The distribution of macrozoobenthos in the southern North Sea in relation to meso-scale bedforms     

Martin J. Baptist  Jan van Dalfsen  Anke Weber  Sandra Passchier  Sytze van Heteren 《Estuarine, Coastal and Shelf Science》2006,68(3-4):538

This study investigates the distribution of macrozoobenthos in relation to meso-scale bedforms in the southern North Sea. Three sites on the Dutch Continental Shelf were sampled that are representative of large areas of the North Sea and show diverse morphological settings. These sites are (i) part of a shoreface-connected ridge, (ii) the lower part of a concave shoreface and (iii) a sandwave area. Within these sites, two or three different morphological units were distinguished. Sampling was undertaken in two seasons for two consecutive years. The species composition was analysed for differences in benthic assemblage within sites, based on the meso-scale morphology, and between sites and seasons. In addition, the benthic assemblage was correlated to water depth, median grain size (D50) and sorting (D60/D10). Results show that significant differences in the benthic assemblage can be found related to meso-scale bedforms, but macro-scale morphological setting and seasonal effects are more important.  相似文献   

A new ambiguity acceptance test threshold determination method with controllable failure rate   总被引：2，自引：1，他引：1  

Lei Wang  Sandra Verhagen 《Journal of Geodesy》2015,89(4):361-375

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Early Miocene Antarctic glacial history: new insights from heavy mineral analysis from ANDRILL AND-2A drill core sediments     

Francesco Iacoviello  Giovanna Giorgetti  Isabella Turbanti Memmi  Sandra Passchier 《International Journal of Earth Sciences》2015,104(3):853-872

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Characterization of volume change and strength behavior of micro-silica and lime-stabilized Cyprus clay     

GhavamShirazi  Sandra  Bilsel  Huriye 《Acta Geotechnica》2021,16(3):827-840

Acta Geotechnica - This study aims to assess the suitability of micro-silica (MS) as an industrial waste to modify the hydro-mechanical behavior of expansive soil in comparison with the use of lime...  相似文献   

Sustainability of deep-sea fisheries   总被引：1，自引：0，他引：1  

Elliott A. Norse  Sandra BrookeWilliam W.L. Cheung  Malcolm R. ClarkIvar Ekeland  Rainer FroeseKristina M. Gjerde  Richard L. HaedrichSelina S. Heppell  Telmo Morato  Lance E. MorganDaniel Pauly  Rashid SumailaReg Watson 《Marine Policy》2012,36(2):307-320

As coastal fisheries around the world have collapsed, industrial fishing has spread seaward and deeper in pursuit of the last economically attractive concentrations of fishable biomass. For a seafood-hungry world depending on the oceans' ecosystem services, it is crucial to know whether deep-sea fisheries can be sustainable.The deep sea is by far the largest but least productive part of the oceans, although in very limited places fish biomass can be very high. Most deep-sea fishes have life histories giving them far less population resilience/productivity than shallow-water fishes, and could be fished sustainably only at very low catch rates if population resilience were the sole consideration. But like old-growth trees and great whales, their biomass makes them tempting targets while their low productivity creates strong economic incentive to liquidate their populations rather than exploiting them sustainably (Clark's Law). Many deep-sea fisheries use bottom trawls, which often have high impacts on nontarget fishes (e.g., sharks) and invertebrates (e.g., corals), and can often proceed only because they receive massive government subsidies. The combination of very low target population productivity, nonselective fishing gear, economics that favor population liquidation and a very weak regulatory regime makes deep-sea fisheries unsustainable with very few exceptions. Rather, deep-sea fisheries more closely resemble mining operations that serially eliminate fishable populations and move on.Instead of mining fish from the least-suitable places on Earth, an ecologically and economically preferable strategy would be rebuilding and sustainably fishing resilient populations in the most suitable places, namely shallower and more productive marine ecosystems that are closer to markets.  相似文献   

A pseudo-genetic stochastic model to generate karstic networks     

Andrea Borghi  Philippe Renard  Sandra Jenni 《Journal of Hydrology》2012

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Analytical Solution for Modeling Discharge into a Tunnel Drilled in a Heterogeneous Unconfined Aquifer     

Jean‐Christophe Maréchal  Sandra Lanini  Bertrand Aunay  Pierre Perrochet 《Ground water》2014,52(4):597-605

Predicting transient inflow rates into a tunnel is an important issue faced by hydrogeologists. Most existing analytical solutions overestimate the initial discharge due to the assumption that drilling was instantaneous over the entire tunnel length. In addition, they assume a homogeneous system. An alternative model was recently developed for tunnels intersecting heterogeneous formations, but its application was reduced to the case of confined flow to deep tunnels in weakly diffusive aquifers. In this paper, we adapt existing analytical solutions for drainage systems to the specific case of a tunnel progressively drilled in a highly diffusive heterogeneous unconfined aquifer. The case of a tunnel overlying an impervious layer is analytically solved by applying the superposition principle, while the case of a tunnel constructed some distance above an impervious layer is solved by discretizing the tunnel length into subsectors. Both models can simulate transient discharge into a tunnel drilled at various speeds through a heterogeneous unconfined aquifer, and allow the prediction of discharge rates in shallow tunnels located in highly diffusive aquifers. We successfully applied this approach to a tunnel in heterogeneous volcanic rock.  相似文献   

