Environmental concerns for marina planning in the Gulf of Suez

This paper presents a case study where numerical modelling was utilized for the first time to estimate shoreline changes during the planning of a private pleasure marina in the Gulf of Suez. The study was made to compliment an environmental impact assessment study (EIA) requested by the Egyptian Environmental Affairs Agency (EEAA). The paper presents data collected during two surveys and the results of the numerical model. The impact of the marina on the sediment budget was investigated using the GENESIS one-line program. One of the main reasons for the study was to confirm that the choice of the marina location ensured minimum erosion of the shoreline. In the model, the sediment transport calibration constants were determined using the results of two surveys. The choice of the formula is discussed in the paper. Two locations for the marina were tested against minimum erosion at the down drift side of the marina. This study was performed in close co-ordination with the EEAA and several solutions were suggested to minimize the expected accretion before the final location was approved.     

An assessment of heavy-metal contamination in surface sediments of the Suez Gulf using geoaccumulation indexes and statistical analysis

An assessment of marine pollution due to metals was made in the Suez Gulf based on surface costal sediment collected from 18 locations along the Gulf. The samples were dried and acid-digested, and the metal contents (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) were determined using a flame atomic absorption spectrophotometer (air-acetylene) with deuterium background correction. An evaluation of the heavy-metal pollution status of the Gulf was carried out using enrichment factors (EF) and geo-accumulation Indexes (I_geo). Also, heavy-metal concentrations in Suez Gulf sediments were evaluated using the Effect Range-Low (ERL) and the Effect Range-Median (ERM). The results of a Spearman correlation and factor and cluster analysis of the heavy metals analysed in the collected sediment were discussed. The main source of contamination is offshore oil field and industrial wastes, which arise due to the ineffective and inefficient operation equipments, illegal discharge and lack of supervision, and prosecution of offenders.     

GIS and remote sensing as tools for conducting geo-hazards risk assessment along Gulf of Aqaba coastal zone,Egypt

Satellite remote sensing data, in addition to Geographic Information Systems (GIS), offers an excellent alternative to conventional mapping techniques in monitoring and mapping of geo-hazards areas. One of the most sustainable development projects in Egypt has been accomplished in Sinai, especially along and around the Gulf of Aqaba and the Gulf of Suez. Variations along the coastal zone of the Gulf of Aqaba have been identified through the analysis of multi-temporal satellite images with the aid of GIS analysis. The study area is subject to rapid and increasing changes in land-use/land-cover that resulting from natural and human activities such as flash flooding, seismic activity, landslides, and tourist and urban activities. This is in addition to the construction projects of roads, ports, PowerStation stations, mineral exploration, beaches, and tourist villages resulting from major environmental impacts. The current study aims to use Remote Sensing and GIS tools to investigate, monitor, and assess geo-hazards through the building of a geographical database. Several techniques have been developed over the last decade mostly to study the geological and geomorphologic characteristics of the terrain; land-use and land-cover changes. These are based on satellite imagery and Digital Elevation Models (DEM) to determine the topographic features, and geo-hazards maps. It is concluded that integrated approaches to monitoring can successfully be used to assess the environmental impacts along the Gulf of Aqaba coastal zone.     

Dissolved trace-metal concentrations along the Mediterranean Sea, to the north of the Nile Delta Region, Egypt

This work focuses on four marine sites of the Mediterranean Sea, north of the Nile Delta, Egypt. Surface-water samples were collected seasonally during 2003. The aim of this study is to assess the levels of some dissolved trace metals (Fe, Mn, Zn, Cu, and Pb) in two environmental conditions. The metal concentrations in the coastal zone were in the following ranges: 11.92-30.45 μg l^-1 for Fe, 5.79-17.36 μg l^-1 for Mn, 0.87-7.80 μg l^-1 for Zn, 0.40-1.87 μg l^-1 for Cu, and 1.53-10.31 μg l^-1 for Pb. In the sites with continental water input (mixing zone), the metals were scattered in the following ranges: Fe (19.72-60.33 μg l^-1), Mn (12.63-35.60 μg l^-1), Zn (2.67-22.00), Cu (0.83-8.10 μg l^-1), and Pb (1.72-29.7 μg l^-1). The results for the metal concentrations showed a remarkable decrease in the levels of the different metals going from the estuaries and outlets into the coastal sea water. Generally, the levels of the metals in the two zones are higher than the background levels of the unpolluted area. A comparison of the trace-metal levels in the coastal zone of the Mediterranean Sea north of Nile Delta with the minimal risk concentration (reported by water-quality criteria, WQC) showed a significantly lower content at the coastal area of the Mediterranean sea of Egypt. The study also indicated that the impact of anthropogenic inputs was limited in the distribution of the metals, except that the Pb content was slightly higher in the area of the mixing zone than that reported for WQC. The relationships between the different trace-metal concentrations and the other parameters (salinity, chlorophyll a and suspended particulate matter) were discussed, and the simple regressions between them were evaluated.     

