Dynamics and sources of suspended particulate organic matter in the Marennes-Oléron oyster farming bay: Insights from stable isotopes and microalgae ecology     

Nathalie Malet  Pierre-Guy Sauriau  Mireille Ryckaert  Pascale Malestroit  Gael Guillou 《Estuarine, Coastal and Shelf Science》2008

The aim of this study was to distinguish between sources of the complex variety of Marennes-Oléron Bay suspended particulate organic matter (SPOM) contributing to the tropho-dynamics of the Marennes-Oléron oyster farming bay. Basic biomarkers (Chl a, C/N and POC/Chl a ratios), carbon and nitrogen stable isotopes from SPOM were analyzed and the microalgae community was characterized. The sampling strategy was bimonthly from March 2002 to December 2003; samples were taken from an intertidal mudflat. Four main sources contributed to the SPOM pool: terrigenous input from rivers, neritic phytoplankton, resuspended microphytobenthos and periodic inputs from intertidal Zostera noltii meadows. Seasonal fluctuations were observed in both years of the study period: (1) SPOM collected in the spring of 2002 (δ¹³C = −25‰ to −23‰) was mainly composed of fresh estuarine inputs; (2) SPOM from the summer and fall of 2002 and 2003 was predominantly neritic phytoplankton (δ¹³C = − 22‰ to −19‰); (3) SPOM from the winter of 2002, spring of 2003 and winter of 2003 (δ¹³C = −21 to −23‰) was composed of a mixture of decayed terrigenous river inputs and pelagic phytoplankton, which was predominantly resuspended microphytobenthos. In the summer of 2003—the warmest summer on record in southern France and Europe—SPOM was particularly enriched for ¹³C, with δ¹³C values ranging from −14‰ to −12‰. Pulses in δ¹³C values, indicative of ¹³C-enriched decaying materials, extended into the fall. These were attributed to benthic intertidal inputs, including both resuspended microphytobenthos and Z. noltii detritus. Changes in SPOM sources in Marennes-Oléron Bay may lead to differences in the quality of the trophic environment available for reared oysters.  相似文献   

No Development,No Conservation: Elements from the Conservation of Farm Animal Genetic Resources     

Anne Lauvie  Nathalie Couix  Etienne Verrier 《社会与自然资源》2014,27(12):1331-1338

Using concrete examples of conservation of farm animal genetic resources, we show that conservation and development should not be considered as two opposing processes. On the contrary, their synergies can facilitate conservation dynamics. We discuss conservation and development dynamics, and provide examples of synergies between the two dynamics to underline how development dynamics can help conservation programs.  相似文献   

Changes in sub-fossil chironomid assemblages in two Northern Patagonian lake systems associated with the occurrence of historical fires     

Alberto Araneda  Patricia Jana  Carolina Ortega  Fernando Torrejón  Sébastien Bertrand  Patricia Vargas  Nathalie Fagel  Denisse Alvarez  Alejandra Stehr  Roberto Urrutia 《Journal of Paleolimnology》2013,50(1):41-56

Patagonia is commonly seen as an exceptionally pristine area because of its wildlife and practically unpolluted waters. However, during the twentieth century the burning of natural forests was one of the most important human activities in Northern Chilean Patagonia. Some estimations indicate that three million hectares were burned during the first three decades of the century. Hence the objective of this study was to evaluate the impacts of the historical fires in Lake Burgos (45º42′S) and Lake Thompson (45º38′S) in Chilean Patagonia. The impact was measured by evaluating chironomid assemblage since they are sensitive enough to be used as an indicator of aquatic ecosystem health. Fires have a direct and drastic effect on a lake watershed but also indirectly affect a lake ecosystem, changing sedimentation patterns or increasing nutrient inputs. In the studied lakes the periods with higher prevalence of fires were identified by charcoal analysis, while organic matter and magnetic susceptibility allowed the confirmation of pre-fire and post-fire periods. The chironomid composition was evaluated through a PCA and an analysis of similarity (ANOSIM) to test the significance among periods while a Detrended Correspondence Analysis was applied to the chironomid assemblage downcore to assess compositional structure and taxa turnover. In Lake Burgos the ANOSIM test indicated significant differences between the pre-fire and fire periods (p < 0.05), while in Lake Thompson differences were not significant. However, in Lake Thompson the PCA clearly separated the pre-fire from the fire period but not the fire from the post-fire periods. In both lakes chironomid composition changed in relation to the period of higher prevalence of fires, which in turn implies catchment changes, pollution, and other anthropogenic impacts. Particularly a marked change in mesotrophic/eutrophic taxa was detected, reflecting an increase in nutrient input due to deforestation. Our findings point out that the lacustrine ecosystems are still affected by the impact of fires and the subsequent increase in nutrient supply that occurred almost 50 years ago. No sign of reverting to pre-disturbance conditions was observed, which makes these lakes highly sensitive to current human-induced impacts.  相似文献   

