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Abi-Ghanem C.,Center National des science Marines | Nakhle K.,Center National des science Marines | Khalaf G.,Center National des science Marines | Cossa D.,French Research Institute for Exploitation of the Sea
Archives of Environmental Contamination and Toxicology | Year: 2011

Mercury (Hg) contamination in coastal sediments has been widely studied in clay deposits; however, equivalent results on carbonated sediments are scarce. This article aims to study Hg distribution in Lebanese carbonate coastal marine sediments (Eastern Mediterranean) in order to characterize their contamination level and to explore the postdepositional mobility of methylmercury (MeHg) in the deposits. Vertical distribution profiles of total (HgT) and MeHg have been established for the solid phase of sediment cores collected in various near-shore environments chosen for their hypothetical various degrees of anthropization. In addition, dissolved MeHg was determined in sediment pore waters to test its mobility and potential availability for biota. Three sites on the Lebanese coasts - Akkar, Dora, and Selaata - were selected. Akkar is far from any direct contamination source, whereas Dora, located near the Beirut harbor, is a heavily urbanized and industrialized zone including a huge dump site, and Selaata is near a chemical plant that produces phosphate fertilizers. Particulate HgT concentrations in the sediments varied between <0.04 and 0.65 μg/g, with a proportion of MeHg lower than 1%. Based on a sediment quality guideline (MacDonald et al. 2000), we concluded that Dora bay sediments are heavily contaminated by Hg, with concentrations exceeding the "consensus-based threshold effect" level (0.17 μg/g) and almost reaching the "effects range-medium" level (0.71 μg/g). In spite of the low HgT concentration in Akkar and Selaata sediment (similar to natural carbonated sediment: 0.04 μg/g according to Turekian and Wedephol (1961), a closer analysis of the sediment core vertical profile allows one to observe an anthropogenic impact. This impact might be toxicologically insignificant; however, it allows tracing the time increase of Hg diffuse deposition. On the other hand, dissolved MeHg concentrations ranged from 0.04 to 0.09 and from 0.04 to 8.76 ng/l in the Selaata and the Dora sediments, respectively; MeHg vertical profiles in interstitial water enabled us to calculate diffusive fluxes of MeHg from the sediment varying from 0.3 to 1.0 ng/m2/day. Thus, the deposited sediments constitute a measurable source of bioavailable Hg for epibenthic organisms. © Springer Science+Business Media, LLC 2010. Source


Bacha M.,University of the Littoral Opal Coast | Jemaa S.,University of the Littoral Opal Coast | Jemaa S.,Center National des science Marines | Hamitouche A.,University of the Littoral Opal Coast | And 2 more authors.
ICES Journal of Marine Science | Year: 2014

Understanding the influence of oceanographic features on the structure of fish population is of basic importance to population dynamics studies and fisheries management. The European anchovy (Engraulis encrasicolus) exhibits a complex population structure which has produced conflicting results in previous genetic studies. This study examines the variability in the shape of the anchovy's otolith as a tool for identifying different stocks, and investigates the effects of oceanographic features on population structure. Anchovies were analysed from seven locations in the SW Mediterranean Sea and Atlantic Ocean along the northwestern African (Morocco) and Portuguese (Bay of Cadiz) coasts. A combination of otolith shape indices and elliptic Fourier descriptorswere investigated by multivariate statistical procedures. Within the studied area, three distinct anchovy stocks were identified: the Algero-Provenc¸al Basin, the southern Alboran Sea, and the Atlantic Ocean (Morocco and Gulf of Cadiz). The separation of the stockswas based on non-parametric discriminant analysis returning a classification percentage. Over 81% of the separation of the stocks could be explained by oceanographic features. Shape variability of anchovy otoliths was associated with the presence of the Almeria-Oran front, and the strait of Gibraltar. The Alboran stockwas distinct from the Algero-Provenc¸al Basin and from the closest Atlantic stocks (Gulf of Cadiz or Atlantic coast of Morocco). Results are discussed and compared with those previously obtained by genetic studies. This study supports the efficiency of otolith shape analysis for the stock identification of anchovy, and highlights the role of oceanographic features in stock separation. © International Council for the Exploration of the Sea 2014. All rights reserved. Source


Jemaa S.,University of the Littoral Opal Coast | Jemaa S.,Center National des science Marines | Bacha M.,University of the Littoral Opal Coast | Khalaf G.,Center National des science Marines | And 3 more authors.
Journal of Sea Research | Year: 2015

The European sardine, Sardina pilchardus, exhibits a complex population structure, which has produced conflicting results in previous genetic studies. Despite its importance in the fisheries industry, stock delineation for management and conservation purposes is still a matter of debate throughout the distribution range of the species. This study examines whether otolith shapes are more efficient than genetic markers to detect population structure in pelagic species with large population sizes. Sardines were analyzed from 15 sampling localities in the Northeast Atlantic and Mediterranean Sea covering almost the whole distribution range of the species. A combination of otolith shape indices and elliptic Fourier descriptors was investigated by multivariate statistical procedures. Within the studied area, three distinct groups were identified with an overall correct classification of 77%. Group A: northern Mediterranean Sea and Gulf of Gabès; group B: Atlantic Morocco-south Alboran-Algero-provençal coasts; and group C: European Atlantic coast. The Almeria-Oran front and the Gibraltar strait are not an efficient barrier for sardine population separation as there seems to be exchanges between populations of the south-western Mediterranean Sea and those of the Moroccan Atlantic Ocean coast or Gulf of Cadiz. The results are discussed in relation to environmental conditions, oceanographic features, and physical barriers to dispersal in the study area, and compared with those obtained by previous genetic, morphometric, and meristic data. For pelagic species with high gene flow, present results highlighted the need to take into account the identification of phenotypic stocks to ensure sustainable fishery benefits and efficient conservation as they may have unique demographic properties and responses to exploitation. © 2014 Elsevier B.V. Source


Jemaa S.,University of the Littoral Opal Coast | Jemaa S.,Center National des science Marines | Bacha M.,University of the Littoral Opal Coast | Khalaf G.,Center National des science Marines | Amara R.,University of the Littoral Opal Coast
Fisheries Research | Year: 2015

The European anchovy, Engraulis encrasicolus, is one of the most commercially relevant fisheries resources in many countries bordering the northeast Atlantic coasts and the Mediterranean Sea. However most of its fishery stocks are currently fully exploited or overexploited and understanding its population structure is necessary for designing appropriate management regulations in fisheries. Investigation of otolith shape analysis from 15 localities across most of the anchovy range distribution revealed a complex population structure. Four distinct groups of anchovy were identified with an overall correct classification of 83%. Group A: North Sea and English Channel; group B: Mauritania and southeast Atlantic Morocco; group C: northeast Atlantic Morocco-Gulf of Cadiz-south Alboran-Algero-Provençal coasts; and group D: northern Mediterranean Sea. However, at smaller spatial scales, more complex population structure was hypothesized in the Mediterranean Sea, mainly in relation to oceanographic features. The results support the usefulness of otolith shape analysis for population structure analysis both at larger and smaller spatial scales where genetic studies generally fail to discriminate between local groups of fish. From a management perspective, these local and isolated groups of fish may have unique demographic properties and should be managed separately since they may react independently to exploitation. © 2015 Elsevier B.V. Source

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