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61.
Predation has received considerable theoretical and empirical support in population regulation. The effect of predators, however, could be achieved in direct (killing) or indirect effects (such as displacement). In this paper, we explored the relationship between Eurasian kestrels Falco tinnunculus and skylarks Alauda arvensis in Mediterranean grasslands. First, we analysed the presence of skylarks in the kestrel diet over 9 years. We also compared a grassland area of experimentally increased kestrel density and a second grassland as control area to evaluate the direct or indirect effect on skylark abundance. We also considered two different habitats, grazed and ungrazed plots. If skylark abundance decreased as the kestrel breeding season progressed in high-density kestrel area compared with the control area, it would suggest a direct effect (predator hypothesis). If skylark abundance remains constant in both areas of contrasting kestrel density, it would suggest that skylarks avoid kestrels (avoidance hypothesis). We found that skylark abundance decreased in the kestrel area from the beginning of kestrel nest-box installation to recent years. The rate of skylark consumption decreased in a 9-year period as kestrel abundance increased, although the total amount skylark consumption did not show a decreasing trend. In addition, skylarks were more abundant in the kestrel-free area than in the kestrel area. Finally, we found that skylark abundance did not change through the kestrel breeding period in relation to grazing. We suggest that an increased breeding density of kestrels during their breeding period may force the skylarks to breed in other areas, which may explain the decline of their abundance. 相似文献
62.
Towards an inter-disciplinary research agenda on climate change, water and security in Southern Europe and neighboring countries 总被引:1,自引:0,他引:1
Ralf Ludwig Roberto Roson Christos Zografos Giorgios Kallis 《Environmental Science & Policy》2011,14(7):794-803
The Mediterranean and neighboring countries are already experiencing a broad range of natural and man-made threats to water security. According to climate projections, the region is at risk due to its pronounced susceptibility to changes in the hydrological budget and extremes. Such changes are expected to have strong impacts on the management of water resources and on key strategic sectors of regional economies. Related developments have an increased capacity to exacerbate tensions, and even intra- and inter-state conflict among social, political, ecological and economic actors. Thus, effective adaptation and prevention policy measures call for multi-disciplinary analysis and action.This review paper presents the current state-of-the-art on research related to climate change impacts upon water resources and security from an ecological, economic and social angle. It provides perspectives for current and upcoming research needs and describes the challenges and potential of integrating and clustering multi-disciplinary research interests in complex and interwoven human-environment systems and its contribution to the upcoming 5th assessment report of the IPCC. 相似文献
63.
We evaluated the use of Talitrus saltator as biomonitor of polychlorinated byphenyls (PCBs) contamination of the supralittoral zone of Mediterranean sandy shores, an area not yet investigated about the presence of these pollutants. Twenty of 22 PCB congeners analysed were detected and quantified in sand and sandhoppers' samples collected in 6 different sites along the Tyrrhenian coast of Central Italy. Among the congeners analysed, PCB 153 and PCB 138 were the most abundant both in amphipods and sand samples and, regarding the congener pattern analysis, hexa-, hepta- and penta-PCBs were the most abundant congeners in sandhoppers. Though hydrophobic compounds, such as PCBs, bind strongly to sand and sediments, PCB concentrations were higher in T. saltator than in the sand revealing a good ability of this species to accumulate this class of contaminants. The concentration of each PCB congener recorded in tissues of sandhoppers showed significant differences among sampling sites revealing a good ability of these species to accumulate PCBs at different concentrations depending on the contamination levels of the sampling site. Therefore, our results suggest the possible utilisation of T. saltator as a biomonitor of PCB contamination of the supralittoral zone of Mediterranean sandy shores. 相似文献
64.
Data on Cd, Pb and Cu concentrations in seawater referring to five years of field studies on the western Mediterranean Sea are reported in order to present a space and time integrated situation on the levels of these metals. Surface total metal concentrations present rather homogeneous distributions between the different areas considered, including the Tyrrhenian Sea. The metal concentrations in three areas affected by natural and industrial wastes are also discussed. The vertical distribution of the dissolved Cd, Pb and Cu in the Alboran Sea seems to be rather homogeneous, both vertically and among the stations chosen between the Strait of Gibraltar and the Island of Alboran. 相似文献
65.
Vermetid reefs are among the most important bioconstructions in the Mediterranean Sea, with a distribution restricted to the warmest part of the basin. Their structure, and vertical and geographical distribution make them good biological indicators of changes in sea level and sea-surface temperature over the last two millennia. 相似文献
66.
