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11.
Spatio-temporal variation of feeding intensity and diet in the red shrimp Aristeus antennatus was studied at two locations around the island of Mallorca (Balearic Islands, Western Mediterraean) in August, September, and November 2003, and in February, April and June 2004 at depths between 550 and 750 m. The two areas, with different oceanographic conditions, were respectively located in the northwest (Sóller) and the south (Cabrera) of Mallorca. Off Sóller, feeding intensity of A. antennatus showed a significant increase from February to April and June 2004 in all the three size-classes studied (small shrimps: CL < 30 mm; medium: CL between 30 and 40 mm; large: CL ? 40 mm). Off Cabrera, the highest fullness was recorded in November 2003 among small and medium shrimp, while only large specimens showed patterns similar to that found off Sóller. Off Sóller, the diet of both small (CL < 34 mm) and large (CL ? 34 mm) A. antennatus was mainly influenced by season, with three dietary groups corresponding to August-September 2003, to November 2003/February 2004, and to hauls from April to June 2004. Off Cabrera, hauls (representing diets) were grouped by depth, never by season. The most remarkable seasonal shift in the diet of A. antennatus off Sóller was the increase of mesopelagic prey in April-June relative to other months. In all size categories there was an increase off Sóller in the energy intake of prey ingested from February to June 2004, an increase not found off Cabrera. Degree of digestion of mesopelagic prey indicated nocturnal feeding on mesopelagic fauna. These prey probably have a shallower depth distribution at night than found in our daylight sampling, and possible migratory movements among prey and A. antennatus at night would explain the lack of correlation between prey abundance in guts and in the environment found during daylight periods for most micronekton mesopelagic prey (euphausiids, myctophids and sergestids). Off Sóller, fullness and diet were significantly linked to temporal changes in water column productivity (e.g., Chl a readings, fluorescence) and to changes in the shrimp biology (lipid content of hepatopancreas, Gonado-somatic Index, GSI). Off Cabrera, we found a higher dependence of fullness and diet with T and S, both variables in turn related to depth. The increase of stomach fullness and dietary energy intake in pre-reproductive females from February to April-June 2004 found off Sóller, coupled with the consumption of mesopelagic prey, was parallel to a significant increase of the gonad weight (GSI, fecundity) in June. Most individuals attain gonad development in the period May-June, after two months of the peak of primary production at the surface. The strong link found between pelagic resources and reproductive processes in a deep-sea species such as the shrimp Aristeus antennatus, situated near the top of the trophic web, suggests a rapid energy flow via mesopelagic fauna between surface primary production and bathyal megabenthic communities at oligotrophic insular areas. In contrast to mainland areas off the Catalan coasts submitted to the influence of submarine canyons, around the island of Mallorca the empoverishment of benthos biomass may enhance consumption of micronektonic prey and a possible accumulation of pre-reproductive females of A. antennatus in areas (e.g., steep slopes and persistent frontal systems found off Sóller) with high zooplankton aggregations. 相似文献
12.
Aurélie Rivier Anne-Claire Bennis Grégory Pinon Vanesa Magar Markus Gross 《Ocean Dynamics》2016,66(10):1285-1299
Monopile foundations of offshore wind turbines modify the hydrodynamics and sediment transport at local and regional scales. The aim of this work is to assess these modifications and to parameterize them in a regional model. In the present study, this is achieved through a regional circulation model, coupled with a sediment transport module, using two approaches. One approach is to explicitly model the monopiles in the mesh as dry cells, and the other is to parameterize them by adding a drag force term to the momentum and turbulence equations. Idealised cases are run using hydrodynamical conditions and sediment grain sizes typical from the area located off Courseulles-sur-Mer (Normandy, France), where an offshore windfarm is under planning, to assess the capacity of the model to reproduce the effect of the monopile on the environment. Then, the model is applied to a real configuration on an area including the future offshore windfarm of Courseulles-sur-Mer. Four monopiles are represented in the model using both approaches, and modifications of the hydrodynamics and sediment transport are assessed over a tidal cycle. In relation to local hydrodynamic effects, it is observed that currents increase at the side of the monopile and decrease in front of and downstream of the monopile. In relation to sediment transport effect, the results show that resuspension and erosion occur around the monopile in locations where the current speed increases due to the monopile presence, and sediments deposit downstream where the bed shear stress is lower. During the tidal cycle, wakes downstream of the monopile reach the following monopile and modify the velocity magnitude and suspended sediment concentration patterns around the second monopile. 相似文献
13.
