SPATIAL AND NYCTHEMERAL VARIATIONS OF ZOOPLANKTON IN URBAN AQUATIC ECOSYSTEMS OF DALOA (WEST-CENTRAL OF COTE DIVOIRE)

Urban aquatic ecosystems are important to many species. But they are more subject to urban anthropization which impacts the organisms living there. This study aims to determine the composition and zooplankton density of urban aquatic ecosystems in Daloa. Zooplankton were sampled in June and October 2020, by filtering 90 liters of water on a 50 µm mesh screen, from three fish ponds, three lakes, three streams and one pool. A total of 57 taxa, consisting of 29 Rotifers (50.88%), 17 Copepods (29.82%) and 11 Cladocerans (19.30%), were inventoried. The richness and density varied, depending on the ecosystems, respectively from 04 to 20 taxa and from 4.44 to 139.99 ind/L. These values were higher during the daytime than at night, and in October than in June. The highest taxonomic richness was obtained at ETPA pond (20 taxa), and the lowest at RUGO creek (04 taxa). The highest densities were obtained in the ponds (139.99 ind/L, 75.56 ind/L and 72.60 ind/L) and the lowest in the creeks (4.44 ind/L) and the pool (17.41 ind/L). Nauplii and copepodites and the cladoceran Alona sp. were most observed at night in the lakes. Redundancy analysis showed that the proliferation of some Rotifers and Copepods is optimal in relatively warm and alkaline water ecosystems. Although zooplankton richness is higher during the daytime, night-time sampling should not be overlooked as a way to expand zooplankton taxonomic databases.