Large-Scale Mapping of Hard-Rock Aquifer Properties Applied to Burkina Faso     

Nathalie Courtois  Patrick Lachassagne  Robert Wyns  Raymonde Blanchin  Francis D. Bougaïré  Sylvain Somé  Aïssata Tapsoba 《Ground water》2010,48(2):269-283

A country-scale (1:1,000,000) methodology has been developed for hydrogeologic mapping of hard-rock aquifers (granitic and metamorphic rocks) of the type that underlie a large part of the African continent. The method is based on quantifying the “useful thickness” and hydrodynamic properties of such aquifers and uses a recent conceptual model developed for this hydrogeologic context. This model links hydrodynamic parameters (transmissivity, storativity) to lithology and the geometry of the various layers constituting a weathering profile. The country-scale hydrogeological mapping was implemented in Burkina Faso, where a recent 1:1,000,000-scale digital geological map and a database of some 16,000 water wells were used to evaluate the methodology.  相似文献   

Timing of the late glacial and Younger Dryas cold reversal in southern Chile varved sediments     

Xavier Boës  Nathalie Fagel 《Journal of Paleolimnology》2008,39(2):267-281

The timing of the last deglaciation in southern Chile is re-evaluated from a calendar varve chronology (Lago Puyehue, 40° S). The climate shifts are analysed by continuous annual varve-thickness measurements through the ∼17,100 cal. year to 10,800 cal. year BP time window (∼3.5 m sediment core). The varve years are determined by the alternation of light (phytoplankton-rich) and dark (terrigenous and organic-rich) layers forming graded annual couplets (∼0.2 to 0.8 mm/year). The varve chronology is constructed by conventional varve-counting methods on thin sections after correction for instantaneous volcanic and/or seismic events detected in the thin sections. The calibrated varve-age model derived from the manual varve counting is constrained by high-resolution grey-scale (GS) semi-automatic counts of the annual light phytoplankton-rich layers (∼120 μm to 300 μm thick). Due to physical sediment properties the GS constitutes a proxy record for the phytoplankton/terrigenous varve-thickness variations through the sediment record. The varve couplets are thicker/thinner during humid/dry phases and darker/lighter (negative/positive annual grey-scale index) during cold/warm phases. Our results show that at 40° S the last deglaciation took place in two phases between ∼17,100 cal. year and ∼15,500 cal. year BP. We note a climate instability between ∼15,500 cal. year and 13,300 cal. year BP and a significant dry phase between ∼15,000 and 14,500 cal. year BP. We evidence a cold event in two phases between ∼13,300 and 12,200 cal. year BP interrupted by a dry event between ∼12,800 and 12,600 cal. year BP. The onset of a significant warmer period is observed after ∼11,500 cal. year BP. Our results provide new evidence of a Younger Dryas cool reversal in southern Chile, i.e., the Huelmo/Mascardi event Hajdas et al. (2003) associated with an abrupt dry pulse at ∼12,800–12,600 cal. year BP. The high-resolution grey-scale measurements performed on the biogenic varves from Lago Puyehue provide a reliable calibrated chronology of the regional environmental and climate shifts during the last deglaciation. This is eighth in a series of eight papers published in this special issue dedicated to the 17,900 year multi-proxy lacustrine record of Lago Puyehue, Chilean Lake District. The papers in this issue were collected by M. De Batist, N. Fagel, M.-F. Loutre and E. Chapron.  相似文献   

Components of rainy seasons’ variability in Equatorial East Africa: onset, cessation, rainfall frequency and intensity   总被引：1，自引：0，他引：1  

Pierre Camberlin  Vincent Moron  Raphael Okoola  Nathalie Philippon  Wilson Gitau 《Theoretical and Applied Climatology》2009,98(3-4):237-249

