Spatio-Temporal Variation of Dinoflagellates of the Genera <i>Ceratium</i> (Schrank 1793) and <i>Protoperidinium</i> (Bergh 1881) in Relationship with Some Abiotic Variables in the Atlantic Coast of Kribi (South Region—Cameroon)

Abstract

A study to list Dinoflagellates species belonging to the genera Ceratium and Protoperidinium and some abiotic factors associated with them was carried out in the Kribi coast from February 2020 to February 2021 following a monthly sampling frequency. For the inventory, 60 L of water including 20 L on the surface, 20 L in the trophogen layer and 20 L in the tropholytic layer were filtered through a sieve of 20 μm and the retentate obtained was fixed whith lugol for identification and counting operations using an Olympus microscope. The morphotypes of the taxa were filmed using an Omax Toupvix eye camera. Physico-chemical results showed very good water oxygenation (89.35%), low Suspended Solid concentration (6.36 ± 4.71 mg/L), basic pH (8.53 ± 0.4 U.C), average salinity of 15.87 ± 3.1 g/L and conductivity around 26.73 ± 4.96 mS/cm. The average water temperature hovered around 29.51°C ± 1.28°C. The average values of nitrates and orthophosphates showed a progressive enrichment of the waters of the studied section with nitrate (1.52 ± 0.87 mg/L) and orthophosphate (1.84 ± 3.98 mg/L). This work allowed to identify 17 species of the genera Ceratium and 22 of Protoperidinium. The genera Protoperidinium was the most diverse while it was the taxa belonging to the genera Ceratium that had the highest densities. Ceratium furca was the only spatially and seasonally regular species with occurrence frequencies of 75.31% and 79.16% respectively. According to similar studies, 06 species reconized harmful were inventoried during this study. These are Ceratium furca, Ceratium fusus, Ceratium tripos, Protoperidinium divergens, Protoperidinium steinii, Protoperidinium crassipes. Temperature and oxygen are the abiotic factors that showed more affinities with the taxa inventoried in view of the significant correlations obtained. With a view to preventing blooms on the Cameroonian Atlantic coast, regular monitoring of the harmful species identified is desirable.