Distribution of polychlorinated dibenzo-p-dioxins,polychlorinated dibenzofurans,dioxin-like polychlorinated biphenyl and polycyclic aromatic hydrocarbons in the sediment of Temsah lake,Suez Canal,Egypt

Lake Temsah is one of the main wetlands in the Suez Canal region, and the main source for fish for the area. The lake is the end-point of several wastewater effluents. In the present study, residues of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyl (PCB) and polycyclic aromatic hydrocarbons (PAH) were monitored in the sediment of the lake. Samples were collected from six different sampling stations around the lake using a box-corer sampler, then kept frozen. Samples were extracted and cleaned up before residue determination was conducted using an HRGC/HRMS. An HP 6890 plus gas chromatograph was coupled to a Micromass Autospec Ultima mass spectrometer operating in EI mode at 35 eV and with a resolution of 10.000 (5% valley). PCDDs and PCDFs were detected in all sediment samples collected from various sampling stations. Results showed some progressive increase in PCDDs concentrations relevant to increase in chlorination. In the PCDD group of congeners, 1, 2, 3, 4, 6, 7, 8, 9 octa-CDD had the highest detected concentrations in all samples, while 2, 3, 7, 8 tetra-CDD showed the lowest concentrations. The World Health Organization toxicity equivalents ranged from 0.387 to 11.20 ng kg^?1 d.w. For PCDD homologues, hexa-CDD was the most dominant homologue in all sediment samples analysed. Regarding dioxin-like PCBs, results showed that IUPAC No. 118 congener, 2, 3, 4, 4, 5, pentachlorobiphenyl was the most concentrated of all detected congeners, with concentrations ranging between 0.039 and 43.201 µg kg^?1. For polycyclic aromatic hydrocarbons, benzo(b+k+j)fluoranthene had the highest concentrations in almost all sampling stations. However, fluorene was the smallest detected concentration in almost all stations. This result would indicate that PAH contamination of the lake seems to be coming from one main source in all sampling stations. The present work is the first record of PCCDs, PCCFs, and dioxin-like PCBs in the Temsah lake. The concentrations of the contaminants monitored in this study, especially those of PAHs, are rather alarming. Efforts should be made to stop point sources that contaminate the lake.     

Distribution of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, dioxin-like polychlorinated biphenyl and polycyclic aromatic hydrocarbons in the sediment of Temsah lake, Suez Canal, Egypt

Lake Temsah is one of the main wetlands in the Suez Canal region, and the main source for fish for the area. The lake is the end-point of several wastewater effluents. In the present study, residues of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyl (PCB) and polycyclic aromatic hydrocarbons (PAH) were monitored in the sediment of the lake. Samples were collected from six different sampling stations around the lake using a box-corer sampler, then kept frozen. Samples were extracted and cleaned up before residue determination was conducted using an HRGC/HRMS. An HP 6890 plus gas chromatograph was coupled to a Micromass Autospec Ultima mass spectrometer operating in EI mode at 35 eV and with a resolution of 10.000 (5% valley). PCDDs and PCDFs were detected in all sediment samples collected from various sampling stations. Results showed some progressive increase in PCDDs concentrations relevant to increase in chlorination. In the PCDD group of congeners, 1, 2, 3, 4, 6, 7, 8, 9 octa-CDD had the highest detected concentrations in all samples, while 2, 3, 7, 8 tetra-CDD showed the lowest concentrations. The World Health Organization toxicity equivalents ranged from 0.387 to 11.20 ng kg^-1 d.w. For PCDD homologues, hexa-CDD was the most dominant homologue in all sediment samples analysed. Regarding dioxin-like PCBs, results showed that IUPAC No. 118 congener, 2, 3, 4, 4, 5, pentachlorobiphenyl was the most concentrated of all detected congeners, with concentrations ranging between 0.039 and 43.201 µg kg^-1. For polycyclic aromatic hydrocarbons, benzo(b+k+j)fluoranthene had the highest concentrations in almost all sampling stations. However, fluorene was the smallest detected concentration in almost all stations. This result would indicate that PAH contamination of the lake seems to be coming from one main source in all sampling stations. The present work is the first record of PCCDs, PCCFs, and dioxin-like PCBs in the Temsah lake. The concentrations of the contaminants monitored in this study, especially those of PAHs, are rather alarming. Efforts should be made to stop point sources that contaminate the lake.     

