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Objectifs: Cette etude vise a determiner la distribution spatio temporelle du zooplancton en relation avec les caracteristiques environnementales dans quatre rivieres cotieres du Sud-est de la Cote d’Ivoire. Methode et resultats: Le zooplancton a ete echantillonne mensuellement de mars 2012 a fevrier 2013 a l’aide d’un filet a plancton de 64 Gm de vide de maille. Au total 28 taxons ont ete observes (15 Rotiferes, 6 Copepodes, 4 Cladoceres et 3 autres organismes). Les Rotiferes constituent le groupe dominant avec 67% de l’abondance totale. Rotaria sp. est le taxon le plus abondant (52%). Globalement, la richesse taxonomique et l’abondance les plus faibles ont ete enregistrees dans les rivieres recevant les effluents d’unite agroindustrielles de palmier a huile (Ehania, Boulo1). Les resultats de l’analyse de redondance (RDA) montrent que les variables Influencant fortement la diversite taxonomique et l’abondance sont la vitesse du courant, la conductivite, la temperature, le taux de fermeture de la canopee et la proportion des debris vegetaux. Conclusion et application: Cette etude a permis de determiner l’influence des variables environnementales sur la distribution du zooplancton dans 4 rivieres cotieres du Sud-est de la Cote d’Ivoire et confirme la possibilite d’utiliser Rotaria sp. comme indicateur de pollution. Mots cles: Zooplancton, diversite, abondance, effluents industriels English Title: Distribution of zooplankton in relation with environmental characteristics of four coastal rivers in South-Eastern Cote d’Ivoire (West Africa) English Abstract Objectives: This study aims to determine the distribution of zooplankton in relation with environmental variables in four coastal rivers in South East Cote d’Ivoire. Method and results: Zooplankton samples were collected monthly from March 2012 to February 2013 in six sampling sites with a cylindro-conical net of 64-Gm mesh-size. 28 taxa of zooplankton belonging to Rotifera (15 taxa), Copepoda (6 taxa), Cladoceran (4 taxa) and others zooplankton (3) were identified. Rotifers constituted the most abundant group (67%). Rotaria sp. was the most abundant taxa (52% of total abundance). Overall, taxa diversity and abundance were lower in rivers receiving palm oil mill effluents in their catchment area. The ReDundancy Analysis (RDA) performed showed that environmental variables such as current velocity, conductivity, water temperature, canopy closure and vegetal debris occurrence influence strongly diversity and abundance of zooplankton. Conclusion and application: This study allowed to identify environmental factors, which influence the distribution of zooplankton taxa and show the possibility to use Rotaria sp. as pollution indicator. Keywords: Zooplankton, diversity, abundance, industrial effluents |
