarcinales. These orders contain organisms capable of anaerobic methanogenesis and methane oxidation (AOM) and we hypothesize that these orders – and their metabolic capabilities – may be fundamental to the ecology of the SBC oil seep. PMID:25197496

  4. High-throughput transcriptome sequencing of the cold seep mussel Bathymodiolus platifrons.

    PubMed

    Wong, Yue Him; Sun, Jin; He, Li Sheng; Chen, Lian Guo; Qiu, Jian-Wen; Qian, Pei-Yuan

    2015-01-01

    Bathymodiolid mussels dominate hydrothermal vents, cold methane/sulfide-hydrocarbon seeps, and other sites of organic enrichment. Here, we aimed to explore the innate immune system and detoxification mechanism of the deep sea mussel Bathymodiolus platifrons collected from a methane seep in the South China Sea. We sequenced the transcriptome of the mussels' gill, foot and mantle tissues and generated a transcriptomic database containing 96,683 transcript sequences. Based on GO and KEGG annotations, we reported transcripts that were related to the innate immune system, heavy metal detoxification and sulfide metabolic genes. Our in-depth analysis on the isoforms of peptidoglycan recognition protein (PGRP) that have different cellular location and potentially differential selectivity towards peptidoglycan (PGN) from gram-positive and gram-negative bacteria were differentially expressed in different tissues. We also reported a potentially novel form of metallothionein and the production of phytochelatin in B. platifrons, which has not been reported in any of its coastal relative Mytilus mussel species. Overall, the present study provided new insights into heavy metal and sulfide metabolism in B. platifrons and can be served as the basis for future molecular studies on host-symbiont interactions in cold seep mussels. PMID:26593439

  5. High-throughput transcriptome sequencing of the cold seep mussel Bathymodiolus platifrons

    PubMed Central

    Wong, Yue Him; Sun, Jin; He, Li Sheng; Chen, Lian Guo; Qiu, Jian-Wen; Qian, Pei-Yuan

    2015-01-01

    Bathymodiolid mussels dominate hydrothermal vents, cold methane/sulfide-hydrocarbon seeps, and other sites of organic enrichment. Here, we aimed to explore the innate immune system and detoxification mechanism of the deep sea mussel Bathymodiolus platifrons collected from a methane seep in the South China Sea. We sequenced the transcriptome of the mussels’ gill, foot and mantle tissues and generated a transcriptomic database containing 96,683 transcript sequences. Based on GO and KEGG annotations, we reported transcripts that were related to the innate immune system, heavy metal detoxification and sulfide metabolic genes. Our in-depth analysis on the isoforms of peptidoglycan recognition protein (PGRP) that have different cellular location and potentially differential selectivity towards peptidoglycan (PGN) from gram-positive and gram-negative bacteria were differentially expressed in different tissues. We also reported a potentially novel form of metallothionein and the production of phytochelatin in B. platifrons, which has not been reported in any of its coastal relative Mytilus mussel species. Overall, the present study provided new insights into heavy metal and sulfide metabolism in B. platifrons and can be served as the basis for future molecular studies on host-symbiont interactions in cold seep mussels. PMID:26593439

  6. Characterization of coal-derived hydrocarbons and source-rock potential of coal beds, San Juan Basin, New Mexico and Colorado, U.S.A.

    USGS Publications Warehouse

    Rice, D.D.; Clayton, J.L.; Pawlewicz, M.J.

    1989-01-01

    Coal beds are considered to be a major source of nonassociated gas in the Rocky Mountain basins of the United States. In the San Juan basin of northwestern New Mexico and southwestern Colorado, significant quantities of natural gas are being produced from coal beds of the Upper Cretaceous Fruitland Formation and from adjacent sandstone reservoirs. Analysis of gas samples from the various gas-producing intervals provided a means of determining their origin and of evaluating coal beds as source rocks. The rank of coal beds in the Fruitland Formation in the central part of the San Juan basin, where major gas production occurs, increases to the northeast and ranges from high-volatile B bituminous coal to medium-volatile bituminous coal (Rm values range from 0.70 to 1.45%). On the basis of chemical, isotopic and coal-rank data, the gases are interpreted to be thermogenic. Gases from the coal beds show little isotopic variation (??13C1 values range -43.6 to -40.5 ppt), are chemically dry (C1/C1-5 values are > 0.99), and contain significant amounts of CO2 (as much as 6%). These gases are interpreted to have resulted from devolatilization of the humic-type bituminous coal that is composed mainly of vitrinite. The primary products of this process are CH4, CO2 and H2O. The coal-generated, methane-rich gas is usually contained in the coal beds of the Fruitland Formation, and has not been expelled and has not migrated into the adjacent sandstone reservoirs. In addition, the coal-bed reservoirs produce a distinctive bicarbonate-type connate water and have higher reservoir pressures than adjacent sandstones. The combination of these factors indicates that coal beds are a closed reservoir system created by the gases, waters, and associated pressures in the micropore coal structure. In contrast, gases produced from overlying sandstones in the Fruitland Formation and underlying Pictured Cliffs Sandstone have a wider range of isotopic values (??13C1 values range from -43.5 to -38

  7. Significance of anoxic slope basins to occurrence of hydrocarbons along flexure trend, Gulf of Mexico: a reappraisal

    SciTech Connect

    Dinkelman, M.G.; Curry, D.J.

