Deep-sea macrourid fishes scavenge on plant material: Evidence from in situ observations     

Rachel M. Jeffreys  Marc S.S. Lavaleye  Magda J.N. Bergman  Gerard C.A. Duineveld  Rob Witbaard  Thom Linley 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(4):621-627

Deep-sea benthic communities primarily rely on an allochthonous food source. This may be in the form of phytodetritus or as food falls e.g. sinking carcasses of nekton or debris of marine macrophyte algae. Deep-sea macrourids are the most abundant demersal fish in the deep ocean. Macrourids are generally considered to be the apex predators/scavengers in deep-sea communities. Baited camera experiments and stable isotope analyses have demonstrated that animal carrion derived from the surface waters is an important component in the diets of macrourids; some macrourid stomachs also contained vegetable/plant material e.g. onion peels, oranges, algae. The latter observations led us to the question: is plant material an attractive food source for deep-sea scavenging fish? We simulated a plant food fall using in situ benthic lander systems equipped with a baited time-lapse camera. Abyssal macrourids and cusk-eels were attracted to the bait, both feeding vigorously on the bait, and the majority of the bait was consumed in <30 h. These observations indicate (1) plant material can produce an odour plume similar to that of animal carrion and attracts deep-sea fish, and (2) deep-sea fish readily eat plant material. This represents to our knowledge the first in situ documentation of deep-sea fish ingesting plant material and highlights the variability in the scavenging nature of deep-sea fishes. This may have implications for food webs in areas where macrophyte/seagrass detritus is abundant at the seafloor e.g. canyon systems and continental shelves close to seagrass meadows (Bahamas and Mediterranean).  相似文献   

Readily dispersible clay and its role in the mobility of transition metals Cd2+, Cu2+ and Zn2+ in an alkaline alluvial soil     

Mohamed Rashad  Essam Elnaggar  Faiz F. Assaad 《Environmental Earth Sciences》2014,71(9):3855-3864

Readily dispersible clay is the part of the clay fraction in soils that potentially disperses in water when a small amount of mechanical energy is applied to soil. Column and batch experiments were conducted to identify the effect of readily dispersible clay on the mobility of some metal ions in a disturbed soil sample. The clay fraction (<0.002 mm) was separated from an alkaline Vertisol from the Nile River Delta. X-ray diffraction technique was used to identify minerals present in the clay fraction. Clay suspensions and deionized H₂O solutions of Cd²⁺, Cu²⁺, and Zn²⁺ were prepared and used as influents in soil columns. Adsorption capability of the studied soil among the three metal ions was investigated. The results showed high adsorption capacity of Cd²⁺, Cu²⁺, but not Zn²⁺ for the studied soil. Cu²⁺ was the highest adsorbed metal by soil and its sorption increased at small equilibrium concentrations compared with Cd²⁺ and Zn²⁺. For the three studied metal ions, Langmuir model represented the best fit to the adsorption data. The concentration of Zn²⁺ and Cd²⁺ in leachates increased as the leaching solution volume increased, while Cu²⁺ showed a homogeneous distribution throughout the soil column. According to DTPA extractable metals, Zn²⁺ was appeared at greater depths than Cd²⁺, while Cu²⁺ had homogeneous distribution through the soil column.  相似文献   

Changes in nematode communities at the long-term sand extraction site of the Kwintebank (southern bight of the north sea)     

Vanaverbeke J  Deprez T  Vincx M 《Marine pollution bulletin》2007,54(9):1351-1360

We investigated the long-term effects of sand extraction activities on the nematode communities from the Kwintebank. Although changes in nematode community composition cannot be completely uncoupled from natural processes, we suggest that the morphological changes in the sandbank and physical disturbance associated with the dredging activities indeed affected nematode community composition. Nematode diversity did not change since the start of the extraction activities but nematode community composition changed significantly. The SIMPER routine identified predatory nematodes to be important for the within group similarity at the start of the exploitation, while similarity in 1997 and 2001 was determined by the contribution of deposit feeding nematodes. In addition, long nematodes, vulnerable to physical disturbance became less important. These changes are attributed to long term changes in sediment characteristics in combination with additional short-term disturbances by the creation and filling of dredge furrows which are related to the extraction activities.  相似文献   

