Several factors threaten the integrity of aquatic ecosystem resources in the Democratic Republic of Congo. The banks of the Pool Malebo (Congo River) are also vulnerable to the presence of plastic pollution in its waters. This study aims to inventory the different types of microplastics in three compartments (water, sediment and fish) of the Congo River in the part of the Pool Malebo between the fishing stations of Maluku and Kinsuka in Kinshasa. The search for microplastics was carried out by trapping with the Manta net. The identification and classification of plastic debris recorded in the three compartments of the Congo River were done on the basis of the density of microplastics. The results obtained showed that the physical and chemical parameters of the waters of the Congo River in the Pool Malebo generally contribute to the disintegration of macroplastics into microplastics. All the digestive tracts of the sampled fish have microplastics and the consequences on the food chain are obvious especially tourists and other populations consuming these fish. From the point of view of relative abundance of waste, PELD with 35 debris or 79.5% are the most numerous than PP with 9 debris or 20.4%. Given the danger that microplastics represent for aquatic animals and human health, further research based on the characterization of plastic waste by more advanced techniques will provide additional information on the composition of microplastics present in the Malebo Pool.

Fish Tilapia nilotica, Mormyrops anguilloides and Schilbe mystus, captured at port Socopla-Lomata on the Congo River in Mbandaka were analyzed by X-ray fluorescence spectrometer, brand Xepos III in accordance with the laboratory’s operating mode; to assess lead, cadmium and mercury contamination. The results showed concentrations higher than the edibility standards of the European Union and the concentrations observed in the water of the fishing site. The species Mormyrops anguilloides accumulates more cadmium while lead and mercury are more accumulated in Tilapia nilotica.

The effluents from the water treatment station of REGIDESO located in Kingabwa (Kinshasa city) are accused of reducing aquatic biodiversity of Matete and N'djili rivers and are responsible of some human diseases. The effects of these effluents on the physico-chemical and biological quality of water of Matete and N’djili rivers were evaluated. The benthic macro-invertebrates and Gambusia affinis were used as biodiversity richness indicator and model system for toxicity assays. The analyses of physicochemical parameters revealed a constant temperature in the stations studied (± 25 °C) and a high value of conductivity in the sites near the effluents discharge location. On the whole of the sites, the bacterial load was reduced to the neighboring sites of the effluents discharge. The pH is slightly acidic depending on the period and the sampling sites. Dissolved oxygen decreases as sampling seasons. 1405 specimens of benthic macro-invertebrates including 499 in the rainy season and 906 in dry season were harvested. The Shannon index value ranges from 0.4 to 2.9 during rainy season and 1.7 to 2.9 during dry season, reflecting the passage of polluted water to moderately pollute in rain season and moderately polluted to slightly pollute in the dry season. The toxicity bioassay revealed that these effluents are toxic (LC50= 0.109%). It is thus desirable to install a monitoring system near of the station of water purification of the REGIDESO N’djili in order to regularly control the dangerosity of the effluents poured in the surrounding watery ecosystems.