    1987-05-01

    Recently, Tertiary anoxic slope basins have been proposed as the sources for much of the oil occurring along the Flexure Trend in the Gulf of Mexico. The intraslope basins are thought to have been formed in response to salt diapirism and concomitant salt withdrawal resulting from differential sediment loading between the basins and the diapirs, as well as due to associated faulting. Of the modern intraslope basins, the black, organic-rich muds accumulating in the Orca basin have especially attracted and are suggested to be modern analogs to late Tertiary source rocks accumulated and buried across the continental slope. Although the organic carbon content of the anoxic sediments in the Orca basin is generally high (2 to 3%), the concentration of preserved oil-generative organic matter in these sediments is low. Rock-Eval P2 yields are usually in the range of 340 to 1620 ppm, and hydrogen indices are generally less than 100. Pyrolysis-GC and 13C-NMR data show that up to 30 + % of the organic carbon is contained in carboxyl and other oxygenated groups, which are lost during diagenesis and early catagenesis of the sediments, and that much of the remainder is aromatized and degraded. The degradation was probably by oxidation during settling through the oxic water column. The geochemical data indicate, therefore, that the bulk of the organic carbon in the Orca basin is not capable of forming oil during catagenesis. Published regional cross sections across the Texas-Louisiana continental margin commonly show a thick (0.5-4 km), continuous salt sequence, sourcing salt diapirs and ridges, to underlie the Oligocene(.)/Miocene to Pleistocene sedimentary section of the outer continental shelf and slope.

  8. Mutagenicity and polycyclic aromatic hydrocarbons associated with extractable organic matter from airborne particles ⩽10 μm in southwest Mexico City

    NASA Astrophysics Data System (ADS)

    Villalobos-Pietrini, Rafael; Amador-Muñoz, Omar; Waliszewski, Stefan; Hernández-Mena, Leonel; Munive-Colín, Zenaida; Gómez-Arroyo, Sandra; Bravo-Cabrera, José Luis; Frías-Villegas, Alejandro

    A year-long sampling and analysis of 24 h airborne particles equal to or less than 10 μm (PM 10) was conducted in Southwest (SW) Mexico City in 1998. The amount of airborne PM 10 and its extractable organic matter (EOM) were highly correlated. The year 1998 was particularly dry with many fires, and higher values of PM 10 and EOM were obtained in the fire period (February-May) compared to the without fire period (January, June-December). The indirect-acting mutagenicity ( Salmonella typhimurium strain TA98 with mammalian metabolic activation, S9) did not correlate with the monthly concentrations of PM 10 and EOM, while the direct-acting mutagenicity (strains TA98 and YG1021, without mammalian metabolic activation) did correlate. The highest monthly mutagenic potency of TA98+S9 and of TA98-S9 were registered in May which correspond to the fire period, while for YG1021 the highest was in December, a without fire month. The highest TA98+S9/TA98-S9 ratios appeared from April to September (with the exception of June), indicating that emission of the direct mutagens occurred in the rest of the year (the coldest months), and December showed the highest mutagenicity of YG1021. The correlation of this mutagenicity with the number of ground-based inversions indicated a greater emissions of nitroarenes in the coldest months emitted mainly by vehicular traffic as shown by the correlation between YG1021 with CO and with NO 2. We did not find a correlation in the EOM of the complex mixtures between TA98+S9 and the total concentration of polycyclic aromatic hydrocarbons (PAH) nor between TA98+S9 and specific PAH. The analysis by gas chromatography/mass spectrometry indicated the presence of retene, a PAH found in the fire period and considered a softwood burning marker. The concentrations of fluoranthene and benz[ a]anthracene correlated with that of retene and with the burned area; they were the only PAH that presented significant differences between the periods with fire and

  9. Natural and Unnatural Oil Layers on the Surface of the Gulf of Mexico Detected and Quantified in Synthetic Aperture RADAR Images with Texture Classifying Neural Network Algorithms

    NASA Astrophysics Data System (ADS)

    MacDonald, I. R.; Garcia-Pineda, O. G.; Morey, S. L.; Huffer, F.

    2011-12-01

    Effervescent hydrocarbons rise naturally from hydrocarbon seeps in the Gulf of Mexico and reach the ocean surface. This oil forms thin (~0.1 μm) layers that enhance specular reflectivity and have been widely used to quantify the abundance and distribution of natural seeps using synthetic aperture radar (SAR). An analogous process occurred at a vastly greater scale for oil and gas discharged from BP's Macondo well blowout. SAR data allow direct comparison of the areas of the ocean surface covered by oil from natural sources and the discharge. We used a texture classifying neural network algorithm to quantify the areas of naturally occurring oil-covered water in 176 SAR image collections from the Gulf of Mexico obtained between May 1997 and November 2007, prior to the blowout. Separately we also analyzed 36 SAR images collections obtained between 26 April and 30 July, 2010 while the discharged oil was visible in the Gulf of Mexico. For the naturally occurring oil, we removed pollution events and transient oceanographic effects by including only the reflectance anomalies that that recurred in the same locality over multiple images. We measured the area of oil layers in a grid of 10x10 km cells covering the entire Gulf of Mexico. Floating oil layers were observed in only a fraction of the total Gulf area amounting to 1.22x10^5 km^2. In a bootstrap sample of 2000 replications, the combined average area of these layers was 7.80x10^2 km^2 (sd 86.03). For a regional comparison, we divided the Gulf of Mexico into four quadrates along 90° W longitude, and 25° N latitude. The NE quadrate, where the BP discharge occurred, received on average 7.0% of the total natural seepage in the Gulf of Mexico (5.24 x10^2 km^2, sd 21.99); the NW quadrate received on average 68.0% of this total (5.30 x10^2 km^2, sd 69.67). The BP blowout occurred in the NE quadrate of the Gulf of Mexico; discharged oil that reached the surface drifted over a large area north of 25° N. Performing a

  10. Interannual Variability and Trends of C2-C11 Non-Methane Hydrocarbons in a Subtropical Area close to the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Rappenglück, Bernhard

