The ecological implications of a Yakutian mammoth's last meal   总被引：1，自引：0，他引：1  

Bas van Geel  Andr Aptroot  Claudia Baittinger  Hilary H. Birks  Ian D. Bull  Hugh B. Cross  Richard P. Evershed  Barbara Gravendeel  Erwin J.O. Kompanje  Peter Kuperus  Dick Mol  Klaas G.J. Nierop  Jan Peter Pals  Alexei N. Tikhonov  Guido van Reenen  Peter H. van Tienderen 《Quaternary Research》2008,69(3):361-376

Part of a large male woolly mammoth (Mammuthus primigenius) was preserved in permafrost in northern Yakutia. It was radiocarbon dated to ca. 18,500 ¹⁴C yr BP (ca. 22,500 cal yr BP). Dung from the lower intestine was subjected to a multiproxy array of microscopic, chemical, and molecular techniques to reconstruct the diet, the season of death, and the paleoenvironment. Pollen and plant macro-remains showed that grasses and sedges were the main food, with considerable amounts of dwarf willow twigs and a variety of herbs and mosses. Analyses of 110-bp fragments of the plastid rbcL gene amplified from DNA and of organic compounds supplemented the microscopic identifications. Fruit-bodies of dung-inhabiting Ascomycete fungi which develop after at least one week of exposure to air were found inside the intestine. Therefore the mammoth had eaten dung. It was probably mammoth dung as no bile acids were detected among the fecal biomarkers analysed. The plant assemblage and the presence of the first spring vessels of terminal tree-rings of dwarf willows indicated that the animal died in early spring. The mammoth lived in extensive cold treeless grassland vegetation interspersed with wetter, more productive meadows. The study demonstrated the paleoecological potential of several biochemical analytical techniques.  相似文献   

Combination of multi-mission altimetry data along the Mekong River with spatio-temporal kriging     

Eva Boergens  Sven Buhl  Denise Dettmering  Claudia Klüppelberg  Florian Seitz 《Journal of Geodesy》2017,91(5):519-534

River water-level time series at fixed geographical locations, so-called virtual stations, have been computed from single altimeter crossings for many years. Their temporal resolution is limited by the repeat cycle of the individual altimetry missions. The combination of all altimetry measurements along a river enables computing a water-level time series with improved temporal and spatial resolutions. This study uses the geostatistical method of spatio-temporal ordinary kriging to link multi-mission altimetry data along the Mekong River. The required covariance models reflecting the water flow are estimated based on empirical covariance values between altimetry observations at various locations. In this study, two covariance models are developed and tested in the case of the Mekong River: a stationary and a non-stationary covariance model. The proposed approach predicts water-level time series at different locations along the Mekong River with a temporal resolution of 5 days. Validation is performed against in situ data from four gauging stations, yielding RMS differences between 0.82 and 1.29 m and squared correlation coefficients between 0.89 and 0.94. Both models produce comparable results when used for combining data from Envisat, Jason-1, and SARAL for the time period between 2002 and 2015. The quality of the predicted time series turns out to be robust against a possibly decreasing availability of altimetry mission data. This demonstrates that our method is able to close the data gap between the end of the Envisat and the launch of the SARAL mission with interpolated time series.  相似文献   

Prograde and retrograde fluid-rock interaction in calc-silicates northwest of the Idaho batholith: stable isotopic evidence     

Claudia I. Mora  John W. Valley 《Contributions to Mineralogy and Petrology》1991,108(1-2):162-174

Carbon and oxygen isotopic analyses of silicate and carbonate minerals indicate that isotopic compositions in metasediments of the Wallace Formation (Belt Supergroup) exposed northwest of the Idaho batholith have been affected by both prograde and retrograde fluid-rock interaction. Silicates retain isotopic fractionations that reflect equilibration at peak metamorphic temperatures. In contrast, calcite oxygen isotopic compositions range from δ¹⁸O(Calcite)=+2.3 to +18.6‰ SMOW (standard mean oceanic water) and indicate that some calcites have exchanged with low-δ¹⁸O meteorichydrothermal fluids. Values of Δ¹⁸O (Quartz-Calcite) as large as +15.5 clearly indicate that the isotopic depletion of these calcites postdates the peak of regional metamorphism. Carbon isotopic compositions of ¹⁸O-depleted calcites are not significantly shifted relative to δ¹³C values in undepleted calcites, suggesting that the retrograde fluid was carbon-poor. Petrographically, retrograde fluid-rock interaction is associated with the occurrence of fine-grained, highly-luminescent calcite overgrowths on less-luminescent, metamorphic calcites, slight to moderate argillic alteration, and pseudomorphing of scapolite porphyroblasts by fine-grained albite. Retrograde isotopic depletions may be related to shallow meteoric-hydrothermal fluid flow developed around the Idaho batholith after intrusion and rapid uplift of the terrane. Peak metamorphic isotopic compositions in the Wallace Formation reflect mineralogically heterogeneous protolith compositions and isotopic fractionation due to devolatilization and/or infiltration. Variability in oxygen isotopic compositions on the order of 4–6‰ within the same rock type can be attributed to the combined effects of inherited isotopic compositions and isotopic shifts resulting from prograde devolatilization. Isotopic and compositional heterogeneity on the scale of mm to m precludes generalization of isotopic gradients on a regional scale. The isotopic data presented here, and metamorphic fluid compositions determined in previous studies, are best reconciled with heterogeneous bulk compositions, dominantly channelized prograde and retrograde fluid flow, and locally low fluid-rock ratios.  相似文献   

