Spatiotemporal variability of phytoplankton in the Aglou-Sidi Ifni coastline (Moroccan Atlantic Coast)

ABSTRACT This study was carried out between April 2014 and March 2016. We counted 233 species dominated by diatoms (126 species) and dinoflagellates (97 species). The most common diatom species were Leptocylindrus danicus and Rhizosolenia styliformus, while Scrippsiella sp. was the most common dinoflagellate species. The richness and relative abundance of diatoms were greater during the spring of 2014–2015 and the winter of 2015 and present an increasing north–south gradient. However, those of dinoflagellates were greater during the summer and autumn seasons of the years 2014–2015 and the winter of 2016, with a decreasing north–south gradient. This could be mainly related to the difference between the requirements of these two groups and the spatiotemporal variability of the physicochemical characteristics of the waters governed by seasonal and inter-annual variations of the currents, by the floods and by the morphology of the coast in this area. Indeed, the increase in the richness and abundance of dinoflagellates coincides with the increase in temperature, transparency and the decrease in the concentration of nutrient salts in the environment. However, the increase in nutrient content, the decrease in temperature and transparency favours diatoms compared with dinoflagellates.