Marine biological valuation mapping of the Basque continental shelf (Bay of Biscay), within the context of marine spatial planning     

Marta Pascual  Angel Borja  Sarah Vanden Eede  Klaas Deneudt  Magda Vincx  Ibon Galparsoro  Irati Legorburu 《Estuarine, Coastal and Shelf Science》2011

  相似文献   

The Anisotropic Schwarzschild-Type Problem, Main Features     

Vasile Mioc  Ernesto Pérez-Chavela  Magda Stavinschi 《Celestial Mechanics and Dynamical Astronomy》2003,86(1):81-106

The two-body problem associated to an anisotropic Schwarzschild-type field is being tackled. Both the motion equations and the energy integral are regularized via McGehee-type transformations. The regular vector field exhibits nice symmetries that form a commutative group endowed with an idempotent structure. The physically fictitious flows on the collision and infinity manifolds, as well as the local flows in the neighbourhood of these manifolds, are fully described. Homothetic, spiral, and oscillatory orbits are pointed out. Some features of the global flow are depicted for all possible levels of energy. For the negative-energy case, few things have been done. The positive-energy global flow does not have zero-velocity curves; every orbit is of the type ejection – escape or capture – collision. In the zero-energy case, the collision and infinity manifolds have a very similar structure. The existence of eight trajectories that connect the equilibria on these manifolds is proved. The projectability of the zero-energy global flow completes the full understanding of the problem in this case.  相似文献   

What drives national adaptation? A global assessment   总被引：1，自引：1，他引：0  

Lea Berrang-Ford  James D. Ford  Alexandra Lesnikowski  Carolyn Poutiainen  Magda Barrera  S. Jody Heymann 《Climatic change》2014,124(1-2):441-450

That the climate is changing and societies will have to adapt is now unequivocal, with adaptation becoming a core focus of climate policy. Our understanding of the challenges, needs, and opportunities for climate change adaptation has advanced significantly in recent years yet remains limited. Research has identified and theorized key determinants of adaptive capacity and barriers to adaptation, and more recently begun to track adaptation in practice. Despite this, there is negligible research investigating whether and indeed if adaptive capacity is translating into actual adaptation action. Here we test whether theorized determinants of adaptive capacity are associated with adaptation policy outcomes at the national level for 117 nations. We show that institutional capacity, in particular measures of good governance, are the strongest predictors of national adaptation policy. Adaptation at the national level is limited in countries with poor governance, and in the absence of good governance other presumed determinants of adaptive capacity show limited effect on adaptation. Our results highlight the critical importance of institutional good governance as a prerequisite for national adaptation. Other elements of theorized adaptive capacity are unlikely to be sufficient, effective, or present at the national level where national institutions and governance are poor.  相似文献   

Imaging the Mariánské Lázně Fault (Czech Republic) by 3-D ground-penetrating radar and electric resistivity tomography     

Tomá? Fischer  Petra ?těpan?íková  Magda Karousová  Petr Tábo?ík  Christina Flechsig  Mahmoud Gaballah 《Studia Geophysica et Geodaetica》2012,56(4):1019-1036

Geodynamic activity in the area of West Bohemia is typified by the occurrence of earthquake swarms, Quaternary volcanism and high flux of mantle-derived CO₂. The highest swarm activity occurs beneath the eastern edge of the Cheb basin, which is delineated by the NW-SE trending morphologically pronounced Mariánské Lázn?? Fault (MLF) controlling the formation of the basin. The previous trenching survey across the MLF zone has identified several fault strands with possible Quaternary activity. In this paper we present the results of the geophysical survey focused to trace the faults signatures in geophysical sections and to build an image of near surface tectonics. The method of electric resistivity tomography (ERT) along two profiles parallel to the trench identified a strong resistivity contrast between the bodies of sandy gravels in the middle and conductive clayey sands to the west and weathered crystalline basement to the east. The 2-D ground penetration radar (GPR) sections show direct correlation of reflections with lithological boundaries identified in the trench. As expected, the GPR signal amplitudes increase with the resistivities found in the ERT sections. Two of the four faults identified in the trench are indicated in the resistivity and GPR sections. A 3-D GPR measurement has identified a spot of high amplitudes elongated parallel to the MLF trend, which coincides with the high resistivity body. To improve the signal-to-noise ratio of the time slices we stacked the GPR time slices within vertically homogeneous blocks. This provided a contrast image of the sand-gravel body including its boundaries in three dimensions. The detailed analysis of the 3-D GPR cube revealed additional fault that limits the highly reflective sands and appears to be offset by another younger fault. Our results suggest a complex fault pattern in the studied area, which deserves a further study.  相似文献   

