955 resultados para hydroxyl-terminated polybutadiene
Resumo:
The tissue-specific composition of sum classes of brominated and chlorinated contaminants and metabolic/degradation byproducts was determined in adult male and female polar bears from East Greenland. Significantly (p < 0.05) higher concentrations of SUM-PCBs, various other organochlorines such as SUM-CHL, p,p'-DDE, SUM-CBz, SUM-HCHs, octachlorostyrene (OCS),SUM-mirex, dieldrin, the flame retardants SUM-PBDEs, and total-(R)-hexabromocyclododecane (HBCD), SUM-methylsulfonyl (MeSO2)-PCBs and 3-MeSO2-p,p'-DDE, were found in the adipose and liver tissues relative to whole blood and brain. In contrast, SUM-hydroxyl (OH)-PCB, 4-OH-heptachlorostyrene and SUM-OH-PBDE concentrations were significantly highest (p < 0.05) in whole blood, whereas the highest concentrations of SUM-OH-PBBs were found in the adipose tissue. Based on the total concentrations of all organohalogens in all three tissues and blood, the combined body burden was estimated to be 1.34 ± 0.12 g, where >91% of this amount was accounted for by the adipose tissue alone, followed by the liver, whole blood, and brain. These results show that factors such as protein association and lipid solubility appear to be differentially influencing the toxicokinetics, in terms of tissue composition/localization and burden, of organohalogen classes with respect to chemical structure and properties such as the type of halogenation (e.g., chlorination or bromination), and the presence or absence of additional phenyl group substituents (e.g., MeO and OH groups). The tissue- and blood-specific accumulation (or retention) among organohalogen classes indicates that exposure and any potential contaminant-mediated effects in these polar bears are likely tissue or blood specific.
Resumo:
Determination of when and where animals feed and how much they consume is fundamental to understand their ecology and role in ecosystems. However, the lack of reliable data on feeding habits of wild animals, and particularly in marine endotherms, attests to the difficulty in doing this. A promising recent development proposes using a Hall sensor-magnet System - the inter-mandibular angle sensor (IMASEN) attached to animals' jaws to elucidate feeding events. We conducted trials on captive pinnipeds by feeding IMASEN-equipped animals with prey to examine the utility of this system. Most feeding events were clearly distinguishable from other jaw movements; only small prey items might not be resolved adequately. Based on the results of this study we examined feeding events from free-ranging Weddell seals fitted with IMASENs and dead-reckoners during December 2003 at Drescher Inlet (Riiser Larsen Ice Shelf, eastern Weddell Sea coast), and present data on prey capture and ingestion in relation to the three-dimensionalmovement patterns of the seals. A total of 19 Weddell seals were immobilised by using a combination of ketamine, xylazine, and diazepam. Eight seals were drugged once, six two times, and two and three were drugged three and four times each, coming to a total of 38 immobilisation procedures. Narcoses were terminated with yohimbine (doi:10.1594/PANGAEA.438931).
Resumo:
Corticosterone, the main stress hormone in birds, mediates resource allocation, allowing animals to adjust their physiology and behaviour to changes in the environment. Incubation is a time and energy-consuming phase of the avian reproductive cycle. It may be terminated prematurely, when the parents' energy stores are depleted or when environmental conditions are severe. In this study, the effects of experimentally elevated baseline corticosterone levels on the parental investment of incubating male Adelie penguins were investigated. Incubation duration and reproductive success of 60 penguins were recorded. The clutches of some birds were replaced by dummy eggs, which recorded egg temperatures and rotation rates, enabling a detailed investigation of incubation behaviour. Corticosterone levels of treated birds were 2.4-fold higher than those of controls 18 days post treatment. Exogenous corticosterone triggered nest desertion in 61% of the treated birds; consequently reducing reproductive success, indicating that corticosterone can reduce or disrupt parental investment. Regarding egg temperatures, hypothermic events became more frequent and more pronounced in treated birds, before these birds eventually abandoned their nest. The treatment also significantly decreased incubation temperatures by 1.3 °C and lengthened the incubation period by 2.1 days. However, the number of chicks at hatching was similar among successful nests, regardless of treatment. Weather conditions appeared to be particularly important in determining the extent to which corticosterone levels affected the behaviour of penguins, as treated penguins were more sensitive to severe weather conditions. This underlines the importance of considering the interactions of organisms with their environment in studies of animal behaviour and ecophysiology.