    2016-04-01

    Speciated C2-C11 non-methane hydrocarbons (NMHC) have been measured online on an hourly basis at Lake Jackson/TX close to the Gulf of Mexico. Altogether 48 NMHCs, including the GAW NMHC compounds, along with NO, NO2, NOx, O3 have been collected continuously from January 2004-December 2013 under the auspices of the Texas Commission on Environmental Quality. Data was screened for background conditions representing marine wind sectors. The data set represents a combination of marine air masses mixed with local biogenic emissions. The data analysis addresses photochemical processing of air masses as reflected in the relationship of ln(n-butane/ethane) vs. ln(propane/ethane) and ln(i-butane/ethane) vs. ln(n-butane/ethane). In addition, key NMHC relationships for radical chemistry, e.g. i-butane vs n-butane for OH and Cl chemistry and i-pentane vs. n-pentane for NO3 chemistry, are discussed. Seasonal analysis revealed a clear trend with maximum NMHC mixing ratios in winter time and lowest mixing ratios in summer reflecting the impact of photochemical processes in summer. Propene equivalents were highest during summertime, with significant contributions from alkenes, including isoprene. The relation of propane/ethane vs ethane indicates seasonal variation with lowest values (i.e. most aged air masses) in winter. Contrary to usual GAW NMHC sampling procedures, which at least requires routine daytime samples (e.g. for canister samplings), continuous NMHC data collection allows to analyze nighttime data, which is least impacted by photochemical processes and potentially well-suited for trend analysis. Corresponding trend analysis for the Lake Jackson data suggests an overall slight decrease of selected NMHCs over the 2004-2013 period.

  11. Global dispersion and local diversification of the methane seep microbiome

    PubMed Central

    Ruff, S. Emil; Biddle, Jennifer F.; Teske, Andreas P.; Knittel, Katrin; Boetius, Antje

    2015-01-01

    Methane seeps are widespread seafloor ecosystems shaped by the emission of gas from seabed reservoirs. The microorganisms inhabiting methane seeps transform the chemical energy in methane to products that sustain rich benthic communities around the gas leaks. Despite the biogeochemical relevance of microbial methane removal at seeps, the global diversity and dispersion of seep microbiota remain unknown. Here we determined the microbial diversity and community structure of 23 globally distributed methane seeps and compared these to the microbial communities of 54 other seafloor ecosystems, including sulfate–methane transition zones, hydrothermal vents, coastal sediments, and deep-sea surface and subsurface sediments. We found that methane seep communities show moderate levels of microbial richness compared with other seafloor ecosystems and harbor distinct bacterial and archaeal taxa with cosmopolitan distribution and key biogeochemical functions. The high relative sequence abundance of ANME (anaerobic methanotrophic archaea), as well as aerobic Methylococcales, sulfate-reducing Desulfobacterales, and sulfide-oxidizing Thiotrichales, matches the most favorable microbial metabolisms at methane seeps in terms of substrate supply and distinguishes the seep microbiome from other seafloor microbiomes. The key functional taxa varied in relative sequence abundance between different seeps due to the environmental factors, sediment depth and seafloor temperature. The degree of endemism of the methane seep microbiome suggests a high local diversification in these heterogeneous but long-lived ecosystems. Our results indicate that the seep microbiome is structured according to metacommunity processes and that few cosmopolitan microbial taxa mediate the bulk of methane oxidation, with global relevance to methane emission in the ocean. PMID:25775520

  12. Cruise summary for P-1-02-SC: acoustic imaging of natural oil and gas seeps and measurement of dissolved methane concentration in coastal waters near Pt. Conception, California

    USGS Publications Warehouse

    Lorenson, T.D.; Dougherty, Jennifer A.; Ussler, William, III; Paull, Charles K.

    2003-01-01

    Water-column acoustic anomalies and methane concentrations were documented in coastal waters surrounding Pt. Conception, California, in March 2002. The purpose of this survey, supported by the Minerals Management Service, was to locate active oil and gas seeps in the area as a background for further studies to determine hydrocarbon flux, mainly oil, into the environment. Objectives in reaching this goal are to (1) document the locations and geochemically fingerprint natural seeps within the offshore southern Santa Maria Basin; (2) geochemically fingerprint coastal tar residues and potential sources, both onshore and offshore, in this region; (3) establish chemical correlations between offshore active seeps and coastal residues thus linking seep sources to oil residues; (4) measure the rate of natural seepage of individual seeps and attempt to assess regional natural oil and gas seepage rates; (5) attempt to predict transport pathways of oil from seep sources to the coastline and; (6) interpret the petroleum system history for the natural seeps. This survey, addressing objective 1, focused on the area from offshore Surf Beach to the north and Gaviota to the south in water depths ranging from 20 to 500m. In addition, nine stations were sampled outside this area to provide a regional context. Water-column methane concentrations were measured in water samples collected from the R/V Point Sur with Niskin bottles from various depths. A total of 724 water samples from 94 stations were collected.

  13. Insights into the activity, formation and origin of seep systems on the seafloor in the SW Barents Sea

    NASA Astrophysics Data System (ADS)

    Mangelsdorf, Kai; Nickel, Julia C.; di Primio, Rolando; Kallmeyer, Jens; Horsfield, Brian; Stoddart, Daniel; Brunstad, Harald

