Assessment of the ecological status of an ancient reservoir using macroinvertebrate assemblage and water quality parameters

Abstract Background Atori Reservoir, located in the heart of southwestern Nigeria, is a tribute to the region's historical significance and natural splendor. Its establishment as a reservoir in 1935 marked a water resource management watershed in the region, transforming Atori into one of Nigeria’s oldest and most important waterbodies. Despite its ancient age and indisputable importance, the exact ecological state of Atori Reservoir has been shrouded in mystery for decades. This study was necessitated by a paucity of information on the ecological status of Atori Reservoir. Results The study identified 953 macroinvertebrates belonging to four classes, distributed across nine orders and nineteen families within Atori Reservoir. Among these, the class Insecta exhibited the highest diversity, while Melanoides tuberculata, a member of the Mollusca class, emerged as the dominant species. Despite the diverse macroinvertebrate community, the physicochemical parameters of the water raised concerns. Elevated values of total dissolved solids and conductivity indicated poor water quality, which was further reflected in the predominance of pollution-tolerant species and the absence of pollution-sensitive ones. Canonical correspondence analysis highlighted potential correlations between macroinvertebrates and water quality variables, yet statistical significance was lacking, as demonstrated by the Monte Carlo permutation test. Conclusion This study sheds light on the ecological state of Atori Reservoir, revealing a diverse macroinvertebrate community but highlighting concerns regarding water quality. The study also emphasizes the pressing need for improved management practices to safeguard the ecological health of Atori Reservoir, given the critical role it plays in the region's ecosystem and local communities.