Phytoplankton distribution in the upwelling areas of the Moroccan Atlantic coast localized between 32 super( degree )30 super(′ )N et 24 super( degree )N

• Published in: Comptes rendus. Biologies Vol. 335; no. 8; pp. 541 - 554
• Main Authors: Elghrib, Hasna, Somoue, Laila, Elkhiati, Najat, Berraho, Amina, Salah, Siham, Ettahiri, Omar
• Format: Journal Article
• Language: French
• Published: 01.01.2012
• Subjects: Marine
• ISSN: 1631-0691
• DOI: 10.1016/j.crvi.2012.07.002

Marine phytoplankton was studied in January and July 2002 along of four transects. A total of 142 taxa were recorded in this area. The maximal specific richness, both in summer and in winter, was registered around Dakhla. The global spatiotemporal variability of species richness and specific diversity showed that the most structured and species-rich populations are situated in the coastal areas. The vertical variation of the two parameters showed homogeneity between depth levels. The maximal phytoplanktonic densities are recorded in the southern transects due to the permanent upwelling activity in the southern Atlantic coast. The bathymetric distribution of densities was more heterogeneous during summer, characterized by a high intensity of upwelling. The species Thalassionema nitzschioides, Asterionellopsis glacialis, Melosira, Chaetoceros and Leptocylindrus minimus are indicators of upwelling.Original Abstract: Le phytoplancton marin a ete etudie en janvier et juillet 2002 au niveau de quatre radiales disposees sur la cote atlantique marocaine. Le nombre total d'especes recensees dans cette zone s'eleve a 142 taxons. La richesse specifique maximale aussi bien en hiver qu'en ete a ete enregistree aux environs de Dakhla . La variabilite spatio-temporelle de la structure des peuplements dans chaque radiale a montre que les peuplements cotiers sont les plus structures et riches en especes. La variation verticale de la richesse et de la diversite specifique a revele une homogeneite entre les differents niveaux bathymetriques. En termes de densite, le sud est plus productif que le nord de la zone d'etude ; cela est du a la presence quasi permanente de l'upwelling au sud de l'Atlantique marocain. La distribution bathymetrique des densites a ete plus heterogene pendant la saison chaude, caracterisee par une activite d'upwelling plus intense qu'en saison froide. Les especes Thalassionema nitzschioides, Asterionellopsis glacialis, Melosira, Chaetoceros et Leptocylindrus minimus constituent des indicateurs des courants ascendants froids < Upwellings >.