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  • 1
    Publication Date: 2021-05-19
    Description: The study of species' niches is becoming increasingly important in ecological research with the growing need to understand how species and their habitat respond to rapid environmental changes. This kind of study is especially challenging in the case of oceanic and cryptic species such as beaked whales. We analyzed δ¹³C and δ¹⁵N values in bone collagen to study interspecific variation in the isotopic niche of 8 species of beaked whales (Berardius arnuxii, Hyperoodon planifrons, Mesoplodon bowdoini, M. grayi, M. hectori, M. layardii, Tasmacetus shepherdi and Ziphius cavirostris) that stranded along the coast of Tierra del Fuego, Argentina, between 1967 and 2009. We found a spatial (e.g. feeding areas) and trophic (e.g. diet) isotopic segregation among these species, which are known to inhabit subantarctic to Antarctic waters. Iso-topic analysis showed that, while spatial segregation seems to operate to a higher degree in species of the same genus (e.g. Mesoplodon), trophic differentiation allowed the co-existence of sympatric species from different genera (e.g. Ziphius, Hyperodoon and Mesoplodon). Our results agree with previous studies based on stomach content analyses. In addition to different trophic strategies, variation in habitat preferences were also revealed by stable isotope analysis. An isotopic trend in both δ¹³C and δ¹⁵N values was found among beaked whales and possible prey species in accordance with previous information on other cetacean species known to have feeding areas in different ocean regions. The present study provides valuable ecological information about elusive and little-studied beaked whale species inhabiting the world's southernmost oceans.
    Description: Published
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed
    Format: pp.183-198
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  • 2
    Publication Date: 2021-05-19
    Description: We used stable carbon (δ13C) and nitrogen (δ15N) isotope analysis to investigate the trophic ecology of 8 small cetacean species of the southwestern South Atlantic Ocean: 6 delphinids (Grampus griseus, Lagenorhynchus cruciger, L. australis, Lissodelphis peronii, Pseudorca crassidens, and Cephalorhynchus commersonii) and 2 phocoenids (Phocoena dioptrica and P. spinipinnis). We also analyzed samples of possible prey collected from oceanic and coastal habitats adjacent to Tierra del Fuego. Cetacean bone-collagen δ13C and δ15N data revealed information on both habitat and prey preferences. We observed an isotopic continuum in which coastal species had the highest values of δ13C and δ15N (L. australis), while oceanic and southern species had the lowest values (L. cruciger and P. dioptrica), indicative of offshore foraging in cold oceanic waters near the Antarctic Conver- gence. Overlap in mean isotope values between C. commersonii and P. spinipinnis suggests that these species may have similar habitat and/or prey preferences. Isotope results for L. peronii, P. cras- sidens, and G. griseus suggest that at these latitudes (~54°S) they forage on the outer continental shelf. G. griseus show bimodal isotopic patterns, suggesting that 2 ecotypes that forage in different habitats and/or consume different prey items occur in this region of the southwestern Atlantic Ocean. The isotopic data presented here provide insight into the ecology of these cetaceans, with relevant implications for their successful management and conservation
    Description: Published
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed
    Format: pp.235-248
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  • 3
    Publication Date: 2021-05-19
    Description: Commerson's dolphins (Cephalorhynchus c. commersonii) and Peale's dolphins (Lagenorhynchus australis) are two of the most common species of cetaceans in the coastal waters of southwest South Atlantic Ocean. Both species are listed as Data Deficient by the IUCN, mainly due to the lack of information about population sizes and trends. The goal of this study was to build spatially explicit models for the abundance of both species in relation to environmental variables using data collected during eight scientific cruises along the Patagonian shelf. Spatial models were constructed using generalized additive models. In total, 88 schools (212 individuals) of Commerson's dolphin and 134 schools (465 individuals) of Peale's dolphin were recorded in 8,535 km surveyed. Commerson's dolphin was found less than 60 km from shore; whereas Peale's dolphins occurred over a wider range of distances from the coast, the number of animals sighted usually being larger near or far from the coast. Fitted models indicate overall abundances of approximately 22,000 Commerson's dolphins and 20,000 Peale's dolphins in the total area studied. This work provides the first large-scale abundance estimate for Peale's dolphin in the Atlantic Ocean and an update of population size for Commerson's dolphin. Additionally, our results contribute to baseline data on suitable habitat conditions for both species in southern Patagonia, which is essential for the implementation of adequate conservation measures.