Resumo:
Adult male and female Weddell seals (Leptonychotes weddellii) were fitted with Time-depth recorders (TDR) at Drescher Inlet (Riiser Larsen Ice Shelf), eastern Weddell Sea coast, in February 1998. Eight of 15 data sets were selected for analyses to investigate the seals' foraging behaviour (doi:10.1594/PANGAEA.511465, doi:10.1594/PANGAEA.511454, doi:10.1594/PANGAEA.511456, doi:10.1594/PANGAEA.511457, doi:10.1594/PANGAEA.511459, doi:10.1594/PANGAEA.511462, doi:10.1594/PANGAEA.511466, doi:10.1594/PANGAEA.511467). These data sets provided simultaneous dive records of eight seals over eight days. The seals primarily foraged within two depth layers, these being from the sea surface to 160 m where temperature and salinity varied considerably, and from 340 to 450 m near the bottom where temperature was lowest and salinity highest, with little variation. While pelagic and benthic diving occurred during daylight, the seals foraged almost exclusively in the upper water column at night. Trawling during daytime confirmed that Pleuragramma antarcticum were by far the most abundant fish both in the pelagial and close to the bottom. Pelagic night-hauls at 110-170 m depth showed highly variable biomass of P. antarcticum with a peak at around midnight. The temporal changes in the local abundance of P. antarcticum, particularly in the pelagial, may explain the trends in the seals' pelagic and benthic foraging activities. This is the first study which describes the jaw movements of a hunting seal which are presumably indicative of feeding events. Trophic links from the Weddell seal to fish, zooplankton and krill, Euphausia superba, are discussed. Another seven data sets did not overlap substantially with the selected time frame (doi:10.1594/PANGAEA.511458, doi:10.1594/PANGAEA.511460, doi:10.1594/PANGAEA.511464, doi:10.1594/PANGAEA.511468, doi:10.1594/PANGAEA.511469, doi:10.1594/PANGAEA.511453, doi:10.1594/PANGAEA.511463). A total of 25 Weddell seals were immobilised during the study period using a combination of ketamine, xylazine, and diazepam. Seven seals were drugged once, 15 seals two times, and three were drugged three times, coming to a total of 46 immobilisation procedures. Narcoses were terminated with yohimbine (doi:10.1594/PANGAEA.438933).
Resumo:
Ocean Drilling Program Site 975 is located near the base of the Menorca Rise in the South Balearic Basin of the western Mediterranean Sea. Coring at this site penetrated the Pliocene/Miocene boundary and recovered a sequence of sediments that represent the final stages of salt deposition and the transition from evaporitic to open marine conditions at the end of the Miocene (Messinian). Detailed petrographic observations and bulk mineralogical analyses by X-ray diffraction form the basis for preliminary interpretations of depositional environments for this section. Gypsum is thought to have been deposited in an evaporating basin below wave base. Cycles consisting of a clay layer overlain by gypsiferous chalk, laminated gypsum, and finally pinch-and-swell gypsum suggest upsection increases in salinity. The gypsum section is overlain by two exotic sand layers thought to mark events of fresher water (marine or meteoric) inflow to the basin. Gypsum deposition terminated and was replaced by inorganic precipitation of micritic calcite with periodic, variable dilution by fine-grained terrigenous sediment. The micritic sediments have fine, slightly wavy, laminations indicating either an algal/microbial mat origin, or varve-like fluctuations in deposition, perhaps in a deep basin. The Pliocene/Miocene boundary falls within an interval of banded micritic silty clays that reflect the final environmental fluctuations during the transition to the open marine conditions of the Pliocene.
Resumo:
Site 536 terminated in a shallow-water dolomite of unknown age. Paleomagnetic measurements combined with strontium isotope analyses suggest that the dolomite was deposited in the Middle Jurassic to Early Cretaceous time interval. However, the assumptions required to reach this determination make these results less than conclusive.
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In the blood of Antarctic notothenioid and Arctic gadiform fishes, freezing is inhibited by antifreeze glycopeptide macromolecules (AFGP). These antifreeze molecules are built up of repeating tripeptide units (Ala-Ala-Thr)n, to which the disaccharide fl-D-galactosyl-(1->3)a-N-acetyl-D-galactosamine is linked through the hydroxyl oxygen of the threonyl residue. Species of Liparididae, Zoarcidae, Cottidae and Pleuronectidae synthezise only unglycosylated antifreeze peptides (AFP). It could be demonstrated for the Antarctic silverfish Pleuragramma antarcticum that the synthesis of AFGP is not constitutive but rather regulated by water temperature. Moreover a novel glycopeptid was isolated and characterised from P. antarcticum, the Pleuragramma-antifreeze glycopeptid (PAGP). The level of antifreeze concentration was dependent on the ambient water temperature, the depth of distribution, the life cycle and the evolution of the species. Surprisingly, detectable AFGPs in perciform fish of the Antarctic and gadiform fish of the Arctic and Antarctic could illustrate, that before the continental drift occurred a precursor glycopeptid existed, and that the existence of freezing resistance in some species reflects the past glaciation. The wide distribution and high heterogeneity of AFPs point to the assumption that these peptides are results of cold shock stress responses.