Social–ecological challenges in the Yellow River basin (China): a review     

Christian Wohlfart  Claudia Kuenzer  Cui Chen  Gaohuan Liu 《Environmental Earth Sciences》2016,75(13):1066

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Scraping and extirpating: two strategies to induce recovery of diseased Gorgonia ventalina sea fans          下载免费PDF全文

Claudia Patricia Ruiz‐Diaz  Carlos Toledo‐Hernández  Alex E. Mercado‐Molina  Alberto M. Sabat 《Marine Ecology》2016,37(2):336-343

Coral diseases are currently playing a major role in the worldwide decline in coral reef integrity. One of the coral species most afflicted by disease in the Caribbean, and which has been the focus of much research, is the sea fan Gorgonia ventalina. There is, however, very little information regarding the capacity of sea fans to recover after being infected. The aim of this study was to compare the rehabilitation capacity of G. ventalina after diseased‐induced lesions were eliminated either by scraping or extirpating the affected area. Scraping consisted of removing any organisms overgrowing the axial skeleton from the diseased area as well as the purple tissue bordering these overgrowths using metal bristle brushes. Extirpation consisted of cutting the diseased area, including the surrounding purpled tissue, using scissors. The number of scraped colonies that fully or partially rehabilitated after being manipulated and the rates at which the sea fans whose lesions were scrapped grew back healthy tissue were compared among: (i) colonies that inhabited two sites with contrasting environmental conditions; (ii) colonies of different sizes and (iii) colonies with different ratios of area of legions to total colony area (LA/CA). Both strategies proved to be very successful in eliminating lesions from sea fans. In the case of scraping, over 51% of the colonies recovered between 80% and 100% of the lost tissue within 16 months. The number of colonies that recovered from scraping was similar among sites and among colony sizes, but differed significantly depending on the relative amount of lesion to colony area (LA/CA). When lesions were extirpated, lesions did not reappear in any of the colonies. We conclude that lesion scraping is useful for eliminating relatively small lesions (i.e. LA/CA < 10%), as these are likely to recover in a shorter period of time, whereas for relatively large lesions (LA/CA ≥ 10%) it is more appropriate to extirpate the lesion.  相似文献   

Mt. Etna volcano high-resolution topography: airborne LiDAR modelling validated by GPS data     

Marina Bisson  Claudia Spinetti  Marco Neri  Alessandro Bonforte 《International Journal of Digital Earth》2016,9(7):710-732

High-resolution digital topography is essential for land management and planning in any type of territory as well as the reproduction of the Earth surface in a geocoded digital format that allows several Digital Earth applications. In a volcanic environment, Digital Elevation Models are a valid reference for multi-temporal analyses aimed to observe frequent changes of a volcano edifice and for the relative detailed morphological and structural analyses. For the first time, a DTM (Digital Terrain Model) and a DSM (Digital Surface Model) covering the entire Mt. Etna volcano (Italy) derived from the same airborne Light Detection and Ranging (LiDAR) are here presented. More than 250 million 3D LiDAR points have been processed to distinguish ground elements from natural and anthropic features. The end product is the highly accurate representation of Mt. Etna landscape (DSM) and ground topography (DTM) dated 2005. Both models have a high spatial resolution of 2?m and cover an area of 620?km². The DTM has been validated by GPS ground control points. The vertical accuracy has been evaluated, resulting in a root-mean-square-error of ±?0.24?m. The DTM is available as electronic supplement and represents a valid support for various scientific studies.  相似文献   

Water availability and land subsidence in the Central Valley,California, USA     

Claudia C. Faunt  Michelle Sneed  Jon Traum  Justin T. Brandt 《Hydrogeology Journal》2016,24(3):675-684

The Central Valley in California (USA) covers about 52,000 km² and is one of the most productive agricultural regions in the world. This agriculture relies heavily on surface-water diversions and groundwater pumpage to meet irrigation water demand. Because the valley is semi-arid and surface-water availability varies substantially, agriculture relies heavily on local groundwater. In the southern two thirds of the valley, the San Joaquin Valley, historic and recent groundwater pumpage has caused significant and extensive drawdowns, aquifer-system compaction and subsidence. During recent drought periods (2007–2009 and 2012-present), groundwater pumping has increased owing to a combination of decreased surface-water availability and land-use changes. Declining groundwater levels, approaching or surpassing historical low levels, have caused accelerated and renewed compaction and subsidence that likely is mostly permanent. The subsidence has caused operational, maintenance, and construction-design problems for water-delivery and flood-control canals in the San Joaquin Valley. Planning for the effects of continued subsidence in the area is important for water agencies. As land use, managed aquifer recharge, and surface-water availability continue to vary, long-term groundwater-level and subsidence monitoring and modelling are critical to understanding the dynamics of historical and continued groundwater use resulting in additional water-level and groundwater storage declines, and associated subsidence. Modeling tools such as the Central Valley Hydrologic Model, can be used in the evaluation of management strategies to mitigate adverse impacts due to subsidence while also optimizing water availability. This knowledge will be critical for successful implementation of recent legislation aimed toward sustainable groundwater use.  相似文献   