    2014-05-01

    The southwestern Loppa High region, being part of the Barents Sea located in the north of Norway, is a promising area for oil and gas exploration since hydrocarbon discoveries have been made in this area in recent time. Additionally, surface features for hydrocarbon seepage, so called "cold seeps" have been detected on the seafloor, comprising extensive pockmark fields, carbonate crusts bearing areas and fault related gas flares. Leaking hydrocarbons are of specific interest since they are potential indicators for hydrocarbon reservoirs in the subsurface and the emitting hydrocarbons such as the greenhouse gas methane can have significant impact on the evolution of global warming when reaching the atmosphere. In this study cold seep systems like huge pockmark areas and carbonate crust sites from the SW Loppa High region were examined in detail, in order to determine the activity, formation and spatial distribution of the different seepage structures as well as the origin and timing of the seeping hydrocarbon fluids. The sample material comprising sediment cores from pockmarks, reference sites and carbonate crust areas as well as carbonate crust samples have been analyzed applying a combined biogeochemical and microbiological approach. In the carbonate crust area diagnostic biomarkers for the anaerobic oxidation of methane (AOM) were detected in the sediments as well as in the corresponding carbonate crusts. Their depth profiles show a distinct interval of higher concentrations, which points towards a shallow AOM zone in the investigated core. The biomarkers were also characterized by very negative carbon isotope signatures, indicating the involvement of the source microorganisms in the process of AOM. These data and active gas bubbling during sampling indicate the presence of methane at the carbonate crust site. In contrast in the pockmark areas active release of gas from the sediment could not be observed, neither in the gas measurement nor in the biogeochemical

  14. Importance of Chemolithoautotrophic Production to Mobile Benthic Predators in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Morgan, E.; Macavoy, S.; Carney, R.

    2005-05-01

    The continental slope of the Gulf of Mexico is characterized by substantial hydrocarbon seepage which provides reduced energy sources, both CH4 and H2S, for chemolithoautotrophs existing as endosymbionts within mussels and tubeworms found in dense colonies that provide habitat for an array of endemic and colonial fauna. The extent of trophic export of chemosynthetic biomass to the seep communities and the surrounding benthic communities in the Gulf, however, remains an open question. To elucidate the nutritional associations between seep residents and the surrounding benthos the carbon, nitrogen and sulfur stable isotope values of the hagfish Eptatretus sp., the giant isopod Bathynomus giganteus and the predatory snail Phymorhyncus sp. were interpreted through a three source, dual isotope mixing model. The model was able to assess the contributions of different isotopic signals to a mixture and thus could distinguish between photosynthetic/phytodetritus based sources, methanotrophic sources and thiotrophic sources. Incorporation of chemosynthetic based food sources was minimal on the whole and species specific; however some of the organisms considered in this study did incorporate nutrition from chemolithoautotrophic sources.

  15. Abyssal seep site cementation: west Florida escarpment

    SciTech Connect

    Neumann, A.C.; Paull, C.K.; Commeau, R.; Commeau, J.; Chanton, J.; Martens, C.; Gardemal, M.; Trumbull, W.; Showers, W.

    1988-02-01

    The deepest submarine cements known so far occur along the 3300-m deep base of the Florida escarpment and are associated with methane-bearing brine seeps, which emanate there. These deep Holocene carbonates, which occur as surficial and buried crusts, burrow fillings, and friable horizons, were sampled via ALVIN. The carbonates form irregular halos extending up to 20 m from seeps colonized by chemosynthetic fauna. Mussels, gastropods, and clams, the carbonate components of the community, produce a shell hash that is locally cemented by coarsely crystalline low-Mg calcite. Halos of palisade calcite are reminiscent of ancient examples of marine cements. Also present are carbonate hemipelagics cemented by micrite into crusts and burrow fillings. The degree of cementation varies from pervasive to light. Slabs of cemented crust up to 30 cm thick contrast with typical shallow crusts and exhibit irregular tops and smooth bottoms indicating different chemical gradients and pathways. Bulk /delta//sup 13/C values of the carbonates are low, ranging from /minus/ 2.4 to /minus/ 48.5 /per thousand/ (PDB) and implicating as the carbonate source the biogenic methane that occurs in high concentrations at the seeps. The interaction of methane and sulfate in these cement reactions is still unclear. The presence of course mollusk-fragment hardgrounds overlying an eroded limestone and covered by hemipelagics, if encountered elsewhere, could be mistaken for a much shallower setting. The erosion of limestone scarps and the concurrent development of deep hardgrounds containing a fossil chemosynthetic fauna at the unconformity is a scenario that needs to be included in the growing list of limestone facies interpretations.

  16. Petroleum-influenced beach sediments of the Campeche Bank, Mexico: diversity and bacterial community structure assessment.

    PubMed

    Rosano-Hernández, María C; Ramírez-Saad, Hugo; Fernández-Linares, Luis

    2012-03-01

    The bacterial diversity and community structure were surveyed in intertidal petroleum-influenced sediments of ≈ 100 km of a beach, in the southern Gulf of Mexico. The beach was divided in twenty sampling sites according to high, moderate and low petroleum influence. Densities of cultured heterotrophic (HAB) and hydrocarbon degrading bacteria (HDB) were highly variable in sediments, with little morphological assortment in colonies. PCR-RISA banding patterns differentiated distinct communities along the beach, and the bacterial diversity changed inversely to the degree of petroleum hydrocarbon influence: the higher TPH concentration, the lower genotype diversity. Seven DNA sequences (Genbank EF191394 -EF191396 and EF191398 -EF191401) were affiliated to uncultured members of Gemmatimonas, Acidobacterium, Desulfobacteraceae, Rubrobacterales, Actinobacterium and the Fibrobacteres/Acidobacteria group; all the above taxa are known for having members with active roles in biogeochemical transformations. The remaining sequences (EF191388 - EF191393 and EF191397) affiliated to Pseudoalteromonas, and to oil-degrading genera such as Pseudomonas, Vibrio and Marinobacter, being the last one an obligate oil-degrading bacterium. An exchange of bacteria between the beach and the oil seep environment, and the potential cleaning-up role of bacteria at the southern Gulf of Mexico are discussed. PMID:21802196

  17. Hydrocarbon pneumonia

    MedlinePlus

    Pneumonia - hydrocarbon ... Coughing Fever Shortness of breath Smell of a hydrocarbon product on the breath Stupor (decreased level of ... Most children who drink or inhale hydrocarbon products and develop ... hydrocarbons may lead to rapid respiratory failure and death.