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The benthic foraminifer fauna at Sumisu Rift Sites 790 and 791 indicates that a deep open-ocean (>2300 m) or a basin with open-ocean access existed between 1.1 and 0.7 Ma at the time of the initiation of rifting. The appearance of a low- to medium-oxygen fauna (1600-2300 m) between 0.7 and 0.5 Ma suggests that the open-ocean access may have been terminated at this time because of the development of volcanoes and rift flank uplifts around the basin. The occurrence of low-oxygen faunas at 0.03 Ma suggests a secondary closing of the basin. The lower bathyal benthic faunas from lower Pliocene sediments of rift margin Site 788 suggest about 0.6-1.6 km of total basement uplift. This uplift may have led to the formation of the major hiatus between 2.3 and <0.3 Ma. The faunal changes of benthic foraminifers at Sites 792 and 793 in the forearc basin document a shallowing water depth from below the carbonate compensation depth (CCD) (about 3.5 km) in the late early Oligocene to the present depths of 1800 and 2975 m, respectively. These data suggest about 1 km of total basement uplift in the inner part of the forearc basin (Site 792) and about 0.6 km total basement subsidence in the central part of the forearc basin (Site 793) since about 31 Ma. The former uplift led to a thinner sediment accumulation (800 m) and the latter subsidence to a thicker sediment accumulation (1400 m) at these sites. Faunal changes of benthic foraminifers observed in Sites 782 and 786 sequences drilled at the outer-arc high document a deepening water depth from 1.3 to 2.1 km in late Eocene to the present depth of about 3 km. These data suggest about 1.1-1.9 and 1.3-2.1 km of total basement subsidence at Sites 786 and 782, respectively. These results indicate total basement uplift in the inner part of the Bonin arc-trench system since late Oligocene and total basement subsidence in the outer part of the system since late Eocene. The last occurrence (LO) of Stilostomella spp. and Pleurostomella spp. and the first occurrence (F0) of Bulimina aculeata d'Orbigny occurred consistently at 0.7 Ma at all three arc proximal sites (790,791, and 792). This fact is taken to suggest a change of water mass, from one originating from the central part of the ocean to that originating from ocean-margin areas at that time.
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A sediment core from the western tropical Atlantic covering the last 21,000 yr has been analysed for centennial scale reconstruction of sea surface temperature (SST) and ice volume-corrected oxygen isotopic composition of sea water (delta18O(ivc-sw)) using Mg / Ca and delta18O of the shallow dwelling planktonic foraminifer Globigerinoides ruber (white). At a period between 15.5 and 17.5 kyr BP, the Mg / Ca SST and delta18O(ivc-sw), a proxy for sea surface salinity (SSS), reveals a warming of around 2.5 °C along with an increase in salinity. A second period of pronounced warming and SSS increase occurred between 11.6 and 13.5 kyr BP. Within age model uncertainties, both warming intervals were synchronous with air temperature increase over Antarctica and ice retreat in the southern South Atlantic and terminated with abrupt centennial scale SSS decrease and slight SST cooling in conjunction with interglacial reactivation of the meridional overturning circulation (MOC). We suggest that during these warm intervals, production of saline and warm water of the North Brazil Current resulted in pronounced heat and salt accumulation, and was associated with warming in the southern Atlantic, southward displacement of the intertropical convergence zone and weakened MOC. At the termination of the Younger Dryas and Heinrich event 1, intensification of cross-equatorial heat and salt transport caused centennial scale cooling and freshening of the western tropical Atlantic surface water. This study shows that the western tropical Atlantic served as a heat and salt reservoir during deglaciation. The sudden release of accumulated heat and salt at the end of Younger Drays and Heinrich event 1 may have contributed to the rapid reinvigoration of the Atlantic MOC.