The balance between microzooplankton grazing and phytoplankton growth in a highly productive estuarine fjord   总被引：1，自引：4，他引：1  

Andrew W. Leising  Rita Horner  James J. Pierson  James Postel  Claudia Halsband-Lenk 《Progress in Oceanography》2005,67(3-4):366

During 24, three-day cruises to Dabob Bay, Washington State, USA, from February 4 to April 26, 2002, and February 4 to May 1 2003, we examined the relative growth and grazing rates of phytoplankton and microzooplankton using dilution experiments. Experiments were conducted over two time intervals: 8–10 h during the nighttime only, or 24 h from noon to noon. We used water from two depths during each cruise: from the surface mixed layer, and from a deep layer below the seasonal thermocline. During 2002, there was one mid-sized bloom consisting mainly of Thalassiosira spp. in early February, and a larger bloom in April comprised of two Chaetoceros spp. and Phaeocystis sp. During 2003, there were also two blooms, one in early February, which was again dominated by Thalassiosira spp., and a second larger bloom in mid-April, comprised mainly of Thalassiosira spp. and Chaetoceros spp. During all four of these blooms, and for both water source depths, specific grazing rates of microzooplankton were most often as high or higher than the calculated phytoplankton specific growth rates. The major microzooplankton categories that could have accounted for this were (1) a large Gyrodinium spp., (2) a group of fusiform-shaped mid-sized Protoperidinium species, and (3) three loosely defined taxonomic groups consisting of naked ciliates, tintinnids, and unidentified heterotrophic dinoflagellates. Based on our measurements, it appears that the microzooplankton community grazing pressure can often exert significant control on phytoplankton biomass, even during the extremely productive spring bloom periods and under several different diatom-dominated bloom types. These results suggest that even in highly productive estuarine ecosystems, which are often nurseries to economically important fisheries species, microzooplankton play a critical role and may significantly alter the availability and efficiency of transfer of energy to higher trophic levels.  相似文献   

Refining P nuclear magnetic resonance spectroscopy for marine particulate samples: Storage conditions and extraction recovery     

Barbara J. Cade-Menun  Claudia R. Benitez-Nelson  Perry Pellechia  Adina Paytan 《Marine Chemistry》2005,97(3-4):293-306

Solution ³¹P nuclear magnetic resonance (NMR) spectroscopy has recently been used to characterize phosphorus species within marine particles. However, the effects of sample collection, storage and preparation have not been thoroughly examined. In this study, samples of settling particulates collected from a 1200-m sediment trap located in Monterey Bay, California, were subjected to various storage options (i.e., no storage, refrigeration, freezing, and oven-drying and grinding) prior to extraction for solution ³¹P-NMR spectroscopy. Freezing, refrigerating and drying samples for periods of up to 6 months prior to extraction with 0.25 M NaOH + 0.05 M Na₂EDTA increased the concentration of extracted P by an average of 16% relative to samples extracted without storage. Pre-extraction storage also introduced some minor changes in P speciation, by increasing the percentage of orthophosphate by up to 15% and decreasing the percentage of pyrophosphate by up to 5%, relative to the abundances of these P species in samples extracted without storage. Drying caused the biggest changes in speciation, specifically decreasing more extensively the relative percentage of pyrophosphate compared to other treatments. Nevertheless, observed changes in speciation due to sample storage within a specific sample were small relative to differences observed among samples collected sequentially in the same area, or reported differences among samples collected at different locations. Samples were also analyzed by solid-state ³¹P-NMR spectroscopy before and after extraction, to examine extraction-related changes in P speciation. Comparison of solution with solid-state ³¹P NMR indicates that extraction with NaOH–EDTA removes the majority of organic esters, but only a variable portion of phosphonates (39–67%). In addition, there was preferential extraction of Ca-associated phosphate over Mg-, Fe- and Al-associated phosphate. Solution ³¹P NMR enables much higher resolution of P species within samples, particularly when it is important to speciate orthophosphate monoesters and diesters, or if polyphosphates are present. However, combining solid-state ³¹P NMR with solution ³¹P NMR spectroscopy for marine particles should be conducted when examining inorganic P speciation and the abundance of phosphonates.  相似文献   

Life-history strategies of calanoid congeners under two different climate regimes: a comparison   总被引：5，自引：0，他引：5  

Halsband-Lenk  Claudia; Carlotti  Francois; Greve  Wulf 《ICES Journal of Marine Science》2004,61(4):709-720

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