Résumé:
Phytoplankton biodiversity is the basis of the functioning of the aquatic ecosystems. Also,
understanding and evaluating the effects of the change in our environment and their impact
on planktonic populations is an important element. In fact, this paper was to appreciate the
diversity and composition of phytoplankton in relation to some physicochemical parameters.
Water samples were collected along the Algerian coastline (Alboran Sea, the Algerian
basin and the Middle area), during the period May-June 2013. The study area contained a
diversified phytoplankton community (296 species), belonging to 138 genera. The algal
groups were represented and classified as dinoflagellates (180 species), diatoms (103
species), cyanophyceae, coccolithophorids, euglenids, and chrysophytes (13 species). The
spatial distribution of cell densities revealed a heterogeneous phytoplankton composition
dominated by dinoflagellates, which represent 63% of the total abundance, followed by diatoms
(35%). Quantitatively, we observed a highest cell density and diatoms abundance in
most stations of the Alboran Sea decreasing towards the east (Algerian basin). The peak of
dinoflagellates in June was represented by Prorocentrum and Gymnodinium genera.
