THE ZOOPLANKTON OF OSSE RIVER, EDO STATE

ABSTRACT

Zooplankton are very sensitive to environmental modifications and are important indicators for evaluating the status of aquatic ecosystems. This study was carried out at three sites along the stretch of Osse River, Edo State, Nigeria from July to September 2021 to determine the zooplankton community structure. Data were statistically examined using the Non-parametric test. Among the physical and chemical parameters studied, only water temperature showed significant spatial variation (P<0.001), the others did not (P>0.05). A total of 10 species of zooplankton were encountered. They include 7 Cladocera, 1 Copepoda, and 2 Rotifera. Cladocera accounted for 57.57% of the total number of zooplankton recorded, while the Copepoda and Rotifera contributed 35.71% and 10.71% respectively. Daphniidae was the dominant family of Cladocera, while Cyclopidae and Gastropidae were the most dominant Copepoda and Rotifera recorded respectively. The overall spatial abundance of zooplankton showed no significant variation (P>0.05). The general diversity using Shannon Wiener and Margalef’s indices showed higher diversity in the increasing order of stations 1<2<3. Similarity tests using Jaccard indices showed similarity across all three stations, while Bray- Curtis indices showed a complete dissimilarity from station 3. All correlation analyses proved significant at a 95% confidence level (r_{0.05 (2)7}=0.666). The study revealed that season affect the composition and distribution of zooplankton.