Fine‐scale diet of the Australian sea lion (Neophoca cinerea) using DNA‐based analysis of faeces

We applied DNA‐based faecal analysis to determine the diet of female Australian sea lions (n = 12) from two breeding colonies in South Australia. DNA dietary components of fish and cephalopods were amplified using the polymerase chain reaction and mitochondrial DNA primers targeting the short (~100 base pair) section of the 16S gene region. Prey diversity was determined by sequencing ~50 amplicons generated from clone libraries developed for each individual. Faecal DNA was also combined and cloned from multiple individuals at each colony and fish diversity determined. Diets varied between individuals and sites. Overall, DNA analysis identified a broad diversity of prey comprising 23 fish and five cephalopod taxa, including many species not previously described as prey of the Australian sea lion. Labridae (wrasse), Monacanthidae (leatherjackets) and Mullidae (goat fish) were important fish prey taxa. Commonly identified cephalopods were Octopodidae (octopus), Loliginidae (calamary squid) and Sepiidae (cuttlefish). Comparisons of fish prey diversity determined by pooling faecal DNA from several samples provided a reasonable but incomplete resemblance (55–71%) to the total fish diversity identified across individual diets at each site. Interpretation of diet based on the recovery of prey hard‐parts identified one cephalopod beak (Octopus sp.) and one fish otolith (Parapriacanthus elongatus). The present study highlights the value of DNA‐based analyses and their capabilities to enhance information of trophic interactions.     

Evolution of sedimentary basins from the standpoint of petroleum origin and accumulation—an approach for a quantitative basin study

Generation, migration and accumulation of petroleum in a sedimentary basin is a function of geologic, hydrodynamic and thermodynamic development of the basin and the type and amount of organic matter. Temperature history not only determines rate of hydrocarbon generation, but also affects paleohydrodynamics and physical and thermal properties vs depth relationships. Therefore, paleotemperature is the most important parameter. Paleohydrodynamics together with geologic history of the basin is important in shaping secondary migration patterns and accumulation of hydrocarbons.Quantification of all the above processes is complicated. Steps in constructing a deterministic dynamic model for calculation of petroleum potential during a sedimentary basin development are stated and analyzed in this paper. The effect of paleotemperature variations on petroleum generation and on physical properties of sedimentary sequences are illustrated by numerical examples. Computer models will enable exploration geologists to make quantitative exploration predictions in sedimentary basins.     

Geo-Characterization at selected accelerometric stations in Crete (Greece) and comparison of earthquake data recordings with EC8 elastic spectra

To estimate the seismic response according to Eurocode (EC8) and almost all other national codes, site conditions have to be properly characterized so that soil amplification and the corresponding peak ground motion can be calculated. In this work, different geophysical and geotechnical methods are combined in order to define the detailed ground conditions in selected sites of the Hellenic Accelerometric Network (HAN) in Crete. For this purpose, the geological information of the sites and shear wave velocity, calculated from surface wave measurements, is used. Additionally, ground acceleration data recorded through HAN have been utilized from intermediate depth earthquakes in the broader area of South Aegean Sea. Using the recorded ground motion data and the procedure defined in EC8, the corresponding elastic response spectrum is calculated for the selected sites. The resulting information is compared to the values defined in the corresponding EC8 spectrum for the seismic zone that includes the island of Crete. The comparison shows that accurate definition of ground type through geological, geotechnical and geophysical investigations is important. However, our current comparison focuses on the distribution of values rather than the absolute values of EC8-prescribed spectra, and the results should be considered in this context.     

Environmental Geochemistry of Iron and Manganese in Six Himalayan Lakes

The distribution and abundance of iron and manganese, the two important mobile metals, in an aquatic environment have been presented. These metals play an important role in the binding of nutrients and toxic elements by virtue of their high specific area in the oxide form. The concentration of Fe ranged from 1.08 to 5.2 mg/g and that of Mn from 0.27 to 2.17 mg/g. The Dal lake sediments were rich in Fe and those of the Wular lake had the lowest mean concentration of Fe. It was observed that the smaller particle size fractions had a higher metal content in comparison to large size fractions. Data on the selective extraction of Fe and Mn and their accumulation in humus material have also been given.     

