Genetic and morphological divergence in the purple sea urchin Paracentrotus lividus (Echinodermata, Echinoidea) across the African Mediterranean coast     

Temim Deli  Mohamed Hbib Ben Atti  Rym Zitari-Chatti  Khaled Sai  Noureddine Chatti 《海洋学报(英文版)》2017,36(12):52-66

The present investigation focuses on population structure analysis of the purple sea urchin Paracentrotus lividus across the African Mediterranean coast, with the main aim of assessing the influence of the Siculo-Tunisian Strait on gene flow disruption in this highly dispersive echinoid species. For this purpose, patterns of morphological and genetic variation were assessed among its populations from the western and eastern Mediterranean coasts. A total of 302 specimens from seven Tunisian sites were collected and examined for morphometric variability at twelve morphometric traits. Concordant results, inferred from CDA (canonical discriminant analyses), pairwise NPMANOVA (non parametric multivariate analysis of variance) comparisons and MDS (multidimensional scaling) plot, unveiled significant inter-population differences in the measured traits among the studied populations. Furthermore, the combined use of the one way ANOSIM (analysis of similarities) and the Discriminant/Hotelling analysis allowed unravelling two morphologically differentiated groups assigned to both western and eastern Mediterranean basins. The SIMPER (similarity percentages) routine analysis showed that total dry weight, test diameter and spine length were major contributors to the morphometric separation between locations and between groups. Pattern of phenotypic divergence discerned in P. lividus across the Siculo-Tunisian Strait is interestingly in congruence with that inferred from the genetic investigation of the purple sea urchin populations from the same region based on the analysis of the mtDNA COI (cytochrome oxidase I) gene in 314 specimens from nineteen locations covering a wider geographic transect, streching westward to the Algerian coast and eastward to the Libyan littoral. The specific haplotypic composition characterizing each Mediterranean basin, as inferred from the minimum spanning network, confirmed the geographic partioning of genetic variation, as revealed by F-statistics and AMOVA (analysis of molecular variance) analyses, yielding significant genetic differentiation between eastern and western Mediterranean populations. The newly detected phylogeographic patterns, observed for the first time in P. lividus throughout the explored distribution range, suggest the involvement of different biotic and abiotic processes in shaping such variation, and provide evidence that a large and geographically exhaustive dataset is necessary to unveil phylogeographic structure within widespread marine species, previously cathegorized as panmictic in part of their distribution range.  相似文献   

Rate of seawater intrusion estimated by geophysical methods in an arid area: Al Khabourah, Oman     

Osman A. E. Abdalla  Mubarik Ali  Khalifa Al-Higgi  Hilal Al-Zidi  Issa El-Hussain  Said Al-Hinai 《Hydrogeology Journal》2010,18(6):1437-1445

Seawater intrusion and its spreading rate are the challenging problems in over-pumped coastal aquifers of arid zones like the Batinah region of Oman. The study delineates the saline plume, identifies saline/freshwater zones, and estimates the migration rate of the plume in the Al Khabourah area of the Batinah coast. Time domain electromagnetic surveys, aided by vertical electrical sounding surveys, and seismic refraction methods have defined the locus of the saline/freshwater interface in the area. The current (2007) interface position, when compared with that determined during 2002, indicates a prominent recession in the saline plume and suggests an average annual recession rate of 120 m. This recession may be attributed mainly to the recharging dam of Wadi Al Hawasinah, constructed in 1995, and the enforcement of new water resources legislation. This study reveals the shielding role of the recharging dam to counter advancing saline intrusion.  相似文献   

Recent uplift and hydrothermal activity at Tangkuban Parahu volcano, west Java, Indonesia     

John Dvorak  Johannes Matahelumual  Arnold T Okamura  Harun Said  Thomas J Casadevall  Dedi Mulyadi 《Bulletin of Volcanology》1991,53(1):20-28

Tangkuban Parahu is an active stratovolcano located 17 km north of the city of Bandung in the province west Java, Indonesia. All historical eruptive activity at this volcano has been confined to a complex of explosive summit craters. About a dozen eruptions-mostly phreatic events- and 15 other periods of unrest, indicated by earthquakes or increased thermal activity, have been noted since 1829. The last magmatic eruption occurred in 1910. In late 1983, several small phreatic explosions originated from one of the summit craters. More recently, increased hydrothermal and earthquake activity occurred from late 1985 through 1986. Tilt measurements, using a spirit-level technique, have been made every few months since February 1981 in the summit region and along the south and east flanks of the volcano. Measurements made in the summit region indicated uplift since the start of these measurements through at least 1986. From 1981 to 1983, the average tilt rate at the edges of the summit craters was 40–50 microradians per year. After the 1983 phreatic activity, the tilt rate decreased by about a factor of five. Trilateration surveys across the summit craters and on the east flank of the volcano were conducted in 1983 and 1986. Most line length changes measured during this three-year period did not exceed the expected uncertainty of the technique (4 ppm). The lack of measurable horizontal strain across the summit craters seems to contradict the several years of tilt measurements. Using a point source of dilation in an elastic half-space to model tilt measurements, the pressure center at Tangkuban Parahu is located about 1.5 km beneath the southern part of the summit craters. This is beneath the epicentral area of an earthquake swarm that occurred in late 1983. The average rate in the volume of uplift from 1981 to 1983 was 3 million m³ per year; from 1983 to 1986 it averaged about 0.4 million m³ per year. Possible causes for this uplift are increased pressure within a very shallow magma body or heating and expansion of a confined aquifier.  相似文献   

