Development of macroinvertebrate multimetric index for ecological evaluation of a river in North Central Nigeria.

A macroinvertebrate-based multimetric index was developed for River Chanchaga, North Central Nigeria. Macroinvertebrates and physicochemical variables were sampled seasonally between March 2017 and February 2018 from four stations: station 1 (least impacted control station) and three downstream stations 2, 3 and 4. A total of 29 macroinvertebrate metrics in four categories, richness, abundance, composition and diversity, were evaluated for their potential to discriminate between the stations, seasonal stability and redundancy. Of the 29 metrics, only 13 fulfilled all criteria and were then integrated into the final Chanchaga multimeric index (MMIchanchaga). Application of the newly developed multimetric index revealed that water quality at stations 2 and 3 was fair and that of station 4 was poor. Water quality deteriorated slightly during the rainy season compared with the dry season. In terms of the individual component metrics, EPT richness, EPT (%) and Shannon diversity were highly sensitive to water quality impairment. The Bray-Curtis similarity measure revealed that stations 2 and 3 were more similar compared with the similarity between other stations. Overall, the newly developed multimetric index proved useful and represents the first important step in such index development in Nigeria.