Macroinvertebrates of Wupa River, Abuja, Nigeria: Do environmental variables pattern their assemblages?

Abstract

Macroinvertebrates, alongside physico-chemical variables, were sampled and analyzed for nine months between April and December 2019 in three Stations (Stations 1, 2 and 3) in the Wupa River, Abuja, Nigeria. The stations were selected to represent an increasing pollution gradient from Station 1 < Station 2 < Station 3. Our result showed that Station 1 had the lowest mean values of physico-chemical variables, except conductivity and DO. Except for temperature (26.83±0.33 o C), BOD (13.05±0.77 mg/l) and pH (6.91-7.80) that were highest in Station 2, all other physico-chemical variables had their highest mean values in Station 3. The principal component analysis revealed that axis 1, with a variance of 64.41%, explained more variation in terms of physico-chemical variables than axis 2. Temperature and pH were positively correlated with Station 2, while turbidity and phosphate were strongly positively correlated with Station 3. A total of 49 macroinvertebrate taxa and 5,814 individuals were recorded during the study period. Station 1 (3.038) had the highest macroinvertebrate individuals, followed by Station 2 (1.794). Bulinus globusus with 759 individuals was the most predominant taxon in the area. The canonical correspondence analysis (CCA) showed that axis 1 explained 86.98% of the ordination variance while axis 2 explained 13.02%. The two axes showed no significant correlation between macroinvertebrate taxa and physico-chemical variables. The CCA triplot showed that Melanoides moerchi, Culex sp., and Oligoneux sp. are surrogates for biomonitoring the Wupa River. We recommend further studies to be conducted along the entire stretch of the river to confirm our present results.