A survey of urban climate change experiments in 100 cities 总被引：1，自引：0，他引：1
Cities are key sites where climate change is being addressed. Previous research has largely overlooked the multiplicity of climate change responses emerging outside formal contexts of decision-making and led by actors other than municipal governments. Moreover, existing research has largely focused on case studies of climate change mitigation in developed economies. The objective of this paper is to uncover the heterogeneous mix of actors, settings, governance arrangements and technologies involved in the governance of climate change in cities in different parts of the world.The paper focuses on urban climate change governance as a process of experimentation. Climate change experiments are presented here as interventions to try out new ideas and methods in the context of future uncertainties. They serve to understand how interventions work in practice, in new contexts where they are thought of as innovative. To study experimentation, the paper presents evidence from the analysis of a database of 627 urban climate change experiments in a sample of 100 global cities.The analysis suggests that, since 2005, experimentation is a feature of urban responses to climate change across different world regions and multiple sectors. Although experimentation does not appear to be related to particular kinds of urban economic and social conditions, some of its core features are visible. For example, experimentation tends to focus on energy. Also, both social and technical forms of experimentation are visible, but technical experimentation is more common in urban infrastructure systems. While municipal governments have a critical role in climate change experimentation, they often act alongside other actors and in a variety of forms of partnership. These findings point at experimentation as a key tool to open up new political spaces for governing climate change in the city. 相似文献
14.
Groundwater evolution and mean water age inferred from hydrochemical and isotopic tracers in a tropical confined aquifer 
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下载免费PDF全文 Pedro Villegas Vanesa Paredes Teresita Betancur Jean D. Taupin Luis E. Toro 《水文研究》2018,32(14):2158-2175
The coastal confined aquifer in the Gulf of Urabá (Colombia) is an important water source for the banana agro‐industry as well as for urban and rural communities. However, the main processes controlling recharge and mixing in the aquifer are still poorly understood. Hydrochemical analyses and stable isotope monitoring were conducted to (a) determine groundwater recharge origin, mean groundwater age, and the main processes governing groundwater chemistry and the potential mixing of marine water and the influence of diffusive processes from the two surrounding aquitard layers. Hydrochemical data indicate that the main processes affecting the dissolved chemical composition include cation exchange, dissolution of carbonated and CO2, and silicate weathering. δ18O and δ2H compositions combined with 14C data highlight the differences in climatic conditions between the recharge zone and the confined section of the aquifer, which is close to the Atlantic Ocean. Groundwater samples with 14C ages from recent to 28,300 years BP show a depleted isotopic trend ranging from ?6.43‰ to ?9.14‰ in δ18O and from ?43.2‰ to ?65.7‰ in δ2H. The most depleted δ18O and δ2H compositions suggest a cooler recharge climate than the current conditions (corresponding to the last glacial period of the late Pleistocene). Depleted δ13C values in the total dissolved inorganic carbon indicate the existence of organic material oxidation processes within the geologic formation. These results can be used or transferred to enhance groundwater modelling efforts in other confined coastal aquifers of South America where scarcity of long‐term monitoring data limits water resources planification under a changing climate. 相似文献
15.
It is estimated that more than three quarters of the Earth’s biosphere is in perennially cold environments. Despite the extreme environmental conditions of desiccation and freezing, microbes can coloni... 相似文献
16.
Modelling feedbacks between geomorphological and riparian vegetation responses under climate change in a Mediterranean context 下载免费PDF全文
下载免费PDF全文 Vanesa Martínez‐Fernández Mijke Van Oorschot Marta González del Tánago Anthonie D. Buijse 《地球表面变化过程与地形》2018,43(9):1825-1835
Climate change is expected to alter temperatures and precipitation patterns, affecting river flows and hence riparian corridors. In this context we have explored the potential evolution of riparian corridors under a dryness gradient of flow regimes associated with climate change in a Mediterranean river. We have applied an advanced bio‐hydromorphodynamic model incorporating interactions between hydro‐morphodynamics and vegetation. Five scenarios, representing drier conditions and more extreme events, and an additional reference scenario without climate change, have been designed and extended until the year 2100. The vegetation model assesses colonization, growth and mortality of Salicaceae species. We analysed the lower course of the Curueño River, a free flowing gravel bed river (NW Spain), as a representative case study of the Mediterranean region. Modelling results reveal that climate change will affect both channel morphology and riparian vegetation in terms of cover, age distribution and mortality. Reciprocal interactions between flow conditions and riparian species as bio‐engineers are predicted to promote channel narrowing, which becomes more pronounced as dryness increases. Reductions in seedling cover and increases in sapling and mature forest cover are predicted for all climate change scenarios compared with the reference scenario, and the suitable area for vegetation development declines and shifts towards lower floodplain elevations. Climate change also leads to younger vegetation becoming more subject to uprooting and flooding. The predicted reduction in suitable establishment areas and the narrowing of vegetated belts threatens the persistence of the current riparian community. This study highlights the usefulness of advanced bio‐hydromorphodynamic modelling for assessing climate change effects on fluvial landscapes. It also illustrates the need to consider climate change in river management to identify appropriate adaptation measures for riparian ecosystems. Copyright © 2018 John Wiley & Sons, Ltd. 相似文献
17.