HAPEX-Sahel: a large-scale study of land-atmosphere interactions in the semi-arid tropics   总被引：5，自引：0，他引：5  

J.-P. Goutorbe  T. Lebel  A. Tinga  P. Bessemoulin  J. Brouwer  A. J. Dolman  E. T. Engman  J. H. C. Gash  M. Hoepffner  P. Kabat  Y. H. Kerr  B. Monteny  S. Prince  F. Said  P. Sellers  J. S. Wallace 《Annales Geophysicae》1994,12(1):53-64

The Hydrologic Atmospheric Pilot EXperiment in the Sahel (HAPEX-Sahel) was carried out in Niger, West Africa, during 1991 - 1992, with an intensive observation period (IOP) in August - October 1992. It aims at improving the parameterization of land surface atmosphere interactions at the Global Circulation Model (GCM) gridbox scale. The experiment combines remote sensing and ground based measurements with hydrological and meteorological modelling to develop aggregation techniques for use in large scale estimates of the hydrological and meteorological behaviour of large areas in the Sahel. The experimental strategy consisted of a period of intensive measurements during the transition period of the rainy to the dry season, backed up by a series of long term measurements in a 1^ by 1^ square in Niger. Three “supersites” were instrumented with a variety of hydrological and (micro) meteorological equipment to provide detailed information on the surface energy exchange at the local scale. Boundary layer measurements and aircraft measurements were used to provide information at scales of 100 - 500 km². All relevant remote sensing images were obtained for this period. This programme of measurements is now being analyzed and an extensive modelling programme is under way to aggregate the information at all scales up to the GCM grid box scale. The experimental strategy and some preliminary results of the IOP are described.  相似文献   

Contamination status and assessment of urban and non-urban soils in the region of Sulaimani City,Kurdistan, Iraq     

Mohammad Said Hamma Khorshid  Sören Thiele-Bruhn 《Environmental Earth Sciences》2016,75(16):1171

  相似文献   

Application of kinematic vorticity and gold mineralization for the wall rock alterations of shear zone at Dungash gold mining,Central Eastern Desert,Egypt     

Osama M. K. Kassem  Said H. Abd El Rahim  EL Said R. El Nashar  Kaled M. AL Kahtany 《Geology of Ore Deposits》2016,58(6):499-515

The use of porphyroclasts rotating in a flowing matrix to estimate mean kinematic vorticity number (Wm) is important for quantifying the relative contributions of pure and simple shear in wall rocks alterations of shear zone at Dungash gold mine. Furthermore, it shows the relationship between the gold mineralization and deformation and also detects the orientation of rigid objects during progressive deformation. The Dungash gold mine area is situated in an EW-trending quartz vein along a shear zone in metavolcanic and metasedimentary host rocks in the Eastern Desert of Egypt. These rocks are associated with the major geologic structures which are attributed to various deformational stages of the Neoproterozoic basement rocks. We conclude that finite strain in the deformed rocks is of the same order of magnitude for all units of metavolcano-sedimentary rocks. The kinematic vorticity number for the metavolcanic and metasedimentary samples in the Dungash area range from 0.80 to 0.92, and together with the strain data suggest deviations from simple shear. It is concluded that nappe stacking occurred early during the underthrusting event probably by brittle imbrication and that ductile strain was superimposed on the nappe structure during thrusting. Furthermore, we conclude that disseminated mineralization, chloritization, carbonatization and silicification of the wall rocks are associated with fluids migrating along shearing, fracturing and foliation of the metamorphosed wall rocks.  相似文献   

Comparison of the growth and biomass production of six acacia species in Riyadh, Saudi Arabia after 4 years of irrigated cultivation     

Ibrahim M. Aref  L. I. El-Juhany  Said S. Hegazy 《Journal of Arid Environments》2003,54(4):783-792