  18. Cenozoic Methane-Seep Faunas of the Caribbean Region.

    PubMed

    Kiel, Steffen; Hansen, Bent T

    2015-01-01

    We report new examples of Cenozoic cold-seep communities from Colombia, Cuba, the Dominican Republic, Trinidad, and Venezuela, and attempt to improve the stratigraphic dating of Cenozoic Caribbean seep communities using strontium isotope stratigraphy. Two seep faunas are distinguished in Barbados: the late Eocene mudstone-hosted 'Joes River fauna' consists mainly of large lucinid bivalves and tall abyssochrysoid gastropods, and the early Miocene carbonate-hosted 'Bath Cliffs fauna' containing the vesicomyid Pleurophopsis, the mytilid Bathymodiolus and small gastropods. Two new Oligocene seep communities from the Sinú River basin in Colombia consist of lucinid bivalves including Elongatolucina, thyasirid and solemyid bivalves, and Pleurophopsis. A new early Miocene seep community from Cuba includes Pleurophopsis and the large lucinid Meganodontia. Strontium isotope stratigraphy suggests an Eocene age for the Cuban Elmira asphalt mine seep community, making it the oldest in the Caribbean region. A new basal Pliocene seep fauna from the Dominican Republic is characterized by the large lucinid Anodontia (Pegophysema). In Trinidad we distinguish two types of seep faunas: the mudstone-hosted Godineau River fauna consisting mainly of lucinid bivalves, and the limestone-hosted Freeman's Bay fauna consisting chiefly of Pleurophopsis, Bathymodiolus, and small gastropods; they are all dated as late Miocene. Four new seep communities of Oligocene to Miocene age are reported from Venezuela. They consist mainly of large globular lucinid bivalves including Meganodontia, and moderately sized vesicomyid bivalves. After the late Miocene many large and typical 'Cenozoic' lucinid genera disappeared from the Caribbean seeps and are today known only from the central Indo-Pacific Ocean. We speculate that the increasingly oligotrophic conditions in the Caribbean Sea after the closure of the Isthmus of Panama in the Pliocene may have been unfavorable for such large lucinids because they

  19. Cenozoic Methane-Seep Faunas of the Caribbean Region

    PubMed Central

    Kiel, Steffen; Hansen, Bent T.

    2015-01-01

    We report new examples of Cenozoic cold-seep communities from Colombia, Cuba, the Dominican Republic, Trinidad, and Venezuela, and attempt to improve the stratigraphic dating of Cenozoic Caribbean seep communities using strontium isotope stratigraphy. Two seep faunas are distinguished in Barbados: the late Eocene mudstone-hosted ‘Joes River fauna’ consists mainly of large lucinid bivalves and tall abyssochrysoid gastropods, and the early Miocene carbonate-hosted ‘Bath Cliffs fauna’ containing the vesicomyid Pleurophopsis, the mytilid Bathymodiolus and small gastropods. Two new Oligocene seep communities from the Sinú River basin in Colombia consist of lucinid bivalves including Elongatolucina, thyasirid and solemyid bivalves, and Pleurophopsis. A new early Miocene seep community from Cuba includes Pleurophopsis and the large lucinid Meganodontia. Strontium isotope stratigraphy suggests an Eocene age for the Cuban Elmira asphalt mine seep community, making it the oldest in the Caribbean region. A new basal Pliocene seep fauna from the Dominican Republic is characterized by the large lucinid Anodontia (Pegophysema). In Trinidad we distinguish two types of seep faunas: the mudstone-hosted Godineau River fauna consisting mainly of lucinid bivalves, and the limestone-hosted Freeman’s Bay fauna consisting chiefly of Pleurophopsis, Bathymodiolus, and small gastropods; they are all dated as late Miocene. Four new seep communities of Oligocene to Miocene age are reported from Venezuela. They consist mainly of large globular lucinid bivalves including Meganodontia, and moderately sized vesicomyid bivalves. After the late Miocene many large and typical ‘Cenozoic’ lucinid genera disappeared from the Caribbean seeps and are today known only from the central Indo-Pacific Ocean. We speculate that the increasingly oligotrophic conditions in the Caribbean Sea after the closure of the Isthmus of Panama in the Pliocene may have been unfavorable for such large lucinids

  20. Anaerobic Oxidation of Methane at a Marine Methane Seep in a Forearc Sediment Basin off Sumatra, Indian Ocean

    PubMed Central

    Siegert, Michael; Krüger, Martin; Teichert, Barbara; Wiedicke, Michael; Schippers, Axel

    2011-01-01

    A cold methane seep was discovered in a forearc sediment basin off the island Sumatra, exhibiting a methane-seep adapted microbial community. A defined seep center of activity, like in mud volcanoes, was not discovered. The seep area was rather characterized by a patchy distribution of active spots. The relevance of anaerobic oxidation of methane (AOM) was reflected by 13C-depleted isotopic signatures of dissolved inorganic carbon. The anaerobic conversion of methane to CO2 was confirmed in a 13C-labeling experiment. Methane fueled a vital microbial community with cell numbers of up to 4 × 109 cells cm−3 sediment. The microbial community was analyzed by total cell counting, catalyzed reporter deposition–fluorescence in situ hybridization (CARD–FISH), quantitative real-time PCR (qPCR), and denaturing gradient gel electrophoresis (DGGE). CARD–FISH cell counts and qPCR measurements showed the presence of Bacteria and Archaea, but only small numbers of Eukarya. The archaeal community comprised largely members of ANME-1 and ANME-2. Furthermore, members of the Crenarchaeota were frequently detected in the DGGE analysis. Three major bacterial phylogenetic groups (δ-Proteobacteria, candidate division OP9, and Anaerolineaceae) were abundant across the study area. Several of these sequences were closely related to the genus Desulfococcus of the family Desulfobacteraceae, which is in good agreement with previously described AOM sites. In conclusion, the majority of the microbial community at the seep consisted of AOM-related microorganisms, while the relevance of higher hydrocarbons as microbial substrates was negligible. PMID:22207865

  1. Post depositional alteration of foraminiferal shells in cold seep settings: New insights from flow-through time-resolved analyses of biogenic and inorganic seep carbonates

    NASA Astrophysics Data System (ADS)

    Torres, Marta E.; Martin, Ruth A.; Klinkhammer, Gary P.; Nesbitt, Elizabeth A.