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Lithobiostratigraphic data indicate that the double reflectors on the seismic profile through Ocean Drilling Program (ODP) Site 1148 represent two unconformities that coincide, respectively, with the lower/upper Oligocene boundary at ~488 mcd, and Oligocene-Miocene boundary at 460 mcd. Two other unconformities, at ~478 and 472 mcd, respectively, were also identified within the upper Oligocene section. Together they erased a sediment record of about 3 Ma from this locality in a period of very active seafloor spreading. The existence of 32.8 Ma marine sediment at the terminated depth (850 mcd) indicates that the initial breakup of the South China Sea (SCS) was probably during 34-33 Ma, close to the Eocene-Oligocene boundary. High sedimentation rates of 60-115 m/my from the much expanded, N350 m lower Oligocene section resulted from rifting and rapid subsidence between 33 and 29 Ma. The mid-Oligocene unconformity at ~28.5 Ma, which also occurred in many parts of the Indo-West Pacific region, was probably related to a significant uplift of the Himalayan-Tibetan Plateau to the west and the initial collision between Indonesia and Australia in the south. A narrowed Indonesian seaway may have accounted for the late Oligocene warming and chalk deposition in the northern South China Sea including the Site 1148 locality. The unconformities and slumps near the Oligocene-Miocene boundary indicate a very unstable tectonic regime, probably corresponding to changes in the rotation of different land blocks and the seafloor spreading ridge from nearly E-W to NE-SW, as recognized earlier at magnetic Anomaly 7. This 25 Ma event also saw the first New Guinea terrane docking at the northern Australian craton. The low sedimentation rate of ~15 m/my in the early to middle Miocene may correspond to another period of rapid seafloor spreading and rapid widespread subsidence that effectively caused sediment source areas to retreat with a rapidly rising sea level. The isostatic nature of these late Oligocene unconformities and slumps with several major collision-uplift events indicate that the rapid changes in the early evolutionary history of the South China Sea were mainly responding to regional tectonic reconfiguration including the uplift-driven southeast extrusion of the Indochina subcontinent.
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During the fourth Antarctic voyage ANT-IV of the research icebreaker POLARSTERN standard meteorological measurements have been performed. The measurements include 3-hourly synoptic observations as well as daily upper air soundings. The measurements started on September 6 1985 at Bremerhaven and were terminated at April 28 1986 in Punta Arenas. The 3-hourly synoptic observations are performed following the instructions of the FM 13 ships code defined by the World Meteorological Organization (WMO). The datasets include automatic measurements such as mean ship's speed, wind velocity, wind direction, air temperature, water temperature as well as visual observations such as total cloud amount, present weather, clouds, height and period of swell waves, ice classification. The visual observation are not performed during night time. For the upper air soundings VAISALA RS80 radiosondes, carried by helium-filled balloons (TOTEX 350 - 1500) were used. Data reception and evaluation were carried out by a MicroCora System (VAISALA). The upper air soundings include profile measurements of pressure, temperature, relative humidity and wind vector. Usually the soundings started at the heliport (10 m above sea level) and terminated between 15 and 37 km. The height of the measurements was calculated by applying the barometric formula. The wind vector was determined with the aid of the OMEGA navigation system.
Resumo:
Major-element compositions (Cl-, SO4[2-], Ca2+, Mg2+ , Li+ , K+, Na+ , Sr2+) of interstitial waters obtained from sediment cores along the ODP Leg 110 transect across the Northern Barbados accretionary prism have shown that a complex set of geochemical processes are of importance in this area. In the volcanic ash-rich Pleistocene-Pliocene sediments, alteration reactions involving volcanic ash lead to depletions of Mg2+ and K+. This process is confirmed by the much lower than contemporaneous seawater values of the 87Sr/86Sr ratios of dissolved strontium. In the deeper sediments recovered below the zone of decollement (Sites 671 and 672) large increases in Ca2+ and gradual decreases in Mg2+ , Na+, and d18O (H2O) indicate a potential contribution to the interstitial water chemistry by exchange with underlying basement rocks. This process has been hard to confirm because the drill holes were terminated well short of reaching basement. However, the concentration gradient pattern is consistent with observations in a large number of DSDP drill holes. Finally, but most importantly, low Cl- concentrations in the decollement zone and underlying sand layers, as well as in fault zones at Sites 673 and 674, indicate dilution of interstitial waters. The potential origins of the low Cl- concentrations are discussed, though we are not able to distinguish any mechanism in particular. Our evidence supports the concept of water migration along the decollement and through the underlying sandstones as well as along recent fault zones in the accretionary complex. Interstitial water concentration depth profiles are affected by faulting, thrusting, and overturn processes in the accretionary prism. These processes have caused a diminished diffusive exchange with the overlying ocean, thus explaining increased depletions in Mg2+ and SO4[2-] in sites farther onto the accretionary prism.
