Seasonal characterization of the nutrients state in Oualidia Lagoon (Moroccan Atlantic coast)

The nutrient cycle in Oualidia lagoon, on the Atlantic Moroccan coast, was studied at both spatial and temporal scales, covering spring and summer conditions. Water samples were collected bimonthly at high tide from March to August during years 2011 and 2012 at six stations distributed throughout the lagoon. The physico- chemistry (temperature, salinity, dissolved O2) and nutrient enrichment of the lagoon surface water were monitored. The average nutrient concentration of surface water were 14.4 μmol.l-1 and 28.1 μmol.l-1 for NH4+, 20.4 μmol.l-1 and 19.9 μmol.l-1 for PO43- and 3.7 μmol.l-1 and 7.6 μmol.l-1 for NO2- in 2011 and 2012, respectively. Strong seasonal differences of nutrient distribution at the different stations were noticed. Temperature, salinity and dissolved O2 were correlated with nutrient concentrations, all parameters showing low spatial (inter-station) variability. Hydrological conditions exert a major control on the nutrient cycling in the lagoon. Results of this study are important to increase the richness on the scientific knowledge of nutrient dynamics along the Moroccan Atlantic coast, particularly in the semi-enclosed lagoons that are important transitional systems.