Keywords
Kinshasa
trace metals
urban river pollution
bacterial communities
ED-XRF
microbial ecotoxicology
How to Cite
Abstract
Introduction
Urban rivers in sub-Saharan Africa are increasingly affected by untreated domestic, industrial, and artisanal effluents, leading to polymetallic contamination that may alter microbial community structure and ecosystem functioning. However, the influence of chronic metal pollution on bacterial phenotypic composition remains poorly documented in tropical urban freshwater ecosystems.
Purpose
This study aimed to assess dissolved trace metal contamination along the Funa River (Kinshasa, Democratic Republic of the Congo) and investigate its relationship with the phenotypic distribution of cultivable bacterial communities.
Methods
A longitudinal survey was conducted at six sampling stations. Eighteen water samples were collected for physicochemical analyses, and nine composite samples were prepared for microbiological assessment. Ten trace metals were quantified using energy-dispersive X-ray fluorescence spectrometry (ED-XRF). Cultivable heterotrophic bacteria were enumerated on Mueller–Hinton and MacConkey media and characterized by Gram staining. Spatial differences were evaluated using the Kruskal–Wallis test, and associations between metal concentrations and bacterial phenotypes were examined using bootstrapped Spearman rank correlations (1,000 resamples).
Results
The Funa River exhibited severe polymetallic contamination, with several metals exceeding guideline values. Cadmium showed extremely high contamination factors (CF = 2,889--5,789), while lead reached 1,433 μg L-1 downstream. Dissolved iron varied significantly among stations (H = 6.14, p = .046). Total heterotrophic bacterial abundance ranged from (3.23 ± 1.53) x 106 to (3.73 ± 2.97) x 106 CFU mL-1. A marked shift in bacterial phenotype was observed, shifting from Gram-positive dominance upstream to exclusively Gram-negative populations downstream. Bootstrapped correlations revealed significant negative associations between most metal metrics and Gram-positive bacteria (ρ = -.50, p = .041), alongside corresponding positive associations with Gram-negative bacteria (ρ = +.50, p = .041).
Conclusion
Chronic polymetallic contamination acts as a strong ecological filter shaping bacterial community structure in the Funa River, favoring Gram-negative populations adapted to metal stress. These findings underscore the need for improved urban wastewater management and molecular investigations to resolve microbial adaptation pathways and public health risks.
References
Ali, B., Khan, A., Ali, S. S., Khan, H., Alam, M., Ali, A., Alrefaei, A. F., Almutairi, M. H., & Kim, K. I. (2023). Heavy metals and microbial diversity: A comparative analysis of Rivers Swat and Kabul. Water, 15(18), Article 3297. https://doi.org/10.3390/w15183297
Allan, J. D., & Castillo, M. M. (2007). Stream ecology: Structure and function of running waters (2nd ed.). Springer.
American Public Health Association. (2012). Standard methods for the examination of water and wastewater (22nd ed.). APHA Press.
Ayangbenro, A. S., & Babalola, O. O. (2017). A new strategy for heavy metal polluted environments: A review of microbial biosorbents. Chemosphere, 185, 136–146. https://doi.org/10.1016/j.chemosphere.2017.06.145
Azarbad, H., Niklińska, M., van Gestel, C. A. M., van Straalen, N. M., & Röling, W. F. M. (2013). Microbial community composition and functions are resilient to metal pollution along two forest soil gradients. FEMS Microbiology Ecology, 84(2), 364–378. https://doi.org/10.1111/1574-6941.12069
Canadian Council of Ministers of the Environment. (2022). Canadian water quality guidelines for the protection of aquatic life. CCME.
Chen, J., Wu, H., Liu, Y., Li, Z., & Sun, Z. (2022). Heavy metal contamination and its influence on bacterial community structure in river sediments of the Yangtze River. Science of the Total Environment, 838, Article 156428. https://doi.org/10.1016/j.scitotenv.2022.156428
Cohen, J. (1988). Statistical power analysis for the behavioral sciences (2nd ed.). Lawrence Erlbaum Associates.
Daly, K., & Fenelon, A. (2018). Application of energy dispersive X-ray fluorescence spectrometry to the determination of copper, manganese, zinc, and sulfur in grass (Lolium perenne) in grazed agricultural systems. Applied Spectroscopy, 72(11), 1661–1673. https://doi.org/10.1177/0003702818787165
Dean-Ross, D., & Mills, A. L. (1989). Bacterial community structure and function along a heavy metal gradient. Applied and Environmental Microbiology, 55(8), 2002–2009. https://doi.org/10.1128/aem.55.8.2002-2009.1989
Fajardo, C., Costa, G., Nande, M., Botías, P., García-Cantalejo, J., & Martín, M. (2023). Heavy metals influence the structure and function of soil microbial communities. Agriculture, 13(3), Article 653. https://doi.org/10.3390/agriculture13030653
Field, A. (2024). Discovering statistics using IBM SPSS Statistics (6th ed.). SAGE Publications.
Gadd, G. M. (2010). Metals, minerals and microbes: Geomicrobiology and bioremediation. Microbiology, 156(3), 609–643. https://doi.org/10.1099/mic.0.037143-0
Hakanson, L. (1980). An ecological risk index for aquatic pollution control: A sedimentological approach. Water Research, 14(8), 975–1001. https://doi.org/10.1016/0043-1354(80)90143-8
Hu, X., Zhao, L., Ding, Z., Gao, X., & Han, G. (2026). Tooth enamel as a biogeochemical archive of trace elements in an urban population: A multielement study from Beijing, China. Biological Trace Element Research, 204(2), 412–425. https://doi.org/10.1007/s12011-026-05036-2
International Organization for Standardization. (2024). Microbiology of the food chain—General requirements and guidance for microbiological examinations (ISO Standard No. 7218:2024).
