Impact of hydrological and anthropogenic factors on the diversity of macroinvertebrates in a temporary stream of the western highlands of Cameroon

The Toela River, a temporary mountain stream, is difficult to access due to the steepness of its catchment area. However, increasing settlement and market gardening activities, sustained by irrigation from the river, have caused significant water stress, contributing to the temporary nature of the aquatic environment. This study aimed to assess the impact of such anthropogenic activities on the diversity of benthic macroinvertebrates in the Toela River. Environmental variables were measured using standard methods, and benthic macroinvertebrates were collected through a multi-habitat sampling approach. The results revealed strong spatio-temporal variability in physico-chemical parameters. Water temperature remained generally low, while dissolved oxygen reached up to 75% saturation during the rainy season. The acidic pH reflected the volcanic nature of the soils, and high orthophosphate concentrations indicated nutrient pollution of anthropogenic origin. A total of 743 specimens, representing 47 taxa, were identified, mainly arthropods (Diptera, Hemiptera), annelids, and platyhelminths, it is typical of tropical African freshwater systems. Species richness and diversity were significantly lower during the dry season, suggesting organic pollution. EPT taxa and Chironomidae exhibited clear seasonal and spatial variations linked to anthropogenic inputs and fluctuating hydrological conditions. Multivariate analyses highlighted pronounced ecological heterogeneity, distinguishing the downstream station (T3), with better ecological integrity, from the more impacted upstream stations (T1 and T2). Overall, the findings emphasise the combined influence of hydrological and anthropogenic factors in structuring benthic communities and the importance of sustainably managing water resources to preserve aquatic biodiversity in the Toela catchment.