Fluid geochemistry of the Mondragone hydrothermal systems (southern Italy): water and gas compositions vs. geostructural setting     

Cuoco  Emilio  Minissale  Angelo  Di Leo  Antonella “Magda”  Tamburrino  Stella  Iorio  Marina  Tedesco  Dario 《International Journal of Earth Sciences》2017,106(7):2429-2444

International Journal of Earth Sciences - The geochemistry of natural thermal fluids discharging in the Mondragone Plain has been investigated. Thermal spring emergences are located along the...  相似文献   

Location-allocation modeling for emergency evacuation planning with GIS and remote sensing: A case study of Northeast Bangladesh     

Mahfuzur Rahman  Ningsheng Chen  Md Monirul Islam  Ashraf Dewan  Hamid Reza Pourghasemi  Rana Muhammad Ali Washakh  Nirdesh Nepal  Shufeng Tian  Hamid Faiz  Mehtab Alam  Naveed Ahmed 《地学前缘(英文版)》2021,12(3):101095

This work developed models to identify optimal spatial distribution of emergency evacuation centers(EECs) such as schools, colleges, hospitals, and fire stations to improve flood emergency planning in the Sylhet region of northeastern Bangladesh.The use of location-allocation models(LAMs) for evacuation in regard to flood victims is essential to minimize disaster risk.In the first step, flood susceptibility maps were developed using machine learning models(MLMs), including: Levenberg–Marquardt back propagation(LM-BP) neural network and decision trees(DT) and multi-criteria decision making(MCDM) method.Performance of the MLMs and MCDM techniques were assessed considering the area under the receiver operating characteristic(AUROC) curve.Mathematical approaches in a geographic information system(GIS) for four well-known LAM problems affecting emergency rescue time are proposed: maximal covering location problem(MCLP), the maximize attendance(MA), p-median problem(PMP), and the location set covering problem(LSCP).The results showed that existing EECs were not optimally distributed, and that some areas were not adequately served by EECs(i.e., not all demand points could be reached within a 60-min travel time).We concluded that the proposed models can be used to improve planning of the distribution of EECs, and that application of the models could contribute to reducing human casualties, property losses, and improve emergency operation.  相似文献   

Resource availability and meiofauna in sediment of tropical seagrass beds: local versus global trends     

De Troch M  Van Gansbeke D  Vincx M 《Marine environmental research》2006,61(1):59-73

Characterisation of productivity-diversity relationships forms an essential step towards a better understanding of biodiversity. In terrestrial systems this is a topical subject and most studies reported a hump-shaped relationship. For marine systems, however, the number of studies dedicated to this is low despite the high interest in this productivity-diversity relationship. The present study reports on meiofauna density/diversity patterns in relation to resource availability as an indicator for the productivity of the ecosystem. Standardised meiofauna samples were collected in tropical seagrass beds from three localities (Kenya, Mexico, the Philippines) in order to contrast local patterns with a more global scale. Although these sites were physically comparable, a range of resource availabilities was found. These differences between localities were mainly due to different tidal regimes and related input of organic matter. At all sites a significant positive effect of resource increase on meiofauna densities was found. This positive effect was less clear for meiofauna diversity. Highest density and diversity levels were reported for the Kenyan site and this is probably linked to a high tidal range. Pooling all localities together resulted in a significant positive linear relationship between resource availability and meiofauna density/diversity. Caution should be taken when choosing resource indicators. Chlorophyll a concentrations, for example, resulted in a positive density-productivity relationship while organic carbon content, an indicator for more refractory material, showed a negative relationship. In all cases, no hump-shaped relationship could be found suggesting that each ecosystem and each group of organisms may show a particular productivity-diversity/density relationship.  相似文献