Benthic macroinvertebrates diversity as bioindicators of water quality of Nasarawa Reservoir Katsina State Nigeria

Abstract

This study was carried out to assess the water quality of Nasarawa using benthic macroinvertebrates as bioindicators. Biological monitoring working party (BMWP) scoring system was the index used to assess the ecosystem health of Nasarawa reservoir. A total of 4460 macrobenthic invertebrate comprising three phyla, three classes, six families and seventeen species were recorded. The overall macrobenthic population at the different stations revealed that the study area was dominated by Mollusca (41.18%), Oligochaetae (23.53%), Coleoptera and Diptera (11.77%), Mollusca (29.06%), Ephemerophtera and Odonata (5.89%). (BMWP) score of 65.7 was obtained for Nasarawa reservoir which classifies the reservoir as moderately polluted. Higher BMWP score of 65.7 was recorded in the wet season compared to the dry season value of 58.7. More macrobenthic invertebrate population was recorded in the dry season than in the wet season in Nasarawa reservoir. Simpson (1-D), Shannon (H) and evenness were higher during the dry season than in the wet season but dominance was higher in the wet season. Species richness as revealed by the Margaleff and Menhinick index was higher during the wet season than in the dry season. The variations in taxa and number of individuals during the months of sampling was not significantly different (P>0.05). It was found that agricultural activities, washing and bathing could alter physico-chemical parameters of the stream and hence changing the abundance of macroinvertebrates as well as the quality of water. This study, therefore, recommends that the source of pollutants should be controlled and the stream regularly monitored by the relevant authorities.

Keywords: Benthic macroinvertebrates, Bioindicator, Water quality, Reservoir