Searching for indicator macroinvertebrate traits in an Afrotropical riverine system: implication for ecosystem...

In the past three decades, macroinvertebrate traits have been explored and employed in the biomonitoring of riverine systems globally, but much attention has not been given to the trait-based approach (TBA) in Nigeria. Therefore, in this study, the distribution patterns of macroinvertebrate traits in selected stations exposed to varying degrees of perturbation in River Hadejia, north-western Nigeria, were explored to assess the ecological health of the river. Three stations were selected, representing an increasing gradient of pollution: station 1 > station 2 and station 3, and were used to search for potential indicator traits. Four traits, including body size, respiratory, mobility, and body shape, were selected and classified into 12 trait attributes. The RLQ analysis revealed macroinvertebrates possessing medium and large body sizes, climbing and crawling, tegumental, gills, and aerial: lungs respiratory traits, and streamlined body shape were associated with station 1. Conversely, macroinvertebrates possessing very small and small body sizes, aerial: spiracle and aerial/vegetation, sprawling, swimming, and skating, flattened, spherical, cylindrical, and rhomboidal were mainly associated with stations 2 and 3. In searching for potential indicator macroinvertebrate traits aside from the RLQ analysis conducted, a fourth-corner analysis was further performed, which showed traits including medium and large body sizes, tegumental, and aerial: lung respiratory traits to be sensitive to pollution. Equally, aerial/vegetation, flattened body shape, and very small body size were found to be tolerant of pollution. A more robust trait-based biomonitoring study using more trait classes such as feeding mechanism, food preferences, voltinism, and attachment mechanism is recommended for future study in this region. The study would be helpful in biomonitoring of ecosystem health and enhance the sustainability prowess of the TBA in the studied region.