Hydrogeochemistry study and groundwater quality assessment in the north of Isfahan,Iran

This study presents the groundwater quality assessment in the north of Isfahan, Iran. In the study area, assessment and measurement of groundwater hydrochemical parameters such as pH, total dissolved solids (TDS), electrical conductivity (EC), sodium absorption ratio (SAR), total hardness, major cations (K⁺, Na⁺, Ca²⁺ and Mg²⁺) and major anions (Cl^?, \({\text{HCO}}_{ 3}^{ - } ,{\text{CO}}_{3}^{2 - }\) and \({\text{SO}}_{4}^{2 - }\)) concentrations were performed. Accordingly, the 66 water samples from different locations were collected during April and May 2015. Water samples collected in the field were analyzed in the laboratory for cations and anions using the standard methods. In this research, the analytical results of physiochemical parameters of groundwater were compared with the standard guideline values as recommended by the world health organization (WHO) for drinking and public health purposes. The pH values of groundwater samples varied from 7.05 to 8.95 with a mean of 7.78, indicating a neutral to slightly alkaline water. TDS values showed that 14% of the samples exceeds the desirable limit given by WHO. EC values varied from 213 to 4320 µS/cm, while 23% of the samples were more than the standard limit. Gibbs diagram had shown that 90% of the samples in the study area fall in the rock weathering zone, and this means that chemical weathering of rock-forming minerals is the main factor controlling the water chemistry in the study area. Irrigation suitability and risk assessment of groundwater are evaluated by measuring EC, %Na, SAR and RSC. According to the dominant cations and anions, five types of water were identified in the water samples: Ca-HCO₃, Ca-SO₄, Na-Cl, Na-HCO₃ and Na-SO₄. The results show that the majority of samples (30 samples, 45%) belongs to the mixed Na-SO₄ water type. Correlation analysis and principal component analysis was used to identify the relationship between ions and physicochemical parameters. Results indicated that 18 stations of the study area had the best quality and can be used for irrigation and drinking purposes in the future.     

A GIS-based vulnerability assessment of coastal natural hazards,state of Pará, Brazil

Studies carried out in the NE coastal zone of the State of Pará (Brazil) have recorded, in the last 25 years, numerous evidence of natural impacts of the flood and erosion processes. As a consequence, diverse strategies and measures of population adaptation have been implemented but with limited success. Therefore, in order to subsidize the Coastal Zone Management Program of Pará, this paper aims to identify, assess and classify natural and socio-economic vulnerabilities of this coastal zone by means of a Geographical Information Systems (GIS)-based composite coastal vulnerability index (CVI). In spite of the data problems and shortcomings, using ESRI’s Arcview 3.2 program, the CVI score, to classify, weight and combine a number of 16 separate natural and socio-economic variables to create a single indicator provides a reliable measure of differences (5 classes) among regions and communities that are exposed to similar ranges of hazards. The results are presented in three maps referred to as Natural, Socioeconomic and Total Vulnerability. The confidence associated with the results obtained, the need to utilize another variables, and to frequently update the ones used already were analyzed and discussed.     

