Macroinvertebrates from two lotic environments: the Lésio River in a rural area and the Mfilou River in an urbanized environment, Republic of Congo

The study of benthic macroinvertebrates in the urban Mfilou River and the rural Lésio River aimed to evaluate the impact of anthropic actions and environmental variations on the quality of the biodiversity present. Benthic macroinvertebrates were sampled using Surber and Troubleau nets and the measurement of physicochemical parameters by electrometry and spectrophotometry. The waters of the Lésio River exhibited acidity, very low mineralization, an average temperature of 24.87±0.64°C, and normal organophosphate levels. Those of the Mfilou River appeared relatively neutral, with medium to medium-high mineralization, an average temperature of 26.88±0.78°C, and normal orthophosphate levels, while those of nitrogen compounds were high. A total of 169 taxa from 72 families were inventoried in the Lésio River and 129 taxa from 62 families in the Mfilou River. Diversity in the Lésio River is minimal at some sites and maximal at others, with significant pollution-sensitive groups observed. The Mfilou River, on the other hand, had maximal diversity, with waters extremely rich in pollution-resistant groups. In general, the benthic macroinvertebrates of the Lésio and Mfilou rivers present an opposite ecological state due to the disproportionate anthropogenic pressure they are subjected to. From the results obtained it can be stated that the waters of the Lésio River are suitable for human consumption.