Potentially harmful microalgae in coastal waters of the Algiers area (Southern Mediterranean Sea)

18 pages,16 figures, 3 tablesA series of seasonal, monthly and short-term samplings was conducted in open and confined waters of the Algiers area in 2001-2002 and summer 2003 in order to detect potentially harmful microalgae species (HAB). A total of 14 potentially toxic and 18 bloom-forming species were recorded, of which some were found for the first time in Algerian coastal waters: the potential toxin producers Alexandrium minutum, Dinophysis sacculus (dinoflagellates) and Pseudo-nitzschia calliantha (diatom), as well as the bloom-forming species Lepidodinium chlorophorum (dinoflagellate), Cyclotella meneghiniana (diatom) and Holococcolithophora sphaeroidea (holococcolithophorid). The latter produced a very important bloom with considerable water discoulouration. The occurrence and duration of this event in the Algiers Harbour underline the importance of this enclosed structure as a growth area for HAB species. The transport of a H. sphaeroidea bloom toward off-shore waters by an anticyclonic eddy demonstrates the effect of Algerian current mesoscale instabilities on the spatial distribution of phytoplankton communities.H. Illoul was supported by a grant of the Agencia Española de Cooperación Internacional (AECI-MAE) and the Conselleria de medi ambient, Govern de les Illes Balears and CSIC through the contract " Evaluación y monotorización de la calidad de las aguas costeras de las Islas Baleares. The authors wish to thank L. Arin, D. Blasco, M. Estrada, E. Garcès, S. Quijano, N. Sampedro, M. Vila ( ICM,CSIC, Barcelona ), S.Fraga (IEO, Vigo), F.L. Samson-Kechacha (USTHB, Algiers) for help and useful suggestions. Also A. Mamache and the ship crews of R/V "ibtacim, Baba Arroudj" and M.S. Ben,Yahia during the research cruises.Peer reviewe