Otolith analysis of juvenile walleye pollock Theragra chalcogramma from the western Gulf of Alaska

Growth rate and hatch date distributions were estimated for juvenile walleye pollock Theragra chalcogramma (Pallas, 1814) collected in autumn 1987 from the western Gulf of Alaska. Mean juvenile growth rates varied geographically by as much as 45%. A trend for slower growth around Unimak Pass and the Shumagin Islands and faster growth upstream in the Alaska Coastal Current towards Kodiak Island was noted; the fastest growth did not occur in the main habitat region. Juvenile hatch date distributions were compared to identify regional differences that might reflect stock structure. Juvenile hatch dates were compared with hatch dates of the same cohort sampled as larvae to test for selective mortality. Regional differences in hatch dates, along with other information, indicated several minor spawning populations located around Kodiak Island and near Unimak Pass. For the main aggregation of pollock in the Shumagin Island region, hatch date distributions were not significantly different among the early larval cohort sampled in late May, the late larvae sampled in mid-June to early July, and the juveniles sampled in autumn. Neither growth-rate nor size-dependent mortality of pollock between the larval and juvenile stages appears to be a dominant factor in determining survival patterns. An alternative test was attempted, by which lengths-at-age during larval life were back-calculated from juvenile otoliths and compared with lengths-at-age of the population sampled as larvae in May and June. Pollock surviving as juveniles in autumn were not larger as larvae than the general larval population. This result is an example of the observation that back-calculated lengths are almost always smaller than the lengths of fish sampled at age (Lee's phenomenon). Problems in determining survival patterns based on otolith back-calculations and comparison of hatch date distributions are discussed.     

Heavy-metal distribution and risk assessment of sediment and fish from El-Mex Bay, Alexandria, Egypt

Heavy metals are increasingly being released into natural waters from geological and anthropogenic sources. The distribution of several heavy metals (Cr, Cu, Cd, Pb, Zn, and Hg) was investigated in muscle, gill, and liver in two different fish species seasonally collected in El-Mex Bay (autumn 2004-summer 2005). In order to evaluate the pollution status of the Bay, the concentrations of the selected metals in the labile and total fractions were analysed in sediment samples collected from eight sites in El-Mex Bay during autumn 2004. Also, the Index of Geoaccumulation (I_geo) for the sediment was estimated. The total and labile fractions of the selected metals in sediment samples were 15.2 and 62.8 μg g^-1 dw for Cu, 1.8 and 5.0 μg g^-1 dw for Cd, 79.1 and 130.3 μg g^-1 dw for Zn, 0.2 and 1.2 μg g^-1 dw for Hg, 35.8 and 93.0 μg g^-1 dw for Pb, and 13.9 and 31.0 μg g^-1 dw for Cr. The concentrations of all metals were lower in flesh than those recorded in liver and gill due to their physiological roles. The metal pollution index for fish was calculated. Health hazard calculations for the contaminated sediments and fish consumption were calculated to evaluate the effect of pollution on health.     

Population differentiation of the Atlantic spotted dolphin (Stenella frontalis) in the western North Atlantic, including the Gulf of Mexico

Information about the genetic population structure of the Atlantic spotted dolphin [Stenella frontalis (G. Cuvier 1829)] in the western North Atlantic would greatly improve conservation and management of this species in USA waters. To this end, mitochondrial control region sequences and five nuclear microsatellite loci were used to test for genetic differentiation of Atlantic spotted dolphins in the western North Atlantic, including the Gulf of Mexico (n=199). Skin tissue samples were collected from 1994–2000. Significant heterozygote deficiencies in three microsatellite loci within samples collected off the eastern USA coast prompted investigation of a possible Wahlund effect, resulting in evidence for previously unsuspected population subdivision in this region. In subsequent analyses including three putative populations, two in the western North Atlantic (n=38, n=85) and one in the Gulf of Mexico (n=76), significant genetic differentiation was detected for both nuclear DNA (R _ST=0.096, P≤0.0001) and mitochondrial DNA (Φ _ST=0.215, P≤0.0001), as well as for all pair-wise population comparisons for both markers. This genetic evidence for population differentiation coupled to known biogeographic transition zones at Cape Hatteras, North Carolina and Cape Canaveral, Florida, USA, evidence of female philopatry, and preliminary support for significant genetic differences between previously documented morphotypes of Atlantic spotted dolphins in coastal and offshore waters all indicate that the biology and life history of this species is more complex than previously assumed. Assumptions of large, panmictic populations might not be accurate in other areas where S. frontalis is continuously distributed (e.g., eastern Atlantic), and could have a detrimental effect on long-term viability and maintenance of genetic diversity in this species in regions where incidental human-induced mortality occurs.