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A preliminary composite depth section was generated for Site 704 by splicing Holes 704A and 704B together over the interval 0-350 mbsf (0-9 m.y.). High-resolution carbonate and opal data from the cores were correlated with the calcium and silicon signals from the GST logging run in Hole 704B to identify missing and disturbed intervals in the cores. Paleomagnetic and biostratigraphic age boundaries were then transferred to the composite depth records to obtain an age model, and sedimentation rates were calculated by linear interpolation between datums. Algorithms relating measured dry-bulk density to carbonate content and depth were generated to produce predicted values of density for every sample. Accumulation rates of bulk, carbonate, opal, and terrigenous sediment components were then computed to generate a record of sediment deposition on the Meteor Rise that has a resolution of better than 200,000 yr for the period from 8.6 to 1.0 m.y. From 8.6 to 2.5 m.y., bulk-accumulation rates on the Meteor Rise averaged less than 2 g/cm**2/1000 yr and were dominated by carbonate deposition. The first significant opal deposition (6.0 m.y.) punctuated a brief (less than 0.6 Ma) approach of the Polar Front Zone (PFZ) northward that heralded a period of increasing severity of periodic carbonate dissolution events (terrigenous maxima) that abruptly terminated at 4.8 m.y. (base of the Thvera Subchron), synchronous with the reflooding of the Mediterranean after the Messinian salinity crisis. From 4.8 to 2.5 m.y., carbonate again dominated deposition, and the PFZ was far south except during brief northward excursions bracketing 4.2-3.9, 3.3-2.9, and 2.8-2.7 m.y. At 2.5 m.y., all components of bulk-accumulation rates increased dramatically (up to 15 g/cm2/1000 yr), and by 2.4 m.y., a pattern of alternating, high-amplitude carbonate and opal cyclicity marked the initiation of rapid glacial to interglaci·l swings in the position of the PFZ, synchronous with the "onset" of major Northern Hemisphere glaciation. Both mass-accumulation rates and the amplitude of the cycles decreased by about 2 m.y., but opal accumulation rates remained high up through the base of the Jaramillo (0.98 m.y.). From 1.9 to 1 m.y., the record is characterized by moderate amplitude fluctuations in carbonate and opal. This record of opal accumulation rates is interpreted as a long-term "Polar Front Indicator" that monitors the advance and retreat of the opal-rich PFZ northward (southward) toward (away from) the Meteor Rise in the subantarctic sector of the South Atlantic Ocean. The timing of PFZ migrations in the subantarctic South Atlantic Ocean is remarkably similar to Pliocene-Pleistocene climate records deduced from benthic oxygen isotope records in the North Atlantic Ocean (Raymo et al., 1989, doi:10.1029/PA004i004p00413; Ruddiman et al., 1989, doi:10.1029/PA004i004p00353). These include northward migrations during "cold" intervals containing strong glacial isotope stages (2.4-2.3, 2.1-2.0, 1.95-1.55, 1.45-1.30 m.y. and at about 1.13 and 1.09 m.y.) and southward migrations during "warm" intervals containing weak glacial and/or strong interglacial stages (2.45-2.40, 2.30-2.10, 2.00-1.95, 1.52-1.45, 1.30-1.18, 1.11, and 1.06-0.93 m.y.). Although our preliminary composite record is not continuous (some stages are obviously missing), there is hope that future work will identify these missing intervals in the as yet incomplete Hole 704B and will extend this high-resolution Southern Hemisphere climate record back to 8.6 m.y.
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Knowing the extent of the West Antarctic Ice Sheet (WAIS) at the Last Glacial Maximum (LGM) is crucial for initiating and calibrating numerical ice sheet models that can predict future ice-sheet change and contributions to sea level. However, empirical data are lacking for key areas of outer continental shelves, where the LGM-WAIS must have terminated. We present detailed marine geophysical and geological data documenting an up to ~12 m-thick sequence of glaciomarine sediments within a relict glacial trough in the outer parts of the Amundsen Sea Embayment. Continuous deposition must have persisted here since at least >40 ka BP, pre-dating the established LGM by >13,000 years. Observations constrain the LGM grounding line to a distinct grounding-zone wedge ~100 km inland from the continental shelf edge. Thus, a substantial shelf area (~6000 km**2) remained ice free through the last glacial cycle.