    2010-10-01

    Transient hydrocarbon migration within a sediment package leaves behind robust geological signatures in the biogenic and authigenic carbonate record. Here we apply Flow-Through Time Resolved Analyses (FT-TRA) to unravel the compositional changes in foraminifera from coastal fossil methane seeps exposed from Oregon to Vancouver Island: The Eocene-Oligocene Keasey Formation, the Oligocene-Miocene Pysht and Sooke Formations, and the Pliocene Quinault Formation. Our data show that secondary mineralization can be traced with the use of Mg/Ca ratios, which in altered foraminifera are significantly higher than the biogenic ratio (< 3 compared to values as high as 69 mol/mol). Analogous to the record in authigenic carbonate, secondary mineralization contains valuable information about seep characteristics and their geologic history. Data from the Quinault Formation reflect the influence of anaerobic oxidation of biogenic methane in both bleb (δ 13C: - 29.8‰ to - 14.0‰) and foraminiferal (δ 13C: - 43.0‰ to 2.0‰) carbonate. Oxygen isotopes from blebs and foraminifera indicate precipitation at bottom water temperatures in an environment comparable to conditions observed in modern seeps on the Oregon slope and elsewhere. The carbonates in these seeps are enriched in barium and strontium over biogenic values, and such elevated values may be used a diagnostic tool to identify methane-related carbonates. In contrast, in the Pysht and Sooke formations, carbonate precipitation (including secondary mineralization of foraminifera), was fueled by a thermogenic carbon source (δ 13C: - 14 to 3.4‰). These carbonates reflect a more complex paragenetic history and suggest alteration driven by post-depositional warm and/or meteoric fluids. The high manganese (up to 12 mmol/mol in foraminifera and 60.1 mmol/mol in a carbonate nodule) and low oxygen isotope values (δ 18O as low as - 7.7‰ in foraminifera and - 11.6‰ in a carbonate pavement) observed for the Pysht and Sooke

  2. Diverse sulfate-reducing bacteria of the Desulfosarcina/Desulfococcus clade are the key alkane degraders at marine seeps

    PubMed Central

    Kleindienst, Sara; Herbst, Florian-Alexander; Stagars, Marion; von Netzer, Frederick; von Bergen, Martin; Seifert, Jana; Peplies, Jörg; Amann, Rudolf; Musat, Florin; Lueders, Tillmann; Knittel, Katrin

    2014-01-01

    Biogeochemical and microbiological data indicate that the anaerobic oxidation of non-methane hydrocarbons by sulfate-reducing bacteria (SRB) has an important role in carbon and sulfur cycling at marine seeps. Yet, little is known about the bacterial hydrocarbon degraders active in situ. Here, we provide the link between previous biogeochemical measurements and the cultivation of degraders by direct identification of SRB responsible for butane and dodecane degradation in complex on-site microbiota. Two contrasting seep sediments from Mediterranean Amon mud volcano and Guaymas Basin (Gulf of California) were incubated with 13C-labeled butane or dodecane under sulfate-reducing conditions and analyzed via complementary stable isotope probing (SIP) techniques. Using DNA- and rRNA-SIP, we identified four specialized clades of alkane oxidizers within Desulfobacteraceae to be distinctively active in oxidation of short- and long-chain alkanes. All clades belong to the Desulfosarcina/Desulfococcus (DSS) clade, substantiating the crucial role of these bacteria in anaerobic hydrocarbon degradation at marine seeps. The identification of key enzymes of anaerobic alkane degradation, subsequent β-oxidation and the reverse Wood–Ljungdahl pathway for complete substrate oxidation by protein-SIP further corroborated the importance of the DSS clade and indicated that biochemical pathways, analog to those discovered in the laboratory, are of great relevance for natural settings. The high diversity within identified subclades together with their capability to initiate alkane degradation and growth within days to weeks after substrate amendment suggest an overlooked potential of marine benthic microbiota to react to natural changes in seepage, as well as to massive hydrocarbon input, for example, as encountered during anthropogenic oil spills. PMID:24722631

  3. Diverse sulfate-reducing bacteria of the Desulfosarcina/Desulfococcus clade are the key alkane degraders at marine seeps.

    PubMed

    Kleindienst, Sara; Herbst, Florian-Alexander; Stagars, Marion; von Netzer, Frederick; von Bergen, Martin; Seifert, Jana; Peplies, Jörg; Amann, Rudolf; Musat, Florin; Lueders, Tillmann; Knittel, Katrin