Spatial and temporal changes in the biochemical composition of particulate organic matter in a semi-enclosed marine system (Stagnone di Marsala, Mediterranean Sea) were studied, on a monthly basis, from January to December 1994, in order to assess nutritional value of suspended particles for benthic suspension feeders. According to previous findings, the study site displayed a strong oligotrophy. Chlorophyll-a accounted for a very low fraction of the total suspended matter pool (0.1%), whereas at least 75% of POC was of detrital/heterotrophic origin. POC: PON ratio values indicate that bacterioplankton biomass accounted for a significant fraction of the total POC pool, displaying values comparable to those of the phytoplankton biomass (phytoplankton to bacterial biomass ratio was about (1). Temporal and spatial changes in the biochemical composition of particulate organic matter were rather limited and related to its sources, the main of which is represented by detrital particles released by the Posidonia oceanica (L.) beds. the comparison between our results and those encountered in other coastal lagoons indicates that the low abundance of suspension-feeding organisms observed in the study area is related to the “quality depression” of particles due to the dilution of high quality compounds (i.e., biopolymeric carbon) in a largely inorganic matrix. This result leads us to conclude that, to reach the same amount of high quality particulate food, a suspension feeder mollusc in the Marsala lagoon would need to filter a sea water volume around 3 times higher than in other Mediterranean coastal lagoons. 相似文献
67.
Heavy metal concentrations (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were determined in various tissues (hepatopancreas, branchial hearts, salivary gland, gills, genital tract, mantle, arms and skin) of Octopus vulgaris collected from three different contaminated sites in front of Alexandria (Egypt) during 2000. All collected tissues displayed high enrichment factors when compared to ambient levels. Heavy metal concentrations in most tissues displayed significant differences among sites, sizes and sex. This study suggests that hepatopancreas, and to a lesser extent branchial hearts, are better indicators of chronic Cu, Fe, Zn and Cd contamination than edible tissues. The enrichment factor (EF) for heavy metals in the hepatopancreas and in edible tissues allowed discriminating our samples into three main groups; (1) EF?>?55 (Cu), (2) EF ranging from 15 to 7.5 (Fe, Cd and Zn) and (3) EF?2.5 (Mn, Co, Pb, Ni and Cr). In the Mex area, the most polluted site, the highest bioaccumulation of Cu, Fe, Zn and Mn was observed. In the Kayet Bey were observed high levels of Pb and in Agami high concentrations of Cd were recorded. Females bioaccumulated Pb and Fe and less Zn, Cr, and Co than males, whereas Ni and Mn concentrations were sex independent. Concentrations of both Mn and Co in gonads, Cr in branchial hearts and Zn in both gills and mantle increased linearly with animal weight. Conversely, concentrations of Cd and Ni in gonads, Mn in mantle and Pb in hepatopancreas were inversely related with body size. Finally, heavy metal bioaccumulations in the liver were independent from animal size. 相似文献
68.
A. Bellante M. Sprovieri G. Buscaino D. Salvagio Manta G. Buffa V. Di Stefano 《Chemistry and Ecology》2013,29(5):311-323
Trace element concentrations (chromium, copper, zinc, iron, manganese and vanadium) were determined in organs of five species of cetaceans (Stenella coeruleoalba, Tursiops truncatus, Grampus griseus, Physeter macrocephalus, Ziphius cavirostris) that were found stranded along Italian coasts in the period 2000–2009. This dataset represents an important opportunity to verify and assess (particularly for V) patterns of incorporation of trace elements in different organs of cetaceans in a wide spectrum of species and related specimens distributed in all the age classes, and consequently determine the physiological and metabolic effects on the distribution modes of the same chemicals. In particular, Cu, Zn, and Fe accumulate preferentially in the liver of all studied specimens, while Mn and Cr values are found to be nearly constant in the analysed organs and tissues regardless of species. Comparable concentrations of trace elements, in different age classes, were measured for both specimens of S. coeruleoalba and T. truncatus (the most abundant dolphin species in the Mediterranean sea) in all analysed organs. On the other hand, unprecedented reported concentrations of V in tissues and organs of cetaceans from the Mediterranean show higher values when compared to levels measured in other marine mammals from the Atlantic Ocean. 相似文献
69.
Serena Risica 《Chemistry and Ecology》2013,29(4):225-230
Following a similar project performed for the Northern European Seas in the years 1985–1990, a study on the radioactive contamination of the Mediterranean Sea has recently been conducted by a group of experts of the European Union (MARINA-MED Project). Its aim was to assess the radiological exposure of the population of the European Union, due both to natural and man-made radionuclides in the Mediterranean Sea. A review of the conclusions of this study is presented, with special attention to the environmental radioactive data. the Italian radioactive monitoring organisation is described. Starting from this experience, some proposals for new research projects are presented. 相似文献
70.
Abstract The Rhône delta is a typical microtidal estuary. River runoff spreads out into the Gulf of Lions as a surface plume influenced by the prevailing N or NW wind and the Liguro-Provençal-Catalan current. in the prodelta, sediments form a filter that traps radionuclides released by the different nuclear installations on the Rhône River and which are associated with fine particles. the horizontal distribution of various artificial radionuclides shows the highest concentrations at the Rhône River mouth. There,137Cs reaches 86.6 and 94.4 Bq·kg?1 dry wt. and is still present 10 miles away (32.5 Bq·kg?1 dry wt.) in the southwestward direction (influence of the general circulation). Data obtained in the sediment at Roustan station between 1980 and 1990 show that in 1990, 137Cs levels were similar to those found previous to the Chernobyl accident. 相似文献