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Southern End (southern + end)
Selected AbstractsTrophic role of Atlantic cod in the ecosystemFISH AND FISHERIES, Issue 1 2009Jason S. Link Abstract As the world's oceans continue to undergo drastic changes, understanding the role of key species therein will become increasingly important. To explore the role of Atlantic cod (Gadus morhua Gadidae) in the ecosystem, we reviewed biological interactions between cod and its prey, predators and competitors within six ecosystems taken from a broad geographic range: three are cod-capelin (Mallotus villosus Osmeridae) systems towards cod's northern Atlantic limit (Barents Sea, Iceland and Newfoundland,Labrador), two are more diverse systems towards the southern end of the range (North Sea and Georges Bank,Gulf of Maine), and one is a species-poor system with an unusual physical and biotic environment (Baltic Sea). We attempt a synthesis of the role of cod in these six ecosystems and speculate on how it might change in response to a variety of influences, particularly climate change, in a fashion that may apply to a wide range of species. We find cod prey, predators and competitors functionally similar in all six ecosystems. Conversely, we estimate different magnitudes for the role of cod in an ecosystem, with consequently different effects on cod, their prey and predator populations. Fishing has generally diminished the ecological role of cod. What remains unclear is how additional climate variability will alter cod stocks, and thus its role in the ecosystem. [source] Organic geochemistry indicates Gebel El Zeit, Gulf of Suez, is a source of bitumen used in some Egyptian mummiesGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 3 2005A.O. Barakat Molecular geochemical properties of crude oils and surface petroleum seeps from the southern part of the Gulf of Suez were evaluated. The characterizations of individual aliphatic, aromatic, and biomarker compounds were based on gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) analyses. The results provided strong evidence for a close genetic association of these samples. The geochemical characteristics suggest an origin from Tertiary source rocks deposited in a normal marine environment that received continental runoff. The molecular signatures of the investigated samples were very similar to those of the Lower Miocene Rudeis Formation source rock in the southern Gulf of Suez. Further, biomarker fingerprints of the investigated oil seeps were compared with those of the Dead Sea asphalt, as well as the bitumen from some Egyptian mummies reported in the literature. The results demonstrate that oil seeps from the southern end of Gebel El Zeit were used by ancient Egyptians for embalming. © 2005 Wiley Periodicals, Inc. [source] Three-dimensional elastic earthquake modelling based on integrated seismological and InSAR data: the Mw= 7.2 Nuweiba earthquake, gulf of Elat/Aqaba 1995 NovemberGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2003G. Shamir SUMMARY The Nuweiba earthquake (1995 November 22; Mw= 7.2), the largest seismic event along the Dead Sea Transform (DST) in at least 160 yr, ruptured 45,50 km along the Aragonese segment of the left-stepping strike-slip fault system occupying the gulf of Elat/Aqaba (southern segment of the DST). The rupture initiated in a partly normal, low-slip first subevent near the southern end of the fault and propagated unilaterally north-northeastward as a high-slip, nearly pure sinistral second subevent, which was responsible for over 90 per cent of the total seismic moment. The source mechanism and slip distribution, derived from inversion of teleseismic broad-band waveforms, are used to construct a 3-D elastic model of the earthquake based on the boundary elements method, resulting in the full 3-D displacement and stress fields induced by the earthquake. In the absence of sufficient Global Positioning System data, the only other constraints on the geometry and slip distribution of the rupture are provided by interferometric synthetic aperture radar (InSAR) measurements spanning the coseismic and early post-seismic period. We calculate simulated interferograms by transforming the calculated surface displacement field into the satellite coordinate system and comparing them with the observed interferograms. The model parameters are then iteratively modified until a best-fitting model is obtained, providing a refined set of static source parameters for the mainshock. This model is then used to calculate the static Coulomb stress changes induced by the mainshock on the step-over faults, suggesting that the major (Mw, 5) aftershocks in the first eight post-seismic months were triggered by small changes (<1 bar) in the left-lateral Coulomb stress, with effective friction coefficient not higher than 0.2. Aftershock distribution and mechanisms indicate that the available Coulomb stress dropped below the frictional strength of the fault but was not complete. [source] Stresses at sites close to the Nojima Fault measured from core samplesISLAND ARC, Issue 3-4 2001Kiyohiko Yamamoto Abstract The Nojima Fault in Awaji, Hyogo prefecture, Japan, was ruptured during the 1995 Hyogo-ken Nanbu earthquake (MJMA = 7.2). Toshima is located close to the fault segment, in