Slope‐area thresholds of road‐induced gully erosion and consequent hillslope–channel interactions          下载免费PDF全文

Harry Alexander Katz  J. Michael Daniels  Sandra Ryan 《地球表面变化过程与地形》2014,39(3):285-295

Pikes Peak Highway is a partially paved road between Cascade, Colorado and the summit of Pikes Peak. Significant gully erosion is occurring on the hillslopes due to the concentration of surface runoff, the rearrangement of drainage pathways along the road surface and adjacent drainage ditches, and the high erodibility of weathered Pikes Peak granite that underlies the area. As a result, large quantities of sediment are transported to surrounding valley networks causing significant damage to water quality and aquatic, wetland, and riparian ecosystems. This study establishes the slope/drainage area threshold for gullying along Pikes Peak Highway and a cesium‐137 based sediment budget highlighting rates of gully erosion and subsequent valley deposition for a small headwater basin. The threshold for gullying along the road is S_cr = 0 · 21A^–0·45 and the road surface reduces the critical slope requirement for gullying compared to natural drainages in the area. Total gully volume for the 20 gullies along the road is estimated at 5974 m³, with an erosion rate of 64 m³ yr^–1 to 101 m³ yr^–1. Net valley deposition is estimated at 162 m³ yr^–1 with 120 m³ yr^–1 unaccounted for by gullying. The hillslope–channel interface is decoupled with minimal downstream sediment transport which results in significant local gully‐derived sedimentation. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Evaluation of energy balance closure adjustment methods by independent evapotranspiration estimates from lysimeters and hydrological simulations          下载免费PDF全文

Matthias Mauder  Sandra Genzel  Jin Fu  Ralf Kiese  Mohsen Soltani  Rainer Steinbrecher  Matthias Zeeman  Tirtha Banerjee  Frederik De Roo  Harald Kunstmann 《水文研究》2018,32(1):39-50

Non‐closure of the surface energy balance is a frequently observed phenomenon of hydrometeorological field measurements, when using the eddy‐covariance method, which can be ascribed to an underestimation of the turbulent fluxes. Several approaches have been proposed in order to adjust the measured fluxes for this apparent systematic error. However, there are uncertainties about partitioning of the energy balance residual between the sensible and latent heat flux and whether such a correction should be applied on 30‐min data or longer time scales. The data for this study originate from two grassland sites in southern Germany, where measurements from weighable lysimeters are available as reference. The adjusted evapotranspiration rates are also compared with joint energy and water balance simulations using a physically based distributed hydrological model. We evaluate two adjustment methods: the first one preserves the Bowen ratio and the correction factor is determined on a daily basis. The second one attributes a smaller portion of the residual energy to the latent heat flux than to the sensible heat flux for closing the energy balance for every 30‐min flux integration interval. Both methods lead to an improved agreement of the eddy‐covariance based fluxes with the independent lysimeter estimates and the physically based model simulations. The first method results in a better comparability of evapotranspiration rates, and the second method leads to a smaller overall bias. These results are similar between both sites despite considerable differences in terrain complexity and grassland management. Moreover, we found that a daily adjustment factor leads to less scatter than a complete partitioning of the residual for every half‐hour time interval. The vertical temperature gradient in the surface layer and friction velocity were identified as important predictors for a potential future parameterisation of the energy balance residual.  相似文献   

DNA barcode,taxonomic and ecological notes for the identification of the invasive amphipod Monocorophium acherusicum (Costa, 1851)     

Mariano J. Albano  Carlos Rumbold  Ignacio L. Chiesa  Guadalupe Vazquez  Eduardo D. Spivak  Sandra M. Obenat 《新西兰海洋与淡水研究杂志》2019,53(1):15-32

We report the occurrence of the invasive amphipod Monocorophium acherusicum in Mar del Plata port, Argentina, using morphological and molecular analysis and estimated mean abundance to detect monthly variations of this population. We compared M. acherusicum morphology with that of M. insidiosum and Crassicorophium bonelli, the two most similar locally occurring species, to establish the diagnostic characteristics for the correct identification of them; moreover, we provide some taxonomic notes about others corophiids regionally distributed. M. acherusicum were collected in a subtidal biofouling community and its mean abundance was maximum in summer. In the molecular analysis, the maximum-likelihood tree showed that specimens from Mar del Plata were clustered with M. acherusicum specimens from GenBank and Boldsystems. We support and confirm the species identity in Mar del Plata port using DNA barcoding and with taxonomic methods.  相似文献