DISTRIBUTION OF DINOCYSTS IN THE SURFACE SEDIMENTS OF SIDI MOUSSA LAGOON : (ATLANTIC COAST-MOROCCO)

Abstract. The Sidi Moussa lagoon, (32°52′0″ N / 8° 51′05″ W) is located on the Moroccan Atlantic coast between the cities of El Jadida and Safi about 15 km South of the Jorf Lasfar industrial complex, The climate of the lagoon is classified as hot temperate. It is characterised by an oceanic influence. This study of dinoflagellate cyst mapping is the first of its kind from the Sidi Moussa lagoon. the objectives of the present survey were (i) to evaluate to the spatial variation of dinoflagellate cyst assemblages in the sediment along the Sidi Moussa lagoon (ii) to assess the densities of its cysts (iii) to compare the cyst assemblages in this study with that of other sites. The data were collected in a scientific campaign by zodiac carried out from in April 2018 by core following a sampling network of 21 stations distributed randomly in the study area. The surface layer of the sediment cores (3 cm) was sliced and kept at 4° C until analysis. The highest total cyst abundance was 194 cysts. g⁻¹ dry sediment. The Pearson statistical test revealed a positive and significant correlation between cyst abundance and water content, organic matter and of fine sediment. Our study showed the presence of morphotypes of potentially toxic species. The cysts of these species present in the sediment of the Sidi Moussa lagoon could germinate, when environmental conditions become favorable, and in turn could inoculate the water column with the subsequent bloom formation. This study confirms the usefulness of cyst analysis in the assessment of harmful bloom risk in this area important for oyster’s culture.