which a large dislocation has been observed on the Earth's surface. Ikuha is near the southern end of the buried fault that extends from the surface rupture. Stresses are measured on core samples taken at depths of 310 m, 312 m and 415 m at Toshima and a depth of 351 m at Ikuha. The measured stresses show that both sites are in the field of a strike,slip regime, but compression dominates at Toshima. Defining the relative shear stress as the maximum shear stress divided by the normal stress on the maximum shear plane, the relative shear stress ranges from 0.42 to 0.54 at Toshima and is approximately 0.32 at Ikuha. While the value at Ikuha is moderate, those at Toshima are comparably large to those in areas close to the inferred fault of the 1984 Nagano-ken Seibu earthquake. Value amounts greater than 0.4 suggest that there are areas of large relative shear stress along faults, thus having the potential to generate earthquakes. Provided that the cores are correctly oriented, the largest horizontal stresses at shallow depths are in the direction from N113°E to N139°E at Toshima and N74°E at Ikuha, indicating that the fault does not orient optimally for the stress field at both sites. The slip is known to be predominant in the right-lateral strike,slip component. Although this slip may appear contradictory to the stress field at Toshima, the slip direction is found to be parallel to the measured stresses resolved on the fault plane for the first approximation. The ratio of shear stress to normal stress on the fault plane is roughly estimated to be greater than zero and smaller than 0.3 near Toshima. [source] The Indochinese,Sundaic zoogeographic transition: a description and analysis of terrestrial mammal species distributionsJOURNAL OF BIOGEOGRAPHY, Issue 5 2009David S. Woodruff Abstract Aim, We describe the distributions of mammal species between the Indochinese and Sundaic subregions and examine the traditional view that the two faunas show a transition near the Isthmus of Kra on the Thai,Malay peninsula. Location, Species distributions are described along a 2000-km transect from 20° N (northernmost Thailand) to 1° N (Singapore). Methods, For the 325 species of native non-marine mammals occurring along the transect we used published records to provide a database of their distributional records by degree of latitude. Results, Along the transect we found 128 Indochinese species with southern range limits, 121 Sundaic species with northern range limits, four un-assignable endemics and 72 widespread species. In total, 152 southern and 147 northern range limits were identified, and their distribution provides no evidence for a narrow faunal transition near the Isthmus of Kra (10°30, N) or elsewhere. Range limits of both bats and non-volant mammals cluster in northernmost peninsular Malaysia (5° N) and 800 km further north, where the peninsula joins the continent proper (14° N). The clusters of northern and southern range limits are not concordant but overlap by 100,200 km. Similarly, the range limits of bats and non-volant mammals cluster at slightly different latitudes. There are 30% fewer species and range limits in the central and northern peninsula (between 6 and 13° N), and 35 more widely distributed species have range gaps in this region. In addition, we found 70 fewer species at the southern tip of the peninsula (1° N) than at 3,4° N. Main conclusions, The deficiencies of both species and species range limits in the central and northern peninsula are attributed to an area effect caused by repeated sea-level changes. Using a new global glacioeustatic curve developed by Miller and associates we show that there were > 58 rapid sea-level rises of > 40 m in the last 5 Myr that would have resulted in significant faunal compression and local population extirpation in the narrow central and northern parts of the peninsula. This new global sea-level curve appears to account for the observed patterns of the latitudinal diversity of mammal species, the concentration of species range limits north and south of this area, the nature and position of the transition between biogeographical subregions, and possibly the divergence of the faunas themselves during the Neogene. The decline of species diversity at the southern end of the transect is attributed to a peninsula effect similar to that described elsewhere. [source] Cross-cutting moraines reveal evidence for North Atlantic influence on glaciers in the tropical Andes,JOURNAL OF QUATERNARY SCIENCE, Issue 3 2010Jacqueline A. Smith Abstract Surface exposure dating of boulders on an exceptionally well-preserved sequence of moraines in the Peruvian Andes reveals the most detailed record of glaciation heretofore recognised in the region. The high degree of moraine preservation resulted from dramatic changes in the flow path of piedmont palaeoglaciers at the southern end of the Cordillera Blanca (10° 00, S, 77° 16, W), which, in turn, generated a series of cross-cutting moraines. Sixty 10Be surface exposure ages indicate at least four episodes of palaeoglacier stabilisation (>65, ca. 65, ca. 32 and ca. 18,15,ka) and several minor advances or stillstands on the western side of the Nevado Jeulla Rajo massif. The absence of ages close to the global Last Glacial Maximum (ca. 21,ka) suggests