  相似文献   

Climate change impacts on water management and irrigated agriculture in the Yakima River Basin, Washington, USA   总被引：1，自引：0，他引：1  

Julie A. Vano  Michael J. Scott  Nathalie Voisin  Claudio O. Stöckle  Alan F. Hamlet  Kristian E. B. Mickelson  Marketa McGuire Elsner  Dennis P. Lettenmaier 《Climatic change》2010,102(1-2):287-317

The Yakima River Reservoir system supplies water to ~180,000 irrigated hectares through the operation of five reservoirs with cumulative storage of ~30% mean annual river flow. Runoff is derived mostly from winter precipitation in the Cascade Mountains, much of which is stored as snowpack. Climate change is expected to result in earlier snowmelt runoff and reduced summer flows. Effects of these changes on irrigated agriculture were simulated using a reservoir system model coupled to a hydrological model driven by downscaled scenarios from 20 climate models archived by the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. We find earlier snowmelt results in increased water delivery curtailments. Historically, the basin experienced substantial water shortages in 14% of years. Without adaptations, for IPCC A1B global emission scenarios, water shortages increase to 27% (13% to 49% range) in the 2020s, to 33% in the 2040s, and 68% in the 2080s. For IPCC B1 emissions scenarios, shortages occur in 24% (7% to 54%) of years in the 2020s, 31% in the 2040s and 43% in the 2080s. Historically unprecedented conditions where senior water rights holders suffer shortfalls occur with increasing frequency in both A1B and B1 scenarios. Economic losses include expected annual production declines of 5%–16%, with greater probabilities of operating losses for junior water rights holders.  相似文献   

Quantifying historic skew surges: an example for the Dunkirk Area,France     

Giloy  Nathalie  Hamdi  Yasser  Bardet  Lise  Garnier  Emmanuel  Duluc  Claire-Maire 《Natural Hazards》2019,98(3):869-893

Natural Hazards - As instrumental records often cover only short time periods, historical information is the main source of data in order to extend natural disaster catalogs. This study...  相似文献   

Mobility and exile at 2nd century A.D. khirbet edh‐dharih: Strontium isotope analysis of human migration in western Jordan     

Megan A. Perry  Drew Coleman  Nathalie Delhopital 《Geoarchaeology》2008,23(4):528-549

The 2nd century A.D. Roman annexation of the Nabataean Kingdom may have resulted in significant settlement disruption. Here we investigate the possibility that political refugees occupied Khirbet edh‐Dharih after Roman takeover, using strontium isotope analysis of archaeological human dental enamel. We additionally discuss regional patterning of 87Sr/86Sr in western Jordan based on archaeological faunal dental enamel samples to understand strontium isotope spatial heterogeneity and to facilitate interpretation of the Dharih results. Strontium isotope analysis of small mammal dentition varied as expected based on bedrock geology, but small faunal sample sizes did not accurately reflect the broad range of biologically available strontium at Dharih. Only one person at Khirbet edh‐Dharh appears to be non‐local based on isotopic data. The status of the remaining individuals is unclear, as they could have originated from Dharih or the Nabataean capital city of Petra. Incorporating modern fauna and soil samples to establish the local value may assist in characterizing the local strontium in a geologically complex area such as Dharih. Futhermore, future analysis of elemental strontium to assess dietary composition and diagenetic contamination would facilitate interpretation of the strontium sources in the Dharih individuals. © 2008 Wiley Periodicals, Inc.  相似文献   

Viscoelastic approximation of poroelastic media for wave scattering problems   总被引：1，自引：0，他引：1  

V. Morochnik  J.P. Bardet 《Soil Dynamics and Earthquake Engineering》1996,15(5):337-346

Herein, we propose a simplified and approximate method for solving dynamic problems in poroelastic media. The method is based on the definition of equivalent-viscoelastic materials that have the same wave numbers as poroelastic media. The viscoelastic approximation was applied to study the scatter of plane compressional waves by a spherical poroelastic inhomogeneity. In this wave scattering problem, the poroelastic and equivalent-viscoelastic solutions gave almost identical results far away from the inhomogeneity. The proposed method extends our existing numerical and analytical methods for poroelastic media. It is useful to derive approximate analytical solutions which can be applied for assessing the damping characteristics of small amplitude waves in saturated soils.  相似文献