Variations spatio-temporelles de l’abondance des nauplii de copépodes dans les lagunes côtières tropicales en relation avec les variables environnementales: cas des lagunes de la Côte d’Ivoire

Abstract

Copepod nauplii are abundant in aquatic environments in tropical areas and have interesting biochemical and physical characteristics that make them a good alternative and/or supplemental food for fish larvae. All environmental factors governing their variation can have an impact on the reproductive success and development of fish larvae. The main aim of this work is to determine the spatio-temporal variations in the abundance of copepod nauplii in the lagoon environments of Côte d’Ivoire in relation to the physico-chemical parameters of these brackish ecosystems in order to identify their determinism. This study shows that the abundance of nauplii varies significantly during the seasons, with mean values in the dry season (12–98 ind.l-1) higher than in the wet season (9–88 ind.l-1). Our results also show that in the Grand-Lahou and Fresco lagoons, the lowest abundances were recorded in the communication zone between the lagoon and the sea (channel) in all seasons. The study of the correlation between physico-chemical parameters and the abundance of nauplii of copepods shows that the abundance of nauplii increases with temperature, conductivity, dissolved oxygen, nitrite, and ammonium with a significantly positive correlation (Rs: 0.21–0.94 and p < 0.001). On the other hand, nauplii abundance shows a non-significant and negative correlation with turbidity and pH in all study media (Rs: -0.03 to -0.62 and p > 0.05).