Preliminary studies on macroinvertebrate biomonitoring of freshwater systems in the Afrotropics: a case study of the Chanchaga River in the Lower Niger-Benue Ecoregion of Nigeria | Request PDF

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In the developing nations like Nigeria, the science of freshwater biomonitoring is still scanty unlike developed countries. In this study, we explored the significance of using macroinvertebrates for biomonitoring of the Chanchaga River in the Lower Niger-Benue Ecoregion of Nigeria in four stations sampled for 14 months which covered both wet and dry seasons. Physico-chemical variables were analysed following standard procedures while macroinvertebrates were collected using kick sampling technique. Proportionately high values of physico-chemical variables such as nutrients, BOD and conductivity portraying increasing pollution were observed in stations 3 and 4 unlike the less disturbed stations 1 and 2. A total of 12,210 macroinvertebrates comprising of 94 taxa belonging to 11 orders and 54 families were collected during the study period. In the entire study, we recorded a total of 57.53% of macroinvertebrates during the wet season months and 42.47% in the dry season months. The canonical correspondence analysis (CCA) result revealed no marked seasonal variation in the relationship between macroinvertebrates and physico-chemical variables. Pollution tolerant taxa such as Tipula sp., Culex sp., Chironomus sp., Unionidae and Dugesia polychroa were associated with stations 3 and 4 in both wet and dry seasons. Our result from the analysis of similarity (ANOSIM) revealed that station 4 had the highest similarities in terms of macroinvertebrates distribution, while the result of the similarity percentage (SIMPER) indicated 91.73% dissimilarity in macroinvertebrates taxa between stations 1 and 4. This confirmed one of our hypotheses which states that macroinvertebrates will respond differentially to pollution gradients across the stations sampled. We concluded that the present study will serve as vista to biomonitoring of freshwater systems in the Afrotropical region. However, the study did not unveil the functional ecology of the macroinvertebrate assemblage. We therefore recommend that a combination of structural and functional ecology of freshwater systems should be explored in future studies.