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Stable Isotope Evidence (stable + isotope_evidence)
Selected AbstractsStable isotope evidence for impala Aepyceros melampus diets at Akagera National Park, RwandaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Sandi R. Copeland Abstract Stable isotope analysis of tooth enamel was used to investigate the relative proportions of grass and browse in seasonal and overall diets of impala Aepyceros melampus at Akagera National Park, Rwanda. Bulk enamel samples suggest that on average, impala ate c. 86% C4 grass year-round, far more than in most previously studied impala populations across Africa. Intra-tooth samples show that seasonal changes in the proportion of C4 grass versus C3 browse are minimal (c. 10%), the diet being dominated by C4 grass year-round in contrast to other impala populations that consume ,50% browse during the dry season. Intra-tooth oxygen isotope values track carbon isotope changes to a moderate degree, but are not patterned clearly enough to permit identification of wet versus dry seasons. As other studies have shown that impala select high-protein diets, the foraging behaviour at Akagera is probably because of the availability of palatable grass for much of the year in the edaphic grasslands around the lacustrine environments of the eastern portions of Akagera National Park. Résumé L'analyse des isotopes stables de l'émail des dents a servi pour étudier les proportions relatives d'herbes et d'autres matières végétales dans le régime alimentaire saisonnier et général de l'impala Aepyceros melampus au Parc National de l'Akagera, au Rwanda. Des échantillons d'émail suggèrent qu'en moyenne, les impalas mangent c. 86% d'herbes de type C4 tout au long de l'année, beaucoup plus que la plupart des populations d'impalas étudiées ailleurs en Afrique. Les échantillons du centre des dents montrent que les changements saisonniers de la proportion d'herbes de type C4 par rapport au type C3 sont minimaux (c. 10%) et que le régime alimentaire est dominé par des herbes de type C4 toute l'année, contrairement aux autres populations d'impalas qui consomment ,50% d'autre végétation pendant la saison sèche. Les valeurs de l'isotope d'oxygène dans les dents permettent, dans une faible mesure, de détecter des changements de l'isotope de carbone, mais ils ne sont pas suffisamment définis pour permettre l'identification des saisons sèches ou humides. Comme d'autres études ont montré que les impalas sélectionnent une alimentation riche en protéines, le comportement alimentaire des impalas à l'Akagera est probablement dûà la disponibilité d'herbes goûteuses pendant une grande partie de l'année dans les prairies édaphiques qui entourent les environnements lacustres de l'est du Parc National de l'Akagera. [source] Stable isotope evidence for the consumption of millet and other plants in Bronze Age ItalyAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2009Mary Anne Tafuri Abstract Stable carbon and nitrogen isotope analysis was carried out on human and animal bones from four inland Early and Middle Bronze Age sites in Northern and Southern Italy. The main aims of the investigation were to explore the contribution of plant foods to the human diet and to examine any dietary differences between and within each of the sites. At two of the sites in Northern Italy, human and animal bones were significantly enriched in 13C. This finding was attributed to the consumption of domestic millets (Panicum miliaceum and/or Setaria italica), which are C4 pathway plants. Conversely, individuals from the two Bronze Age sites in Southern Italy were significantly depleted in 13C compared to those from the north. Here, millet was absent from the diet, and protein from C3 plants made a much greater dietary contribution than animal protein. This finding highlights the importance of cereal cultivation, most likely of wheat and barley, in the south of Italy during the Bronze Age. Overall, our results support the idea that the widespread cultivation of millet first occurred in Northern Italy, following its introduction from across the Alps in Central Europe. Finally, we found no significant differences in the stable isotope values between individuals at each site, when grouped by their sex or presence of grave goods. This leads to the conclusion that any status difference that may have existed is not reflected in the long-term dietary record, or at least not as measurable by stable isotope analysis. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source] Isotopic and petrological evidence of fluid,rock interaction at a Tethyan ocean,continent transition in the Alps: implications for tectonic processes and carbon transfer during early ocean formationGEOFLUIDS (ELECTRONIC), Issue 4 2007A. ENGSTRÖM Abstract We report overprinting stable isotope evidence of fluid,rock interaction below two detachment faults along which mantle rocks were exhumed to the seafloor, between the respective landward and seaward limits of oceanic and continental crust, at a Tethyan ocean,continent transition (OCT). This OCT, which is presently exposed in the Tasna nappe (south-eastern Switzerland) is considered an on-land analogue of the well-studied Iberian OCT. We compare our results with the fault architecture (fault core,damage zone,protolith) described by Caine et al. [Geology (1996) Vol. 24, pp. 1025,1028]. We confirm the existence of a sharp boundary between the fault core and damage zone based on isotopic data, but the boundary between the damage zone and protolith is gradational. We identify evidence for: (1) pervasive isotopic modification to 8.4 ± 0.1, which accompanied or post-dated serpentinization of these mantle rocks at an estimated temperature of 67,109°C, (2) either (i) partial isolation of some highly strained regions [fault core(s) and mylonite] from this pervasive isotopic modification, because of permeability reduction (Caine et al.) or (ii) subsequent isotopic modification caused by structurally channelled flow of warm fluids within these highly strained regions, because of permeability enhancement, and (3) isotopic modification, which is associated with extensive calcification at T = 54,100°C, primarily beneath the younger of the two detachment faults and post-dating initial serpentinization. By comparing the volumetric extent of calcification with an experimentally verified model for calcite precipitation in veins, we conclude that calcification could have occurred in response to seawater infiltration, with a calculated flux rate of 0.1,0.2 m year,1 and a minimum duration of 0.2,4.0 × 104 years. The associated time-averaged uptake flux of carbon during this period was 8,120 mol m,2 year,1. By comparison with the estimated area of exhumed mantle rocks at the Iberian OCT, we calculate a maximum annual uptake flux for carbon of 2,30 Tg year,1. This is an order of magnitude greater than that for carbon exchange at the mid-ocean ridges and 0.1,1.4% of the global oceanic uptake flux for carbon. [source] Carry-over effects in a Pacific seabird: stable isotope evidence that pre-breeding diet quality influences reproductive successJOURNAL OF ANIMAL ECOLOGY, Issue 2 2009Marjorie C. Sorensen Summary 1Understanding the interactions between different periods of the annual cycle in migratory animals has been constrained by our inability to track individuals across seasons. In seabirds, virtually nothing is known about how diet quality during the non-breeding period, away from the breeding grounds, might influence subsequent reproductive success. 2We used stable nitrogen (,15N) and carbon (,13C) isotopes to evaluate the effects of non-breeding diet quality on the timing of breeding and egg size in a population of Cassin's auklets (Ptychoramphus aleuticus) breeding on Triangle Island, British Columbia. Adult feathers are grown during two different periods of the annual cycle, which allowed us to estimate diet quality from the previous fall (October,November) and pre-breeding (February,March) period. 3We found that the estimated proportion of energetically superior copepods (Neocalanus spp.) in the pre-breeding diet tended to be higher in females that bred earlier and laid larger eggs, whereas energetically poor juvenile rockfish (Sebastes spp.) were dominant in the pre-breeding diets of females that bred later and laid smaller eggs. We detected no effect of fall diet quality on breeding date or egg size, and no effect of pre-breeding diet quality on breeding date in males. 4Pre-breeding diet quality was not related to body condition measured 1,2 days after laying, which suggests that females may need to attain a threshold condition before they initiate breeding and successfully rear young. 5Our results suggest that changes in climatic conditions during the pre-breeding period may have severe consequences for reproductive success by influencing breeding date and egg size. Our work emphasizes the importance of determining how events are linked throughout the annual cycle for understanding the fitness and population dynamics of migratory animals. [source] | ||||||||||