Sensitivity analysis of main variables present in flash flood processes. Application in two Spanish catchments: Arás and Aguilón 总被引：1，自引：0，他引：1
Jesús Mateo Lázaro José Ángel Sánchez Navarro Alejandro García Gil Vanesa Edo Romero 《Environmental Earth Sciences》2014,71(6):2925-2939
The program Simulation of Hydrological Extreme Events provides a set of functionalities that combined together allows constructing, manipulating, analyzing and comparing the hydrological processes involved in flash flood generation. The program makes use of existing databases of interest in hydrology and available in Spain, such as digital terrain models, coverage of rainfall or curve number. Two pilot watersheds from Spain were selected, Arás and Aguilón, where flash flood episodes have taken place. A sensitivity analysis of the flash flood episodes in response to changes in the main hydrological processes involved has been made, such as spatial and temporal distribution of rainfall, soil moisture status and water flow through channel network. In this work, we found that the antecedent moisture condition is the most influential factor in the magnitude of flash floods produced by the same amount of rain. The temporal distribution of the storm represents the second characteristic in order of relevance. In addition, terrain morphology (specially the slope) is found to be decisive in the results differences obtained. 相似文献
18.
Joan E. Cartes Emanuela Fanelli Vanesa Papiol Leda Zucca 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(11):1485-1498
We analyzed the distribution, diversity, and composition of western Mediterranean macroplankton (excluding gelatinous taxa) in the water column over depths of ca. 550–850 m, with special attention to near-bottom (0–1.5 and ca. 5–77 m above the bottom, mab) levels, and including data from three areas (off the coasts of Catalonia, and to the NW, and SE of Mallorca, Balearic Islands) in the period 1991–2008. Spatio-temporal changes in macroplankton abundance were evaluated as follows: (i) by seasonal sampling in 2007 off the Catalonian coast, (ii) by comparing Catalonian and Balearic Island slopes, and (iii) by comparing a fixed station on the Catalonian slope (at 550–800 m depth) at decadal (1991/1992–2007/2008) time scales. Diversity (in terms of species richness, S) was greater (i) at ca. 5–77 mab than at 0–1.5 mab, (ii) over the insular slopes of the Balearic Island (around Mallorca) than over the mainland Catalonian slopes, and (iii) in the period 1991/1992 than in 2007, likely related to higher values of the North Atlantic Oscillation (NAO) index in 1991/1992. In most analyses species composition was strongly influenced by the degree of stratification and homogenization of the water column in summer–autumn and winter–spring respectively and by location (longitude). Changes consisted mainly of higher density of macroplankton (e.g. abundance of the dominant euphausiids Nematoscelis megalops, Meganyctiphanes norvegica and Euphausia krohni and of the fish Cyclothone braueri) between June and October, parallel to an increase in the T and S close to the bottom. This coincided with changes in the flow of Levantine intermediate water (LIW) in the area. Aggregation of adult forms of the dominant species close to the bottom in summer–autumn could be favored because summer is the period of highest density of food – copepods, mainly Calanus helgolandicus – near the bottom off the Catalan slope. The formation of a thermocline in the water column and the reinforcement of the permanent thermohaline front at the shelf-slope break during summer at ca. 400 m in the Balearic Basin may also enhance this tendency toward greater aggregation of deep macroplankton under stratified water column conditions. 相似文献
19.
María Eugenia Pérez González María del Pilar García Rodríguez Vanesa González-Quiñones Raimundo Jiménez Ballesta 《Environmental Geology》2006,51(1):143-149
The spatial variability of the quality of the soil on the shores of a lagoon affected by hydromorphy and/or salinity can be identified (Laguna de Villacañas, Castilla La Mancha) by the use of multitemporal Landsat images in order to analyse these changes. For this purpose, TM and ETM images along with field observations and certain edaphic laboratory parameters are used. In order to identify saline-hydromorphic soils, the spatial variability of chemical and physical properties of a transect, which includes from Solonchaks to Regosols and Cambisols, have been correlated with the Normalised Difference Vegetation Index (NDVI). This index, chosen for specific dates, has proven to be very useful in detecting halophytic vegetation and relating it to the variability of the quality of these soils. 相似文献
20.
Late Cenozoic brittle deformation in the Southern Patagonian Andes: Record of plate coupling/decoupling during variable subduction? 下载免费PDF全文
下载免费PDF全文 Vanesa Barberón Christian Sue Matías Ghiglione Gonzalo Ronda Eugenio Aragón 《地学学报》2018,30(4):296-309
The Andes of southern Patagonia experienced a Miocene shift towards faster and higher angle subduction followed by the approach and collision of the Chile oceanic ridge. We present a kinematic study characterizing palaeostress fields computed from brittle tectonics to better constrain upper crustal deformation during this complex scenario. Although previous studies already suggested variable kinematics, it is striking that in a long‐lasting subduction environment, the computed palaeostress tensors are mostly strike‐slip (55%), while 35% are extensional, and only 10% compressive which are concentrated along a main frontal thrust. Cross‐cutting relationships and synsedimentary deformation indicate that a long‐lived strike‐slip regime was punctuated by a lower Miocene extensional event in the foreland before the main compressional event. The results are discussed in contrasting geodynamic models of plate coupling/decoupling versus direction and rate of convergence of the subducting plate, to explain the main mechanisms that control back‐arc deformation. 相似文献