author(s)
AM Houssou, E Montchowui and CA Bonou

abstract
Biodiversity particularly the micro-biodiversity of aquatic ecosystems in Africa, remains little known. This study aims to establish a first list of zooplankton species in Ouémé River basin and to assess population organization. Samples were taken monthly between October 2014 and September 2015 using a 20 μm mesh plankton net. The microscopic observation of samples allowed identification of 102 species including 84 rotifers, 11 copepods and 8 cladocerans. The Margalef index ranged from 6.58 in January to 10.53 in September. The temporal pattern of this index shown that in Ouémé River basin, the greatest zooplankton abundances do not necessarily coincide with the greatest specific riches. The Shannon diversity Index showed a good diversification of the population with values between 2.19 bit.ind^-1 in April and 3.65 bit.ind^-1 in July. However, the Evenness ranging between 0.09 and 0.47 showed the dominance of a relatively small species number on others. This dominance is assured by 27 species occupying 81.09% of the population (dominance Y = 0.81). Species such as: Brachionus plicatilis, Asplanchna priodonta, Brachionus caudatus, Anuraeopsis navicula were the most dominant in the Ouémé River basin. The study thus identified a rich zooplankton population which during low flow periods loses some of its diversification in favor of high abundance.