Seasonal distribution of zooplankton in the Aby-Tendo-Ehy lagoons system (Côte d’Ivoire, West Africa)

Abstract

Zooplankton is essential components of aquatic ecosystem where it contributes to transferring energy and organic matter from the primary producers to the higher trophic level taxa. However, changes in some environmental characteristics strongly influence their diversity and abundance. This work aimed at determining the spatial and seasonal distributions of zooplanktonic fauna in relation to some physico-chemical parameters in the Aby-Tendo-Ehy lagoons system. Zooplankton samples were collected monthly from March 2012 to February 2013 in six sampling sites with a cylindro-conical net of 64 μm in mesh opening size. Sampling observation showed of 53 taxa including Rotifera, Copepoda and Cladoceran. Rotifera was the most abundant group (83% of total abundance). Overall taxa diversity increased from Aby lagoon (n = 46) to Ehy lagoon (n = 50). The total abundance of zooplankton increased from Aby lagoon (mean = 122.8 ind/l) to Ehy lagoon (mean = 167.4 ind/l). Zooplankton abundance in Tendo and Ehy lagoons were dominated by freshwater taxa (Lecane leontina) while in Aby lagoon this parameter was dominated by brackish water taxa (Brachionus plicatilis). This study revealed that, in Aby lagoon, zooplankton was influenced mainly by salinity, transparency, dissolved oxygen and conductivity. However, in Ehy lagoon zooplankton was influenced by temperature and pH during the dry season. In Tendo lagoon, main factors are depth during the dry season and pH and temperature during the rainy season.
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Keywords: Zooplankton, abundance, community distribution, environmental variables, Aby-Tendo-Ehy lagoons, Côte d’Ivoire