Some comments on physical processes at and near the tropopause

The major physical processes at and near the tropopause are evaluated; these processes are radiation, convection and turbulence, advection and vertical convergence. Calculations of instantaneous long wave radiative temperature change for observed and postulated moisture distributions show that radiation usually acts to smooth the temperature profile. Observations and the principle of continuity show that convection is infrequent and unimportant in establishing the tropopause. General principles and numerical integration of the heat conduction equation for special cases show that turbulence will act to smooth the temperature profile unless flux has a certain relationship to hydrostatic stability. Observations, calculations and the principle of continuity show that advection and vertical convergence cannot be universal mechanisms of tropopause formation.

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Zusammenfassung Die grundlegenden physikalischen Prozesse an und in der Nähe der Tropopause werden bestimmt; diese Prozesse sind Strahlung, Konvektion und Turbulenz, Advektion und Vertikalakonvergenz. Berechnungen von momentanen Temperaturänderungen durch langwellige Strahlung für beobachtete und vorgegebene Feuchtigkeitsverteilungen lassen erkennen, daß die Strahlung gewöhnlich das Temperaturprofil auszugleichen sucht. Beobachtungen und das Kontinuitätsprinzip zeigen, daß Konvektion selten und für die Bildung der Tropopause unwichtig ist. Allgemeine Prinzipien und numerische Integration der Wärmeleitungsgleichung für spezielle Fälle zeigen, daß die Turbulenz das Temperaturprofil auszugleichen sucht, außer wenn der Wärmestrom in spezieller Beziehung zur hydrostatischen Stabilität steht. Beobachtungen, Berechnungen und das Kontinuitätsprinzip führen zu der Feststellung, daß Advektion und vertikale Konvergenz nicht als allgemeine Mechanismen für die Bildung der Tropopause angesehen werden können.

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Résumé L'auteur évalue les processus physiques fondamentaux de la tropopause et à sa proximité; ces processus sont le rayonnement, la convection et la turbulence, l'advection et la convergence verticale. Le calcul de variations instantanées de la température dûes au rayonnement de grande longueur d'onde, par une distribution observée et supposée de l'humidité, montre qu'en général le rayonnement semble atténuer et égaliser le profil de la température. Les observations et le principe de continuité font admettre que la convection est rare et de peu d'importance pour la formation de la tropopause. Des principes généraux et une intégration numérique de l'équation de transmission de chaleur pour des can spéciaux montrent que la turbulence tend à égaliser le profil de température à moins que le flux de chaleur ne soit en relation spécifique avec la stabilité hydrostatique. Des observations, des calculs et le principe de continuité prouvent que l'advection et la convergence verticale ne peuvent être considérées comme étant des mécanismes généraux pour la formation de la tropopause.

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With 4 Figures

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The research reported here was supported in part by the Geophysical Research Directorate, A. F. Cambridge Research Center.     

Supraglacial melt channel networks in the Jakobshavn Isbræ region during the 2007 melt season

Supraglacial channels are an important mechanism for surface water transport over the ablation zone of western Greenland. The first assessment of the spatio‐temporal distribution of surface melt channels and their relationship to supraglacial lakes over the Jakobshavn Isbræ region of Western Greenland was analysed using Landsat Enhanced Thematic Mapper Plus panchromatic images during the 2007 melt season. A total of 1188 melt channels were delineated and show an increase in the number of melt channels throughout the season, reaching a peak on 9 August. Water‐filled melt channels advanced to a maximum elevation of 1647 m on 9 August and attained a minimum average slope of 0.009 on 8 July. The ablation zone demonstrates two hydrologic modes, where crevasse and moulin terminating channels dominate at elevations <800 m and higher‐order channel networks >800 m. Development of higher‐order networks is interrupted by flow divergence due to partitioning of melt water into vertical infiltration through moulins and crevasse fields prevalent at lower elevations. Tributary and connector networks between 800 and 1200 m in elevation are correlated with fewer lake occurrences, lower surface velocities (~50 m a^?1), and ice flow dominated by internal deformation over basal sliding. High‐order channels are associated with lake basins that exceed melt water storage capacity. Evolution of channel networks is coupled to changes in melt water production, runoff, and ice dynamics with implication for the englacial and subglacial environments. © 2013 The Authors. Hydrological Processes Published by John Wiley & Sons, Ltd.