The Oualidia Lagoon is a semi enclosed marine ecosystem connected to the Atlantic Ocean of Morocco and exposed to human activities, mainly agriculture and oyster farming. The present study aims to characterize the spatio-temporal variation of the phytoplankton assemblage and to highlight the effect of the main environmental parameters on this important planktonic component evolving in a vulnerable anthropized ecosystem. For this purpose, a field survey was carried out during four seasons in 2011 to determine the biotic (phytoplankton, chlorophyll a) and abiotic (temperature, salinity and nutrients) variables during low and high tide periods. Results highlight an established spatial variation of physicochemical parameters especially at low tide, with contrasted environmental conditions between the upstream and downstream zones. The phytoplankton diversity and abundance were characterized by a pronounced seasonal pattern. The Oualidia Lagoon is a nutrient rich ecosystem, especially in its upstream part. We also showed that both planktonic diversity and abundance were maximum in autumn and summer. The phytoplankton richness is governed by two main factors: the seasonality of nutrient enrichment and the regular supply of Atlantic seawater. Nitrate and ammonium were the main environmental abiotic factors determining the development of phytoplankton populations. The dynamic of phytoplankton in the Oualidia Lagoon is highly influenced by marine waters incoming from the Atlantic Ocean especially during the upwelling season. Finally, potential harmful algal species belonging to different genera such as Pseudo-nitzschia, Alexandrium, Prorocentrum, Dinophysis, Ostreopsis, Karenia, Coolia, Gonyaulax, Gymnodinium, Dictyocha and Chattonella were encountered showing a potential in this ecosystem to develop noxious blooms.Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. Highlights► The spatio-temporal variation of phytoplankton assemblage (biodiversity and abundance) was driven by environmental constraints from both land and sea. ► The taxonomic richness was dominated by typical marine species. ► The inventoried taxa were dominated by diatoms and dinoflagellates when considering both species number and density. ► Potential Harmful Algal Blooms species, belonging to different genera such as Pseudo-nitzschia, Alexandrium, Prorocentrum, Dinophysis, Ostreopsis, Karenia, Coolia, Gonyaulax, Gymnodinium, Dictyocha and Chattonella were encountered. ► The warm season (August and October) showed the highest values of phytoplankton species diversity and densities particularly upstream.

-This comparative study of mesozooplankton communities in the Tangier (Atlantic) and M'Diq (Mediterranean) regions was carried out in March, May and December 2006 and in May, July and November 2007. In both sectors, the zooplankton is mainly dominated by copepods, which represent 93% in Tangier and 87% in M'Diq, with respectively 85 species in 24 families and 81 divided into 22 families. Spatio-temporal analysis of Copepod specific richness data revealed highest values occurring in both areas during December 2006 and November 2007 with 36 and 30 species respectively. During other seasons, specific richness did not generally exceed 25 species. However, irrespective of area, the composition of the Copepoda population was usually dominated by Paracalanus parvus and Oncaea venusta. In terms of total density, the Atlantic is greater than the Mediterranean sector with a maximum density of 1093 ind.m −3 and 796 ind.m −3 , respectively, recorded in July and May, 2007. The Shannon diversity index was calculated and indicated that the Copepod community is more stable and balanced in the Tangier region compared to the M'Diq area, and in 2007 compared to 2006. Moreover, seasonal variation is more marked in the Atlantic than in the Mediterranean area and in both sectors, the autumn season is characterized by a low productivity but high specific diversity. Key words

phytoplancton marin a e ´te ´e ´tudie ´en janvier et juillet 2002 au niveau de quatre radiales dispose ´es aux latitudes 32830 0 N, 298N, 24830 0 N et 248N, sur la co ˆte atlantique marocaine. Le nombre total d'espe `ces recense ´es dans cette zone s'e ´le `ve a `142 taxons. La richesse spe ´cifique maximale aussi bien en hiver qu'en e ´te ´a e ´te ´enregistre ´e aux environs de Dakhla (248N). La variabilite ´spatio-temporelle de la structure des peuplements dans chaque radiale a montre ´que les peuplements co ˆtiers sont les plus structure ´s et riches en espe `ces. La variation verticale de la richesse et de la diversite ´spe ´cifique a re ´ve ´le ´une homoge ´ne ´ite éntre les diffe ´rents niveaux bathyme ´triques. En termes de densite ´, le sud est plus productif que le nord de la zone d'e ´tude ; cela est du ˆa `la pre ´sence quasi permanente de l'upwelling au sud de l'Atlantique marocain. La distribution bathyme ´trique des densite ´s a e ´te ´plus he ´te ´roge `ne pendant la saison chaude, caracte ´rise ´e par une activite ´d'upwelling plus intense qu'en saison froide. Les espe `ces Thalassionema nitzschioides, Asterionellopsis glacialis, Melosira, Chaetoceros et Leptocylindrus minimus constituent des indicateurs des courants ascendants froids « Upwellings ».ß 2012 Acade ´mie des sciences. Publie ´par Elsevier Masson SAS. Tous droits re ´serve ´s.

The present study aimed to assess the composition, abundance and diversity of phytoplankton assemblage along the Moroccan Mediterranean Coast. Phytoplankton samples were collected in October 2018 at 48 stations from M’diq bay in the West to Saïdia in the East. 92 taxa have been inventoried, belonging to five groups. Diatoms dominate qualitatively and quantitatively (85.5%), followed by dinoflagellates (12%). Phytoplanktonic diversity and abundance was pronounced in the western part of Moroccan Mediterranean Sea, especially (from Jebha to M’diq) because of the influence of the Atlantic flow.

This overview sums up the results of main investigations and knowledge about zooplankton off Moroccan Atlantic coast. Copepods diversity, spatial distribution, seasonal variability and hydrology off Moroccan Atlantic coast are given. A compilation of taxonomic list of copepods' species found therein was established from published studies, they accounted for 210. Diversity and richness varied strongly between seasons, an onshore offshore gradient was observed as well. Species composition differed from northern to southern Moroccan Atlantic coast although most dominant species off Morocco's coasts were Calanus helgolandicus, Paracalanus parvus, Acartia clausi and Corycaeus typicus. In addition, the largest number of species was found in upwelling regions. A synthesis study was established in order to spatial distribution of copepods along Moroccan Atlantic coast. The Factorial Correspondence Analysis of copepod species characterizing the most important sectors has shown different patterns of copepods distribution across Moroccan Atlantic coast; three main areas were clearly segregated according to their taxonomic composition (Northern, Central and Southern Atlantic).