    Description: Published
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed
    Format: pp.1-17
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  • 4
    ISSN: 0969-8043
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 4431-4437 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured a series of low-temperature transport parameters of AlGaAs/GaAs heterojunction transistors. The techniques used provide direct measurement of the two-dimensional electron gas on the same sample in which standard device characterization tools are applied. This creates an environment for devising and testing realistic device models. The apparent charge density is measured via both Hall and capacitance-voltage measurements and is compared with the two-dimensional electron gas charge measured via Shubnikov–de Haas conductivity oscillations. From this comparison we interpret the charge control of these gated heterojunction devices. Geometric magnetoresistance, magnetotransconductance, and Hall measurements of the mobility are presented and complications arising from the layered structure of the heterojunctions are discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry 43 (1951), S. 838-840 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Analysis of soil solution from forest sites dominated by Eucalyptus grandis and Eucalyptus maculata indicates that soluble forms of organic nitrogen (amino acids and protein) are present in concentrations similar to those of mineral nitrogen (nitrate and ammonium). Experiments were conducted to determine the extent to which mycorrhizal associations might broaden nitrogen source utilization in Eucalyptus seedlings to include organic nitrogen. In isolation, species of ectomycorrhizal fungi from northern Australia show varying abilities to utilize mineral and organic forms of nitrogen as sole sources. Pisolithus sp. displayed strongest growth on NH4+, glutamine and asparagine, but grew poorly on protein, while Amanita sp. grew well both on mineral sources and on a range of organic sources (e.g. arginine, asparagine, glutamine and protein). In sterile culture, non-mycorrhizal seedlings of Eucalyptus grandis and Eucalyptus maculata grew well on mineral sources of nitrogen, but showed no ability to grow on sources of organic nitrogen other than glutamine. In contrast, mycorrhizal seedlings grew well on a range of organic nitrogen sources. These observations indicate that mycorrhizal associations confer on species of Eucalyptus the ability to broaden their resource base substantially with respect to nitrogen. This ability to utilize organic nitrogen was not directly related to that of the fungal symbiont in isolation. Seedlings mycorrhizal with Pisolithus sp. were able to assimilate sources of nitrogen (in particular histidine and protein) on which the fungus in pure culture appeared to grow weakly. Experiments in which plants were fed 15N-labelled ammonium were undertaken in order to investigate the influence of mycorrhizal colonization on the pathway of nitrogen metabolism. In roots and shoots of all seedlings, 15N was incorporated into the amide group of glutamine, and label was also found in the amino groups of glutamine, glutamic acid, γ-aminobutyric acid and alanine. Mycorrhizal colonization appeared to have no effect on the assimilation pathway and metabolism of [15N]H4+; labelling data were consistent with the operation of the glutamate synthase cycle in plants infected with either Pisolithus sp. (which in isolation assimilates via the glutamate synthase cycle) or Elaphomyces sp. (which assimilates via glutamate dehydrogenase). It is likely that the control of carbon supply to the mycorrhizal fungus from the host may have a profound effect on both the assimilatory pathway and the range of nitrogen sources that can be utilized by the association.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We examined the stomachs of 25 false killer whales collected from a mass stranding of 181 animals along both coasts of the Strait of Magellan, Chile, in March 1989. The 21 stomachs (nine males and 12 females), with food remains contained 11 prey species (nine cephalopods and two fishes) with a total of 442 individuals. Except for one case, food remains were meager, indicating that the animals had not eaten for some time or through stress had vomited on the beach. Eleven of the 21 animals had mud (often with squid beaks) in the esophagus and first stomach. The prey were identified employing squid beaks, fish otoliths and bones, and their wet weights were estimated using regressions between hard parts and known weights of species. The most important prey were the oceanic and neritic-oceanic squids, Martialia byadesi and Illex argentinus, followed by the neritic fish, Macruronus magellanicus. Of less importance were the oceanic squid, Todaroes fillipovae, the oceanic and epipelagic octopus, Ocytboe sp., and the oceanic squid, Moroteuthis ingens. The rest of the prey were poorly represented and included four oceanic squids and one neritic fish. The prey species of these animals were subantarctic, with two antarctic species, abundant over the Patagonian shelf and adjacent oceanic waters around Tierra del Fuego.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 2 (1986), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 158 (1946), S. 675-676 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] MARTIN and co-workers1 extended their technique of partition chromatography of the amino-acids to the micro-scale by using filter paper instead of silica gel as the support for the stationary phase (water). We have found that the modified partition chromatogram for penicillin using buffer as the ...
    Type of Medium: Electronic Resource
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