Genetic variability of the Lessepsian migrant mussel Brachidontes pharaonis (Bivalvia: Mytilidae) in Tunisia

The present study used two mitochondrial markers (16S rRNA and COI) to assess the genetic diversity of a newly founded Lessepsian migrant mussel, Brachidontes pharaonis, in Tunisian waters. The species appears to be restricted to only one population in Rades Harbour, in the northern part of the country. Phylogenetic analyses revealed the monophyly of B. pharaonis in Tunisia. Both molecular markers revealed high genetic variability of the B. pharaonis population. Haplotype networks and demographic analyses confirmed the recent expansion events within this population. Multiple human-mediated introduction events involving several founder populations and intensive population growth rates are probably the main causes of the high polymorphism observed within this invasive mollusc.     

Post-earthquake economic resilience and recovery efficiency in the border areas of the Tibetan Plateau: A case study of areas affected by the Wenchuan Ms 8.0 Earthquake in Sichuan,China in 2008

Journal of Geographical Sciences - The border areas of the Tibetan Plateau and the neighboring mountainous areas have a high incidence of earthquakes with a magnitude greater than Ms 5.0, as well...     

桐柏县固庙—新集1：20万金银异常评价方法及效果

随着河南区域化探扫面工作的结束，异常评价是摆在我们面前的当务之急。近年来，随着地质工作的不断深入，我们在异常评价程序及方法上作了一些探索，下面以桐柏县固庙—新集１：２０万金银异常评价方法及效果为例，重点加以讨论。     

Fishing industry and related perspectives on the issues raised by no-take marine protected area proposals

In the face of growing calls for no-take marine protected areas (NTMPAs), the views of fishing industry representatives in south-west (SW) England on related issues are analysed. Only 23% thought NTMPAs were the way forward and a range of concerns were expressed, e.g. that the ‘terrestrial’ protected areas approach and related biodiversity conservation objectives will be extended to the seas, and that fish yield reductions from the loss of access to NTMPAs are very unlikely to be compensated for through spillover/export. Some interesting approaches to ameliorating these concerns emerged, such as being open and honest that NTMPAs are primarily intended to achieve biodiversity conservation benefits, reducing uncertainty concerning the potential for any secondary fisheries spillover/export benefits, justifying NTMPAs on an objective, rational basis rather than on a subjective, precautionary basis, and the quid pro quo streamlining of wider fisheries management approaches. This research reveals a more diverse range of perspectives amongst fishing industry representatives on the issues raised by NTMPA proposals than is often assumed.     

The Upper Pleistocene to Holocene sediments on the Mediterranean island of Lampedusa (Italy)

The island of Lampedusa lies on the northern edge of the African continental shelf, but during some Quaternary marine lowstands it was joined to the African continent. The study and dating of the aeolian, alluvial, detrital sediments, calcareous crusts and speleothems have established that the climatic–environmental variations recorded on the island can be related chronologically to those known for northern Libya, Tunisia and the Italian peninsula. During the Last Glacial Maximum, phases of Saharan dust accumulation on Lampedusa occurred, and were coeval with dust accumulation in crater lakes and on high mountains in central‐southern Italy, and with phases of glacial advance in the Apennines and in the Alps. During the late Holocene, accumulation of Saharan dust on Lampedusa occurred but there was little accumulation of dust on the northern side of the Mediterranean Sea. With the new data from Lampedusa, it is possible to envisage two different scenarios of atmospheric circulation relating to the Last Glacial Maximum and to the late Holocene. During the Last Glacial Maximum, southerly atmospheric circulation brought rainfall to the southern slopes of the Alps and to the Apennines. During the late Holocene, a prevalent westerly atmospheric circulation became established in the northern Mediterranean. Copyright © 2004 John Wiley & Sons, Ltd.     

Crustal motion and deformation in Greece from a decade of GPS measurements, 1993–2003

The Hellenic plate boundary region, located in the collision zone between the Nubian/Arabian and Eurasian lithospheric plates, is one of the seismo-tectonically most active areas of Europe. During the last 15 years, GPS measurements have been used to determine the crustal motion in the area of Greece with the aim to better understand the geodynamical processes of this region. An extended reoccupation network covering whole Greece has been measured periodically in numerous GPS campaigns since the late eighties, and a continuous GPS network has been operated in the region of the Ionian Sea since 1995. In this paper, we present a new detailed high-quality solution of continuous and campaign-type measurements acquired between 1993 and 2003. During the GPS processing, a special effort was made to obtain consistent results with highest possible accuracies and reliabilities. Data of 54 mainly European IGS and EUREF sites were included in the GPS processing in order to obtain results which are internally consistent with the European kinematic field and order to allow for a regional interpretation. After an overview of the results of the IGS/EUREF sites, the results from more than 80 stations in Greece are presented in terms of velocities, time series, trajectories and strain rates. Previous geodetic, geological and seismological findings are generally confirmed and substantially refined. New important results include the observation of deformation zones to the north and to the south of the North Aegean Trough and in the West Hellenic arc region, arc-parallel extension of about 19 mm/yr along the Hellenic arc, and compression between the Ionian islands and the Greek mainland. Due to continuous long-term observations of 4–8 years, it was possible to extract height changes from the GPS time series. In Greece, we observe a differential subsidence of the order of 2 mm/yr between the northern and central Ionian islands across the Kefalonia fault zone. The differential subsidence of the central Ionian islands with respect to the northwestern Greek mainland amounts to 4 mm/yr.     

