Assessment of Plankton and Benthos Distribution of the Lower River Benue, Ibi Axis, Taraba State, Nigeria

A four month research work was carried out to assess the distribution, abundance; diversity of plankton and benthos in the Lower River Benue at the Ibi axis, Taraba State. The objectives of the study was to identify the plankton and benthos, to assess the composition of the plankton and benthos, and to assess the abundance and diversity of the plankton and benthos species of the Lower River Benue, Ibi axis, in order to evaluate the ecological status of the river and determine the influence of physicochemical parameters on the aquatic organisms. Plankton net and van veen grab sampler were used to sample the three stations (A, B, and C), followed by laboratory identification, classification and enumeration using standard procedures, while water temperature, power of Hydrogen, dissolved oxygen, turbidity, electrical conductivity, total dissolved solid were measured in-situ. Results showed a total number of 32 individual species were identified from 755 harvested species, comprising of 350 phytoplankton (46.36%), 276 zooplankton (36.56%), and 138 benthos (18.28%). The phytoplankton species consist of 15 individual species belonging to 15 families and 13 orders, dominated by Euglenales, Naviculales, Bacillariales, and Chroococcales, the most species were Euglena gracilis and Navicula cuspidata. Zooplankton species were represented by 10 individual species, 8 families and 5 orders, mainly Cladocera, Copepoda, Rotifera, and Protozoa, with Daphnia pulex as the dominant species. The benthic macro-invertebrate assemblage comprised of 7 individual species, 7 families and 7 orders, including Diptera, Oligochaeta, Tricladida, and Amphipoda, with Anopheles larvae, Dugesia sp., and Gammarus roeseli being prominent. Margalef species richness indices indicated moderate biodiversity across the sampled stations, while physicochemical parameters showed no significant spatial variation and remained within ranges suitable for aquatic life, suggesting that the Lower River Benue at the Ibi axis is a moderately productive freshwater ecosystem capable of supporting diverse plankton and benthic species, hence, it is recommended that there is a need for continuous monitoring and regulation of anthropogenic activities to ensure sustainable management and conservation of the river’s aquatic resources.