    2014-10-01

    Biogeochemical and microbiological data indicate that the anaerobic oxidation of non-methane hydrocarbons by sulfate-reducing bacteria (SRB) has an important role in carbon and sulfur cycling at marine seeps. Yet, little is known about the bacterial hydrocarbon degraders active in situ. Here, we provide the link between previous biogeochemical measurements and the cultivation of degraders by direct identification of SRB responsible for butane and dodecane degradation in complex on-site microbiota. Two contrasting seep sediments from Mediterranean Amon mud volcano and Guaymas Basin (Gulf of California) were incubated with (13)C-labeled butane or dodecane under sulfate-reducing conditions and analyzed via complementary stable isotope probing (SIP) techniques. Using DNA- and rRNA-SIP, we identified four specialized clades of alkane oxidizers within Desulfobacteraceae to be distinctively active in oxidation of short- and long-chain alkanes. All clades belong to the Desulfosarcina/Desulfococcus (DSS) clade, substantiating the crucial role of these bacteria in anaerobic hydrocarbon degradation at marine seeps. The identification of key enzymes of anaerobic alkane degradation, subsequent β-oxidation and the reverse Wood-Ljungdahl pathway for complete substrate oxidation by protein-SIP further corroborated the importance of the DSS clade and indicated that biochemical pathways, analog to those discovered in the laboratory, are of great relevance for natural settings. The high diversity within identified subclades together with their capability to initiate alkane degradation and growth within days to weeks after substrate amendment suggest an overlooked potential of marine benthic microbiota to react to natural changes in seepage, as well as to massive hydrocarbon input, for example, as encountered during anthropogenic oil spills. PMID:24722631

  4. Tracking California seafloor seeps with bathymetry, backscatter and ROVs

    NASA Astrophysics Data System (ADS)

    Orange, Daniel L.; Yun, Janet; Maher, Norman; Barry, James; Greene, Gary

    2002-11-01

    The California (USA) margin includes two different tectonic regimes: subduction north of the Mendocino Triple Junction and translation south. Both margins include seeps, and their distribution can be inferred using seafloor bathymetry and backscatter as well as subsurface seismic data. Anomalous bathymetric and backscatter features related to fluid expulsion include headless submarine canyons, fault zones, anticlines, pockmarks, and mud volcanoes. Anomalous backscatter may be caused by authigenic carbonate (related to the bacterial oxidation of methane) or cold seep clams—both have an impedance and roughness that may be higher than the surrounding seafloor. Remote-operated vehicle (ROV) dives to such suspect seep sites document the presence of extensive authigenic carbonate, areally restricted cold seep communities, carpets of chemoautotrophic bacteria, and bubbling gas. Our operations in the Monterey Bay, on the translational California margin, and the Eel River basin, on the convergent margin, indicate that bathymetric and backscatter maps of the seafloor, if sufficiently high resolution, can be used to map seep sites, and that the distribution of such seeps can be used to constrain subsurface conduits of fluid flow. ROVs, due to their combination of visualization, propulsion, manipulation, sonar, and navigation, provide an excellent platform for ground-truthing, mapping, and sampling seafloor seeps.

  5. Lipid Biomarkers Indicating Aerobic Methanotrophy at Ancient Marine Methane- Seeps

    NASA Astrophysics Data System (ADS)

    Birgel, D.; Peckmann, J.

    2007-12-01

    The inventory of lipid biomarkers of a number of ancient methane-seep limestones has been studied over the last decade. The molecular fingerprints of the chemosynthesis-based microbial communities tend to be extremely well-preserved in these limestones. The key process at seeps is the anaerobic oxidation of methane, performed by consortia of sulfate-reducing bacteria and methanotrophic archaea. Compounds preserved within modern and ancient seep settings comprise C-13-depleted lipid biomarkers. Besides the occurrence of C-13- depleted isoprenoids (archaea) and n-alkyl-chains (bacteria), C-13-depleted hopanoids have been reported in seep limestones. Here, lipid biomarker data are presented from three ancient methane-seep limestones embedded in Miocene and Campanian strata. These examples provide strong evidence that methane was not solely oxidized by an anaerobic process. In a Miocene limestone, 3-beta-methylated hopanoids were found (delta C-13: -100 per mil). Most likely, 3-beta-methylated hopanepolyols, prevailing in aerobic methanotrophs were the precursor lipids. In another Miocene limestone, a series of C-13-depleted 4-methylated steranes (lanostanes; -80 to -70 per mil) is derived from aerobic methanotrophs. Lanosterol is the most likely precursor of lanostanes, known to be produced by aerobic methanotrophs, some of which are outstanding among bacteria in having the capacity to produce steroids. In a Campanian seep limestone a suite of conspicuous secohexahydrobenzohopanes (-110 to -107 per mil) is found. These hopanoids probably represent early degradation products of seep-endemic aerobic methanotrophs. This interpretation is supported by the presence of "regular" hopanoids that can be discriminated from the unusual secohexahydrobenzohopanes by only moderately low delta C-13 values (-49 to -42 per mil). Structural and carbon isotope data reveal that aerobic methanotrophy is more common at ancient methane- seeps than previously noticed. Our data indicate that

  6. Pockmarks: self-scouring seep features?

    USGS Publications Warehouse

    Brothers, Laura L.; Kelley, Joseph T.; Belknap, Daniel F.; Barnhardt, Walter A.; Koons, Peter O.

    2011-01-01

    Pockmarks, or seafloor craters, occur worldwide in a variety of geologic settings and are often associated with fluid discharge. The mechanisms responsible for pockmark preservation, and pockmarks? relation to active methane venting are not well constrained. Simple numerical simulations run in 2-and 3-dimensions, and corroborated by flume tank experiments, indicate turbulence may play a role in pockmark maintenance, and, potentially, in pockmark excavation. Morphological analysis of the pockmarks indicates an abundance of flat-bottomed and/or elongated pockmarks. Pockmarks transition into furrows as the bay narrows and tidal flow is enhanced, providing unmistakable evidence of post-formation evolution. We hypothesize that some pockmarks formed from seafloor perturbations (e.g., gas or methane discharge), are1 maintained and gradually modified by vortical flow. This hypothesis provides a mechanism for pockmark preservation and enlargement without active fluid venting, which has implications for the interpretation of seafloor seep features in gas hydrates areas.