Vulnerability and fate of a coastal sand dune complex,Rosetta-Idku,northwestern Nile Delta,Egypt

Types, distribution, and origin of recent sand dunes between Rosetta and Idku, in the western sector of the Nile Delta, Egypt were investigated. Sand samples from the dunes, beach, and seafloor were studied for grain size distribution and mineralogical composition. It has been found that most of the dunes in the study area have been subjected to deterioration and removal due to the construction of buildings and the International Coastal Highway. The remnant constitutes a damaged belt of foredunes that extends from El Bouseily village to the west of Idku town. The dune’s origin is interpreted to be the result of coastal drifting and the subsequent transport of sediments of the former Canopic Nile branch eastward by the predominant longshore current and by aeolian processes. The blown sand grains accumulated to form a belt of coastal sand dunes of original longitudinal and crescentic forms. Urbanization of the coast has severely altered the landscape. The study area is considered vulnerable to the impacts of climate change and the expected rise in sea level. The outcome of potential sea level rise is serious; erosion problems are expected to be exacerbated and vast areas from land and property would be lost. Thus, protection and preservation the remaining dunes in the study area are vital requirements for shore protection.     

A comparative study of four vulnerability mapping methods in a detritic aquifer under mediterranean climatic conditions

This paper presents the results of a comparative study relating to the application of four vulnerability mapping methods, GOD, AVI, DRASTIC and SINTACS, in a pilot detritic aquifer situated in NW Morocco, known as the Martil–Alila aquifer. The principal objective of this work is to determine the most suitable such methods for this aquifer type within a Mediterranean context, and to show the effect of the rainfall variations that are characteristic of the Mediterranean climate on the degree of vulnerability. The methods applied distinguish five classes of vulnerability, these being irregularly divided up in space, with the division varying according to the method in question. The vulnerability maps obtained by the different methods strongly suggest that the eastern half of the aquifer is more vulnerable to contamination than the western half, for all hydrological situations. The effect of climatic conditions on the degree of vulnerability is well represented by the DRASTIC, according to which the aquifer is moderately to strongly vulnerable during humid hydrological years and weakly to moderately vulnerable during dry ones. For the other methods, this climatic effect is limited to the area occupied by the two predominant classes (“High” and “Low” for GOD and “High” and “Moderate” for SINTACS) while it is null for AVI. In conclusion, DRASTIC appears the most suitable for mapping the vulnerability to contamination of Mediterranean coastal detritic aquifers such as the Martil–Alila aquifer.     

Methodology of hydrogeological characterization of deep carbonate aquifers as potential reservoirs of groundwater. Case of study: the Jurassic aquifer of <Emphasis Type="Italic">El Maestrazgo</Emphasis> (Castellón,Spain)

A methodology for the characterization of deep carbonate aquifers has been developed and applied to El Maestrazgo Jurassic aquifer in Castellón, Spain. Characterization of these aquifer formations, located at more than 300 m deep, consisted of a previous phase of compilation, analysis and synthesis of the existing information about the area, followed by a coordinated combination of different speciality studies: geology, stratigraphy, structural analysis, hydrogeology, hydrochemistry, geophysics and remote sensing. Geological studies included geological mapping, definition of stratigraphical units and facies and structural analysis. The aim of the hydrogeology study was to define aquifer formations, recharge area, aquifer points inventory and groundwater flow directions for the establishment of piezometric and water quality observation nets. Special techniques were applied, like thermal infrared aerial images and the evaluation of submarine groundwater discharge by means of natural radium isotopes. Hydrochemical techniques, including majority elements characterization and stable isotopes (¹⁸O, ²H and ³H) determination, allowed classifying hydrochemical facies and establishing a renewal pattern for water within the system. Geophysics was useful in determining the aquifer geometry, the features of the basement and the petrophysical characteristics of the geological formations. Preliminary results show an important tectonic complexity and the possibilities for groundwater uses in the area of study.     

Diurnal changes in the bio-optical properties of the phytoplankton in the Alborán Sea (Mediterranean Sea)

The changes in the phytoplankton absorption properties during a diurnal cycle were investigated at one station located in the north-western area of the Alborán Sea. The experiment was performed in spring when the water column was strongly stratified. This hydrological situation permitted the establishment of a deep chlorophyll a (chl a) fluorescence maximum (DFM) which was located on average close to the lower limit of the mixed layer and the nutricline. The relative abundance of pico-phytoplankton (estimated as its contribution to the total chl a) was higher in the surface, however, micro-phytoplankton dominated the community at the DFM level. Chl a specific absorption coefficient (a*(λ)) also varied with optical depth, with a* (the spectrally average specific absorption coefficient) decreasing by 30% at the DFM depth with respect to the surface. A significant negative correlation between the contribution of the micro-phytoplankton to the total chl a and a* was obtained indicating that a* reduction was due to changes in the packaging effect. Below the euphotic layer, a* increased three-fold with respect to the DFM, which agrees with the expected accumulation of accessory pigments relative to chl a as an acclimation response to the low available irradiance. The most conspicuous change during the diurnal cycle was produced in the euphotic layer where the chl a concentration decreased significantly in the afternoon (from a mean concentration of 1.1 μg L⁻¹ to 0.7 μg L⁻¹) and increased at dusk when it averaged 1.4 μg L⁻¹. In addition, a* and the blue-to-red absorption band ratio increased in the afternoon. These results suggest that a*(λ) diurnal variability was due to increase in photo-protective and accessory pigments relative to chl a. The variation ranges of a*(λ) at 675 and 440 nm (the absorption peaks in the red and blue spectral bands, respectively) in the euphotic layer were 0.01–0.04 and 0.02–0.10 m² mg⁻¹ chl a, respectively. Approximately 30% out of this variability can be attributed to the diurnal cycle. This factor should therefore be taken into account in refining primary production models based on phytoplankton light absorption.