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Measurement of indoor radon concentration and assessment of doses in different districts of Alexandria city, Egypt

The main objective of this study is to assess the health hazard due to the indoor radon. Measurement studies have been carried out in 56 dwellings belonging to 14 residential areas in Alexandria city, Egypt. Results are obtained using the LR-115 (Type II) alpha track detector in “closed-can” geometry. The dosimeters were installed in bedroom, living room, and the kitchens of each house. For intercomparison purpose, dosimeters are installed in basements, ground floor, and first floor. Measured indoor radon concentrations were found to vary from 15 to 132 Bq m^?3. The average radon concentrations in living room, bedrooms, and kitchen in basements were found to vary from to be 39 ± 10, 63 ± 15 and 81 ± 25 Bq m^?3, respectively. In living room, bedrooms, and kitchen, on ground floor, the average radon concentrations were found to be 35 ± 9, 44 ± 6 and 56 ± 10 Bq m^?3, whereas on first floor, the average values are 29 ± 8, 34 ± 7 and 45 ± 8 Bq m^?3, respectively. The overall mean radon concentration in all surveyed districts has been found to be 44 ± 16 Bq m^?3. The mean annual estimated effective dose received by the residents of the studied area is estimated to be 0.75 mSv. The obtained results are compared with the indoor radon levels prescribed by the International Commission on Radiation Protection and are found to be less than the action level recommended.     

Biology of penaeid prawns in the Suez Canal lakes

A study was made from January 1988 to March 1989 of the penaid prawns in the Great Bitter Lake and Lake Timsah located in the central part of the Suez Canal. Two species of Red Sea origin were investigated,Metapenaeus stebbingi andTrachypenaeus curvirostris; the former is by far the commoner. Both species displayed seasonal breeding over the period April to October, with peaks in the early and late parts of the season.M. stebbingi had two main cohorts each year. A spring-spawned cohort survived 16 mo, and attained modal sizes of 23 mm carapare length (CL) for females and 16 to 17 mm CL for males. The autumn-spawned cohort survived 13 mo, and reached modal sizes of 20 mm and 15 mm CL for males and females, respectively. The reasons for the success ofM. stebbingi in the Canal lakes, in contrast to other Lessepsian penaeids which have flourished in the Mediterranean Sea, have been considered. The main factors are that it is essentially a shallow-water species, with excellent tolerance of salinity variations and adverse environments. However, the Canal lake populations have smaller maximum sizes, and mature earlier, than those in open seas.     

Generic framework for meso-scale assessment of climate change hazards in coastal environments

This paper presents a generic framework for assessing inherent climate change hazards in coastal environments through a combined coastal classification and hazard evaluation system. The framework is developed to be used at scales relevant for regional and national planning and aims to cover all coastal environments worldwide through a specially designed coastal classification system containing 113 generic coastal types. The framework provides information on the degree to which key climate change hazards are inherent in a particular coastal environment, and covers the hazards of ecosystem disruption, gradual inundation, salt water intrusion, erosion and flooding. The system includes a total of 565 individual hazard evaluations, each graduated into four different hazard levels based on a scientific literature review. The framework uses a simple assessment methodology with limited data and computing requirements, allowing for application in developing country settings. It is presented as a graphical tool—the Coastal Hazard Wheel—to ease its application for planning purposes.     