  7. Evidence and biogeochemical implications for glacially-derived sediments in an active margin cold seep

    USGS Publications Warehouse

    Pohlman, John W.; Riedel, Michael; Novosel, Ivana; Bauer, James E.; Canuel, Elizabeth A.; Paull, Charles K.; Coffin, Richard B.; Grabowski, Kenneth S.; Knies, David L.; Hyndman, Roy D.; Spence, George D.

    2011-01-01

    Delineating sediment organic matter origins and sediment accumulation rates at gas hydratebearing and hydrocarbon seeps is complicated by the microbial transfer of 13C-depleted and 14Cdepleted methane carbon into sedimentary pools. Sediment 13C and 14C measurements from four cores recovered at Bullseye vent on the northern Cascadia margin are used to identify methane carbon assimilation into different carbon pools. While the total organic carbon (TOC) is mostly unaltered and primarily terrigenous in origin, planktonic foraminifera and the bulk carbonate display evidence of methane overprinting. Mass balance models are applied to determine the extent to which methane overprinting increased the radiocarbon ages of the biogenic foraminifera. The corrected and calibrated foraminifera ages between sediment depths of 70 and 573 cm are from 14.9 to 15.9 ka BP, which coincides with the retreat of the late Quaternary Cordilleran Ice Sheet from Vancouver Island. Uniform TOC _13C values of -24.5 ± 0.5‰ from the upper 8 meters of sediment at Bullseye vent suggest all cored material is Pleistocene-derived glacimarine material deposited as the ice edge retreated landward. Bullseye vent is located within an uplifted sediment block isolated from turbidite deposition and has been a site of non-deposition since the ice sheet retreated from the shelf. Biogeochemical implications of seep sediments being dominated by aged, organic-poor (<0.4 wt% TOC) material are that methane is the primary energy source, and microbes directly and indirectly associated with the anaerobic oxidation of methane (AOM) will dominate the seep microbial community.

  8. Geochemistry of natural gases from mud volcanoes and surface gas seeps in NW-Columbia

    SciTech Connect

    Beeunas, M.A. ); Schoell, M. ); Beroiz, C. )

    1991-03-01

    Mud volcanoes and natural gas seeps are common in the southwest-northeast-trending Sinu Atlantico basin (SAB) and San Jacinto Fold Belt (SJFB) of NW-Colombia. The structural subunits are part of a highly complex active continental margin where the sediments become increasingly younger to the west from Late Cretaceous to Early Tertiary in the SJFB to Late Tertiary in the SAB. Some of the mud volcanoes are permanently active and form huge structures and are often aligned along major faults. Both seep and mud volcano gases are with low C{sub 2}-C{sub 4} and CO{sub 2} contents. Carbon and hydrogen isotope concentrations allow the subdivision into four groups of gas. These gases can be divided into four genetic based on their carbon and hydrocarbon isotope compositions. The isotopic variability of the different groups attests to the fact that very different gas-forming processes are or have been operating in the subsurface ranging from low-temperature thermogenesis. The various groups show, with few exceptions, a distinct regional distribution: Mud volcanoes and seeps with bacterial gases are restricted to the southern part of the SAB where the greatest thickness of young sediments is observed; gases of mixed thermogenic and bacterial origin are found in the coastal areas of the northern SAB; gases of thermogenic origin are predominantly observed in the SJFB; the thermogenic gases of Group 3 are restricted to two locations in the north of the SJFB. This regional association of genetic gas types with specific geotectonic units reflects different thermal histories of the respective tectonic areas and allowed the authors to delineate prospective areas for oil in NW-Colombia.

  9. Development of saline seeps in Southwestern United States

    USGS Publications Warehouse

    Johnson, Kenneth S.

    1994-01-01

    Saline seeps are an increasingly serious problem in semi-arid regions of the southwestern United States. They result when excessive recharge of the shallow ground water in soils raises the water table locally to within one meter of the land surface, and the salinity of the shallow water is increased through evaporation. In this connection, a comprehensive study is being undertaken in Oklahoma and Texas to determine the geologic setting, hydrology, soils, land use, and history of saline-seep development.

  10. Methane Seep Carbonates Host Distinct, Diverse, and Dynamic Microbial Assemblages

    PubMed Central

    Pasulka, Alexis L.; Marlow, Jeffrey J.; Grupe, Benjamin M.; Levin, Lisa A.

    2015-01-01

    ABSTRACT Marine methane seeps are globally distributed geologic features in which reduced fluids, including methane, are advected upward from the subsurface. As a result of alkalinity generation during sulfate-coupled methane oxidation, authigenic carbonates form slabs, nodules, and extensive pavements. These carbonates shape the landscape within methane seeps, persist long after methane flux is diminished, and in some cases are incorporated into the geologic record. In this study, microbial assemblages from 134 native and experimental samples across 5,500 km, representing a range of habitat substrates (carbonate nodules and slabs, sediment, bottom water, and wood) and seepage conditions (active and low activity), were analyzed to address two fundamental questions of seep microbial ecology: (i) whether carbonates host distinct microbial assemblages and (ii) how sensitive microbial assemblages are to habitat substrate type and temporal shifts in methane seepage flux. Through massively parallel 16S rRNA gene sequencing and statistical analysis, native carbonates are shown to be reservoirs of distinct and highly diverse seep microbial assemblages. Unique coupled transplantation and colonization experiments on the seafloor demonstrated that carbonate-associated microbial assemblages are resilient to seep quiescence and reactive to seep activation over 13 months. Various rates of response to simulated seep quiescence and activation are observed among similar phylogenies (e.g., Chloroflexi operational taxonomic units) and similar metabolisms (e.g., putative S oxidizers), demonstrating the wide range of microbial sensitivity to changes in seepage flux. These results imply that carbonates do not passively record a time-integrated history of seep microorganisms but rather host distinct, diverse, and dynamic microbial assemblages. PMID:26695630