Chlaida, M., Laurent, V., Kifani, S., Benazzou, T., Jaziri, H., and Planes, S. 2009. Evidence of a genetic cline for Sardina pilchardus along the Northwest African coast. – ICES Journal of Marine Science, 66: 264–271. In all, 700 Sardina pilchardus from 14 locations throughout the Atlantic and Mediterranean Moroccan coastlines were screened for eight enzymatic loci that show polymorphism. Analysis of allelic frequencies showed a genetic break in the area of the Bay of Agadir, segregating two groups of samples, confirmed by analysis of molecular variance; a first consisting of Sidi Ifni (29°12′N) and southern samples down to the southern limit of the species in Mauritania (19°03′N 16°28′W), and a second starting in the Bay of Agadir (30°48′N) and consisting of northern samples that appeared homogeneous with the Mediterranean samples. Specifically, a survey of the SOD* loci demonstrated a genetic cline in allelic frequencies along the coastline. Using a clinal variation model under a state of equilibrium, we estimate a dispersal rate of 189 ± 52 km per generation between Mauritania and Ras Kebdana. This major break towards the south of the Bay of Agadir offers a new perspective on the management of sardine, which ideally ought now to be managed as two stocks along the Moroccan coast. The break is most likely induced by hydrodynamic influences that virtually isolate southern from northern populations.
Les eaux de l'Oued Hassar (Maroc) sont caractérisées par une forte minéralisation. La conductivité, variant entre 3470 et 7210 µS.cm-1, est due essentiellement aux fortes teneurs en chlorures. L'examen de l'Indice de Pollution Organique (IPO) montre que l'effluent d'eaux usées provenant de la ville de Mediouna constitue la principale source de pollution des eaux de l'Oued Hassar.
Concernant l'étude des diatomées épilithiques, 61 espèces et variétés de diatomées ont été inventoriées. Ces taxons sont liés particulièrement à la salinité (Pleurosira laevis, Fragilaria pulchella,…) et à la charge organique (Nitzschia palea, Gomphonema parvulum,…).
Quatre indices diatomiques ont été testés pour l'évaluation de la qualité des eaux de l'Oued Hassar : l'Indice Diatomique Pratique (IDP), l'Indice Diatomique Générique (IDG), l'Indice de Sládecek (SLA) et l'Indice Diatomique Trophique (IDT). La variation spatio-temporelle de ces indices reflète bien la dégradation de la qualité de ce cours d'eau, particulièrement en aval du rejet de la ville de Mediouna (IDP=3,86 ± 1,84 ; IDG=6,05 ± 1,95 ; SLA=4,35 ± 1,93 ; IDT=5,80 ± 1,31). Parmi ces indices testés, seul l'IDP présente une corrélation significative (0,63 ; α<5%) avec l'IPO (indice de référence) tandis que l'IDG, le SLA et l'IDT montrent des corrélations non significatives avec cet indice (0,38 ; 0,27 et -0,11 respectivement).
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