Forest structure of arid zone mangroves in relation to their physical and chemical environment in the western Gulf of Kachchh, Gujarat, Northwest coast of India

To understand natural and anthropic control of mangrove vegetation in the Gulf of Kachchh, a study was undertaken of its vegetation structure. Over 2 years (1999–2000) at three sites, mangrove vegetation was studied, including tree density, tree height, tree girth at breast height (GBH), canopy index, regeneration class and recruitment class, together with physico-chemical characteristics of water and sediment and the textural aspects of sediments. Reflecting the hot, arid hinterland of Gujarat, ambient temperatures and salinities are high in this macrotidal estuary, decreasing somewhat during the monsoon. The littoral soil supporting the mangrove is abundant in silty loam, silty clay and slity clay loam. The density of mature trees (Mangrove plants of GBH > 25 cm) ranged from 2088/ha to 3011/ha, the height of the trees ranged from 1.42 m to 9 m and the maximum mean GBH at all three sites was 33 cm, and the mean canopy indices ranged between 4.77 m² and 10.45 m². The maximum density of regeneration stages was 100,800/ha while that of recruitment stages was only 3,040/ha. While quite severely impacted by anthropic exploitation at one site, the mangrove ecosystem of Gulf of Kachchh was found to be mainly healthy and supporting associated organisms. The ecological and social role of the mangrove, and the potential for its future conservation are briefly discussed in the light of current legislation.     

Eco-Environmental benefit assessment of the western route in China's South-North Water Transfer Project

Assessing the benefits of China's South-North Water Transfer project (SNWT) requires successful integration of an analysis of economic and eco-environmental benefits (EEB). To attain such integration, it is necessary to assess the EEB in detail, after the economic benefits have also been thoroughly assessed. The shadow engineering and market value methods are the major EEB assessment methods used in this study. We have assessed the EEB of the forest and grassland ecosystems in the recipient regions of the Western Route Project (WRP) for 2020, 2030 and 2050. Finally, some proposals are also made for efficient and sustainable management of the WRP.     

Mitochondrial DNA variation in king mackerel (Scomberomorus cavalla) from the western Atlantic Ocean and Gulf of Mexico

King mackerel (Scomberomorus cavalla Cuvier) collected in 1992 and 1993 from 13 localities along the Atlantic coast of the southeastern USA and in the northern Gulf of Mexico were surveyed for variation in mitochondrial (mt)DNA and a nuclear-encoded dipeptidase locus (PEPA-2). Both polymorphic and fixed mtDNA restriction sites were identified and mapped using conventional and polymerase chain-reaction (PCR)-based methods. Heterogeneity in mtDNA haplotype frequencies was found only in comparisons of pooled haplotypes from Atlantic localities versus pooled haplotypes from Gulf localities. This finding indicates weak genetic divergence between king mackerel from the Atlantic and those from the Gulf. Frequencies of two PEPA-2 alleles essentially paralleled previous findings: one allele (PEPA-2a) was common among samples from western Gulf localities, whereas the other allele (PEPA-2b) was common among samples from Atlantic and eastern Gulf localities. There was considerable variation in PEPA-2 allele frequencies within broadly-defined regions. Variation in mtDNA haplotypes and PEPA-2 genotypes was independent, as was variation in mtDNA haplotypes with sex or age of individuals. Variation in PEPA-2 genotypes was not independent of sex or age of individuals. The latter result suggests that frequencies of PEPA-2 alleles in samples of king mackerel may stem, in part, from sex and age distributions of individuals within samples, and indicates that caution should be exercised in using allelic variation at PEPA-2 as a measure of population (stock) structure in king mackerel. The discordance in spatial patterning of mtDNA haplotypes versus PEPA-2 alleles across the Gulf (i.e. homogeneity in mtDNA haplotype frequencies versus heterogeneity in PEPA-2 allele frequencies) may be due to either female excess at several localities, sex-biased migration, or both. Observed patterns of genetic variation also are consistent with the hypothesis that king mackerel in the western Atlantic may have been subdivided during Pleistocene glaciation, and that the current distribution of PEPA-2 alleles may be a historical artefact. Received: 17 December 1996 / Accepted: 2 April 1997     

Mitochondrial gene variation in Mercenaria clam sibling species reveals a relict secondary contact zone in the western Gulf of Mexico

