Athanase KUSONIKA NDAMBA
Works manager
Postgraduate Diploma (DEA) in Environmental Sciences

Thesis presented and defended publicly with a view to obtaining the title of Doctor of Science Group: Environment

Orientation : Food toxicology and aquatic ecotoxicology

Promoter

François Xavier MBUYI BADIBANGA MUSONGELA, Ph.D, Full Professor

Co-Promoters

Dieudonné Athanase MUSIBONO EYUL' ANKI, Ph.D

Ordinary Professor

Thierry TANGOU TABOU, Ph.D, Professor

Jury composition: President
Professor MALUMBA MUKA YA (PO/UNIKIN): Secretary
Professor NDELO-di-PHANZU (PO/UNIKlN): Promoter and Full Member
Professor MBUYI B.MUSONGELA (PO/UNIKIN): Full member
Professor MUSIBONO EYUL' ANKI (PO/UNIKIN): Full member
Professor NGELINKOTO MPIA (P/UPN): Alternate Member
Professor BIEY MAKAL Y (PO/UNIKIN): Alternate member
Professor KAYEMBE SUNGULA (PO/UNIKIN)

SUMMARY

This work presents the results for which the overall objective was to contribute to the study of the anthropized ecosystem of the Matete River in Kinshasa with a view to combating food insecurity and the disappearance of certain species from this aquatic ecosystem. The flood period constitutes a significant factor in the contribution of metallic elements. However, it offers a toxic habitat to the species that live there and could
directly influences their development, in particular, phosphorus of 0.011±0.001 and 0.325±0.07 mg/L during the dry season and 2.7±0.2 and 8.6±1.1 mg/L during the rainy season; potassium of <10.0±0.1 mg/L during the dry season and 17.7±0.6 and 207.2±0.4 mg/L during the rainy season; manganese of 0.5±0.4 mg/L and 9.1±0.1 mg/L during the dry season and <1.0±0.2 and 3999.0±905.6 mg/L during the
rainy season; iron of <1.0±0.8 mglL and 119500.0±3054.5 mg/L during the dry season and 21.5±0.7 and 1408.0±29.5 mg/L during the rainy season; cadmium of <0.00020±0.00002 mg/L and 2.4±0.3 mg/L during the dry season and <2.0 ±0.1 mg/L and 50.5 ±12.8 mg/L during the rainy season. In this regard, the flora of the Matete River accumulates metallic elements significantly and according to the diversity of the environments and the size of the species. In addition, the bioavailability of these trace metal elements and the physicochemical characteristics of the aquatic environment would be the key factors in the transfer of these metals from the abiotic environment to the biotic environment (cadmium: 2.8±0.3 and 25.6±0.4 mg/kg, lead: 0.5±0.4 and 86.7±5.5 mg/kg). One of the serious causes of their persistence is their bioamplification in the trophic chain. Therefore, the response of Pistia stratiotes and Lemna minor from nine sampling sites of the Matete River to high and/or low concentrations of metallic elements results in either an inhibition of photosynthetic processes (antagonism) and the extinction of some species. However, this ecosystem offers an ecological niche low in dissolved oxygen and a poor and toxic nutrient diet to the species living there. Under these conditions, the Matete River estuary, rich in chemical pollutants, constitutes a chemical barrier to ecological movements between its fauna and that of the N'djili River. Hence, the presence of only one species
of Oreochromis niliticus and its poor fish biological diversity. However, the Matete River is considered an enclosure and/or a natural happa whose fauna evolves in confinement. The Kinshasa population has difficult access to fish consumption, which is why the fish resources of this river are solicited. The lower the frequency of consumption (exposure), the less the effects are observable on the health of consumers.
Keywords : contribution, trace metal elements, anthropized ecosystem, trophic chain, consumers, Matete River, Kinshasa.