that if an advance culminated at that time any resulting moraines were subsequently overridden. The timing of expanded ice cover in the central Peruvian Andes correlates broadly with the timing of massive iceberg discharge (Heinrich) events in the North Atlantic Ocean, suggesting a possible causal connection between southward migration of the Intertropical Convergence Zone during Heinrich events and a resultant increase in precipitation in the tropical Andes. Copyright © 2010 John Wiley & Sons, Ltd. [source] The Sirente crater field, ItalyMETEORITICS & PLANETARY SCIENCE, Issue 11 2002Jens ORMö They are located in the Sirente plain within the mountains of the Abruzzo region, central Italy. The craters are distributed in a field 450 m long and 400 m wide. This field consists of ,17 smaller craters close to a larger main crater. The main crater is located in the southern end of the crater field and is 140 m long and 115 m wide, measured rim-to-rim. It has a well-developed, saddle-shaped rim that rises at a maximum 2.2 m above the surrounding plain. Radiocarbon dating of the target surface preserved below the rim gave a calibrated age of formation at about a.d. 412 (1650 ± 40 radiocarbon years b.p.). This young age is consistent with the apparent little modification of the rim. The morphology of the main crater and its relation to a crater field strongly points to its origin by impact from a projectile that broke up during its passage through the atmosphere. Quartz is very rare in the target and no planar deformation features have been found so far. The rim material and the upper 4 m of the main crater infill are impregnated with ferric oxides, which gives a more reddish colour compared to the other sediments of the plain. Rusty crusts with high Fe and Mn content occur in the rim material, but have not been found in the plain's sediments. Some of these crusts can be separated by magnet, and have sporadic micron-sized Ni-rich granules. The main crater is in the size range of the craters with explosive dispersion of the projectile and has many features comparable to both large experimental and meteoritic impact craters formed in loose sediments. We suggest that this crater represents a rare example of well-preserved, small impact crater formed in unconsolidated target materials. [source] Current and historical patterns of drainage connectivity in eastern Australia inferred from population genetic structuring in a widespread freshwater fish Pseudomugil signifer (Pseudomugilidae)MOLECULAR ECOLOGY, Issue 2 2004B. B. M. Wong Abstract Dispersal can play an important role in the genetic structuring of natural populations. In this regard, freshwater fishes often exhibit extensive population genetic subdivision and are ideal subjects for investigating current and historical patterns of connection and dissociation between drainages. We set out to generate a comprehensive molecular phylogeny for a widespread freshwater fish from eastern Australia, the Pacific blue-eye Pseudomugil signifer. Although movement via flood events may be important in the southern end of the species' range, genetic structuring revealed the importance of historical drainage connections and dissociations in mediating or disrupting dispersal. A dominant feature of our phylogeny is a split between northern and southern populations, which appears to be congruent with a biogeographical barrier recently implicated as important for the connectivity of freshwater organisms in eastern Australia. The extent of the split also has taxonomic implications consistent with suggestions that the Pacific blue-eye may represent more than a single species. [source] Spatial distribution of vectors of Ross River virus and Barmah Forest virus on Russell Island, Moreton Bay, QueenslandAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2002Jason AL Jeffery Abstract We used a network of 20 carbon dioxide- and octenol-supplemented light traps to sample adult mosquitoes throughout Russell Island in southern Moreton Bay, south-east Queensland. Between February and April 2001, an estimated 1365 564 adult female mosquitoes were collected. In contrast to an average catch of 9754 female mosquitoes per trap night on Russell Island, reference traps set on Macleay Island and on the mainland returned average catches of 3172 and 222, respectively. On Russell Island, Ochlerotatus vigilax (Skuse), Coquillettidia linealis (Skuse), Culex annulirostris Skuse and Verrallina funerea (Theobald), known or suspected vectors of Ross River (RR) and/or Barmah Forest (BF) viruses, comprised 89.6% of the 25 taxa collected. When the spatial distributions of the above species were mapped and analysed using local spatial statistics, all were found to be present in highest numbers towards the southern end of the island during most of the 7 weeks. This indicated the presence of more suitable adult harbourage sites and/or suboptimal larval control efficacy. As immature stages and the breeding habitat of Cq. linealis are as yet undescribed, this species in particular presents a considerable impediment to proposed development scenarios. The method presented here of mapping the numbers of mosquitoes throughout a local government area allows specific areas that have high vector numbers to be defined. [source] | ||||||||||||||||