We investigated phylogeographic relationships among American Mercenaria taxa by assessing variation in a 444 nucleotide fragment of the mitochondrial 16S ribosomal gene in clams sampled from four representative sites in January to November 1994. Three of these sites were in the Gulf of Mexico, one was on the Atlantic coast in South Carolina. Direct sequencing of this amplified gene fragment in 85 individuals revealed 21 haplotypes. Phylogenetic analyses consistently resolved this variation into three well supported clades, and within-clade genetic divergence levels were markedly lower than among-clade values. One of the clades, A, was taxon-specific, in that it solely and exclusively contained specimens of M. mercenaria (Linnaeus, 1758) sampled in South Carolina. The other two clades, B and C, were the most divergent and both encompassed specimens of M. campechiensis (Gmelin, 1791) and of M. campechiensis texana (Dall, 1902), sampled from the three Gulf of Mexico sites. Clade B was found at high frequencies at all three Gulf sites, whereas Clade C occurred at low frequencies at two western Gulf sites. We interpret this pattern as resulting from the secondary contact and introgression of two allopatrically differentiated Mercenaria taxa in the western Gulf of Mexico. Clade C haplotypes may represent relict mitochondrial lineages from original Gulf Mercenaria spp. populations that predate massive mitochondrial introgression by M. campechiensis. We further propose that the M. campechiensis texana nuclear genome is a mosaic, heavily weighted toward M. campechiensis, but containing some relict alleles inherited from the precontact population, especially those governing shell characteristics, which may be adaptive in cohesive sediments of bays and estuaries in the northwestern Gulf of Mexico.     

Rapid assessment of postfire plant invasions in coniferous forests of the western United States.

Fire is a natural part of most forest ecosystems in the western United States, but its effects on nonnative plant invasion have only recently been studied. Also, forest managers are engaging in fuel reduction projects to lessen fire severity, often without considering potential negative ecological consequences such as nonnative plant species introductions. Increased availability of light, nutrients, and bare ground have all been associated with high-severity fires and fuel treatments and are known to aid in the establishment of nonnative plant species. We use vegetation and environmental data collected after wildfires at seven sites in coniferous forests in the western United States to study responses of nonnative plants to wildfire. We compared burned vs. unburned plots and plots treated with mechanical thinning and/or prescribed burning vs. untreated plots for nonnative plant species richness and cover and used correlation analyses to infer the effect of abiotic site conditions on invasibility. Wildfire was responsible for significant increases in nonnative species richness and cover, and a significant decrease in native cover. Mechanical thinning and prescribed fire fuel treatments were associated with significant changes in plant species composition at some sites. Treatment effects across sites were minimal and inconclusive due to significant site and site x treatment interaction effects caused by variation between sites including differences in treatment and fire severities and initial conditions (e.g., nonnative species sources). We used canonical correspondence analysis (CCA) to determine what combinations of environmental variables best explained patterns of nonnative plant species richness and cover. Variables related to fire severity, soil nutrients, and elevation explained most of the variation in species composition. Nonnative species were generally associated with sites with higher fire severity, elevation, percentage of bare ground, and lower soil nutrient levels and lower canopy cover. Early assessments of postfire stand conditions can guide rapid responses to nonnative plant invasions.     

Distribution,source apportionment and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in intertidal sediment of Asaluyeh,Persian Gulf

Surface sediment samples were collected from intertidal zone of Asaluyeh, Persian Gulf, to investigate distribution, sources and health risk of sixteen polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations ranged from 1.8 to 81.2 μg kg^?1 dry weight, which can be categorized as low level of pollution. Qualitative and quantitative assessments showed that PAHs originated from both petrogenic and pyrogenic sources with slight pyrogenic dominance. Source apportionment using principal component analysis indicated that the main sources of PAHs were fossil fuel combustion (33.59%), traffic-related PAHs (32.77%), biomass and coal combustion (18.54%) and petrogenic PAHs (9.31%). According to the results from the sediment quality guidelines, mean effects range-median quotient (M-ERM-Q) and benzo[a]pyrene toxic equivalents (BaP_eq), low negative ecological risks related to PAH compounds would occur in the intertidal zone of Asaluyeh. The total benzo[a]pyrene (BaP) toxic equivalent quotient (TEQ^carc) for carcinogenic compounds ranged from 0.01 to 7 μg kg^?1-BaP_eq, indicating low carcinogenic risk. The human health risk assessment of PAH compounds via ingestion and dermal pathways suggests low and moderate potential risk to human health, respectively.