The growth and biomass production of six acacia species were studied in the field for 4 years. The species used were Acacia asak, A. negrii, A. seyal, A. karroo, A. ampliceps, and A. stenophylla. The first three species are indigenous while the others are exotic. The results showed both A. ampliceps and A. asak with 100% survival while all A. negrii died. Acacia ampliceps attained the greatest height, diameter, relative growth rate and above-ground biomass while A. asak had the least. Height and diameter growth of acacia species decreased between warm and cold periods of the year.  相似文献   

Recent uplift and hydrothermal activity at Tangkuban Parahu volcano,west Java,Indonesia     

John Dvorak  Johannes Matahelumual  Arnold T Okamura  Harun Said  Thomas J Casadevall  Dedi Mulyadi 《Bulletin of Volcanology》1990,53(1):20-28

Tangkuban Parahu is an active stratovolcano located 17 km north of the city of Bandung in the province west Java, Indonesia. All historical eruptive activity at this volcano has been confined to a complex of explosive summit craters. About a dozen eruptions-mostly phreatic events- and 15 other periods of unrest, indicated by earthquakes or increased thermal activity, have been noted since 1829. The last magmatic eruption occurred in 1910. In late 1983, several small phreatic explosions originated from one of the summit craters. More recently, increased hydrothermal and earthquake activity occurred from late 1985 through 1986. Tilt measurements, using a spirit-level technique, have been made every few months since February 1981 in the summit region and along the south and east flanks of the volcano. Measurements made in the summit region indicated uplift since the start of these measurements through at least 1986. From 1981 to 1983, the average tilt rate at the edges of the summit craters was 40–50 microradians per year. After the 1983 phreatic activity, the tilt rate decreased by about a factor of five. Trilateration surveys across the summit craters and on the east flank of the volcano were conducted in 1983 and 1986. Most line length changes measured during this three-year period did not exceed the expected uncertainty of the technique (4 ppm). The lack of measurable horizontal strain across the summit craters seems to contradict the several years of tilt measurements. Using a point source of dilation in an elastic half-space to model tilt measurements, the pressure center at Tangkuban Parahu is located about 1.5 km beneath the southern part of the summit craters. This is beneath the epicentral area of an earthquake swarm that occurred in late 1983. The average rate in the volume of uplift from 1981 to 1983 was 3 million m³ per year; from 1983 to 1986 it averaged about 0.4 million m³ per year. Possible causes for this uplift are increased pressure within a very shallow magma body or heating and expansion of a confined aquifier.  相似文献   

Re-evaluations of seismic hazard of Iraq     

AbdulMuttalib Isa Said  Mustafa Shakir Farman 《Arabian Journal of Geosciences》2018,11(11):279

In recent years, Iraq has experienced an increase in seismic activity, especially, near the east boundary with Iran. Previous studies present their results in terms of PGA and for return periods of 500 years and less, and other studies not continued to include the whole PSHA process whereas some recent studies continued to include the whole PSHA process using earthquakes data till 2009 including dependent events. This study includes two main stages, the first is collecting the earthquakes records including the recent events till the end of March 2016 and applying data processing to get the net catalog to independent events. The second stage is applying the steps of PSHA method. Matlab programs have been built to execute these two stages and to convert the results of PSHA computations into contours of 5% damping PGA and spectral accelerations at 0.2 and 1.0 s for a return period of 2475 years, and for rock sites. Also, spectral acceleration against period has been presented for main cities. Also, the PGA map, for a return period of 475 years, has been plotted and then prepared together with similar maps of neighbor countries in one map for comparison. In general, this comparison indicates the similarity in behavior but, the values reveal a relative agreement and they are between Turkish and Iranian values.  相似文献   

The November 26 and 27, 1927 devastating flood event (NW Algeria): characterization and reconstruction using historical data     

Miloud Sardou  Said Maouche  Bendehiba Sabeur  Hanifi Missoum 《Arabian Journal of Geosciences》2018,11(10):229

The historical records show that the Northwestern Algeria has experienced more than 130 floods, which were sometimes catastrophic. They caused more than 1000 deaths and significant damage. In this work, we try to reconstruct the most devastating and deadly historical flood that occurred on November 26 and 27, 1927. This event is interesting to discuss disaster scenario because of its extent and impacts and the availability of data. For this purpose, we used historical press reports, scientific papers, and archival reports. This work allowed the reconstruction of the hydroclimatic situation during the flood and the regional scale impacts. It presents also the catastrophic flooding of the Ain Sefra river at Mostaganem and that of El Hammam river, as well as the Fergoug dam breaking at Mohammadia. The main factor triggering these floods was the heavy rainfall. Other factors have increased the damage such as the occupation of high-risk areas and the human failure. This event caused 430 killed persons, more than 1200 disaster victims, and around one billion francs losses. These effects evidence the high vulnerability of the Northwestern Algeria to the occurrence of floods. For that, if a similar event occurs in the future, it can be extremely negative.  相似文献