Zooplankton constitutes a sensitive tool for monitoring environmental changes in coastal lagoons; however, the available information on zooplankton communities is not sufficient to optimize their rational management. The relationships between zooplankton distribution and environmental factors were studied in a tropical lagoon to test whether the indicator properties of zooplankton assemblages could be used to monitor water quality, in a context of expected eutrophication provoked by an increasing anthropogenic activity. Twenty-one (21) stations were sampled monthly from January to December 2004. The community was composed of 65 taxa including Copepoda, Rotifera, and Cladocera. Copepoda was the most abundant group (81% of total numbers). The main zooplankton species were Oithona brevicornis, Acartia clausi, and Brachionus plicatilis. The highest zooplankton abundance (171-175 ind. l -1 ) was recorded during the long, dry season (February-April) and the lowest (40-45 ind. l -1 ) during the rainy and the flood periods (June-July). At a spatial level, the lowest abundance was observed in the estuarine zone. During the dry seasons (December-April and AugustSeptember), marine zooplankton taxa were abundant near the channel of Grand-Lahou, and brackish water taxa dominated in the other sites. Multivariate analyses (Co-inertia) showed that the composition of zooplanktonic communities and their spatio-temporal variations were mainly controlled by salinity variations closely linked to the climatic and hydrological context. The role of the trophic state on zooplankton communities could not be clearly evidenced. Our results and a comparison with previous studies in the neighboring, highly polluted Ebrié Lagoon suggest that the ratio between Oithona and Acartia abundance could be used as biological indicator for the water quality.

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.

Distribution du zooplancton en relation avec les caractéristiques environnementales de quatre rivières côtières du Sud-est de la Côte d'Ivoire 9344 Distribution du zooplancton en relation avec les caractéristiques environnementales de quatre rivières côtières du Sud-est de la Côte d'Ivoire (Afrique de l'ouest).