Analysis of Structure and Composition of Macro-Invertebrate Assemblages in Natural Lukaya River Stream

Biological assessment of aquatic ecosystems is widely employed as an alternative or complement to chemical and toxicity testing due to numerous advantages of using biota to determine ecosystem condition. These advantages, especially to developing countries, include the relatively low cost and technical requirements. This study was carried out to establish relationship between water quality and macrozoobenthos assemblages along the Lukaya stream and to analyze fauna structure assemblages. Seven sites were selected along a 50-km stretch of the stream, which drained land under agricultural, residential and industrial uses. Water physico-chemical data was explored using multivariate analysis of Canonical Component Analysis to detect environmental trends. Water physico-chemical characteristics (temperature, pH, turbidity, conductivity, calcium, magnesium, nitrate, nitrite, sulphate and phosphate) and biodiversity indices (species richness, diversity, redundancy, evenness, abundance) did not show significant difference (P = 1) between sites along the stream but some correlation between variables and biodiversity indices were detected by spearman’s correlation analysis. Sixty-two taxonomic groups identified are dominated by odonata, diptera, shelfish and molluscs but three taxa: Lymnaeidae, Chironomyidae and Atyidae presented the highest abundance in all assemblages. The model of DIMO made it possible to split the various sites in two groups in function of H’, Hmax and J’. Moreover, rank-frequency diagrams of Frontier characterized stage 1 and middle between stages 1 and 2 structured curves.