Kapembo, M. L., Mukeba, F. B., Sivalingam, P., Mukoko, J. B., Bokolo, M. K., Mulaji, C. K., Mpiana, P. T., & Poté, J. (2021). Survey of water supply and assessment of groundwater quality in suburban zones of Kinshasa, Democratic Republic of the Congo. Waste Management, 120, 238–248. https://doi.org/10.1016/j.wasman.2020.11.040
Kayembe, J. M., Bokwokwo, M. I., Sivalingam, P., Ngelinkoto, P., Otamonga, J.-P., Mulaji, C. K., Mubedi, J. I., & Poté, J. (2020). Effect of untreated urban effluents on the accumulation of toxic metals in river sediments under tropical conditions: Funa River, Kinshasa, Democratic Republic of the Congo. Water and Environment Journal, 34(2), 180–188. https://doi.org/10.1111/wej.12451
Kyowire, K. P., Luamba, L. N. J., Kamb, T. J.-C., Sisa, M. E., Munganga, G. J., & Bunda, P. M. N. (2024). Évaluation de la qualité physico-chimique et bactériologique des eaux des puits et forages des quartiers Batumona, Biyela et Luebo dans la commune de Kimbanseke à Kinshasa (RDC). International Journal of Progressive Sciences and Technologies, 47(2), 257–270.
Lia, F., Zammit Mangion, M., & Farrugia, C. (2020). Application of elemental analysis via energy dispersive X-ray fluorescence (ED-XRF) for the authentication of Maltese extra virgin olive oil. Agriculture, 10(3), Article 71. https://doi.org/10.3390/agriculture10030071
Liu, C., Zhou, K., Qin, W., Tian, C., Qi, M., Yan, X., & Han, W. (2020). A review on heavy metals contamination in soil: Effects, sources, and remediation techniques. Science of the Total Environment, 715, Article 136974. https://doi.org/10.1016/j.scitotenv.2020.136974
Mabidi, D. M., Manyingu, H. M., Ngakiama, G. B., & Poté, J. (2024). Trace metal contamination and ecotoxicological risk assessment in Congo River sediments around Kinshasa. Environmental Monitoring and Assessment, 196(4), Article 312. https://doi.org/10.1007/s10661-024-12450-1
Madigan, M. T., Bender, K. S., Buckley, D. H., Sattley, W. M., & Stahl, D. A. (2018). Brock biology of microorganisms (15th ed.). Pearson.
Manza, H. M., Kiyombo, G. M., Kuna, S. N., Carvalho, F. P., Poté, J., Atibu, E. K., & Mata, H. K. (2026). Trace metal levels in sediments and muscle of edible fish species from the Kasai River, Democratic Republic of the Congo. Water, Air, & Soil Pollution, 237(13), Article 765. https://doi.org/10.1007/s11270-026-09437-w
Mukeba, F., Kapembo, M., Mpiana, P., Mulaji, C., & Poté, J. (2022). Approvisionnement et évaluation de la qualité des eaux souterraines de Selembao et Kimbanseke. Revue Congolaise des Sciences Humaines et Sociales, 1(2), 1–18. https://doi.org/10.59189/crsh102240
Muter, O., Gudrā, D., Daumova, G., Idrisheva, Z., Rakhymberdina, M., Tabors, G., Dirnena, B., Dobkeviča, L., Petrova, O., Apshikur, B., Luņģe, M., Fridmanis, D., Dennisov, I., Bekishev, Y., Kasparinskis, R., Mukulysova, Z., & Polezhayev, S. (2024). Impact of anthropogenic activities on microbial community structure in riverbed sediments of East Kazakhstan. Microorganisms, 12(2), Article 246. https://doi.org/10.3390/microorganisms12020246
Mwanamoki, P. M., Devarajan, N., Niane, B., Ngelinkoto, P., Thevenon, F., Nlandu, J. W., Mpiana, P. T., Prabakar, K., Mubedi, J. I., Kabele, C. G., Wildi, W., & Poté, J. (2015). Trace metal distributions in the sediments from river-reservoir systems: Case of the Congo River and Lake Ma Vallée, Kinshasa (Democratic Republic of Congo). Environmental Science and Pollution Research, 22(1), 586–597. https://doi.org/10.1007/s11356-014-3381-y
Nakagawa, S., Lagisz, M., Yang, Y., & Drobniak, S. M. (2024). Finding the right power balance: Better study design and collaboration can reduce dependence on statistical power. PLOS Biology, 22(1), Article e3002423. https://doi.org/10.1371/journal.pbio.3002423
Nsiala, O. G., Mukeba, B. F., Seke, V. M., Bamvingana, K. C., Kacha, M. M., Matumona, K. D., & Biey, M. E. (2025). Risk and recurrence of waterborne diseases linked to groundwater quality in the Hérady district of Selembao (Kinshasa, DRC). Orapuh Journal, 6(12), Article e1318. https://doi.org/10.4314/orapj.v6i12.118
Silhavy, T. J., Kahne, D., & Walker, S. (2010). The bacterial cell envelope. Cold Spring Harbor Perspectives in Biology, 2(5), Article a000414. https://doi.org/10.1101/cshperspect.a000414
Sun, X., Zhang, L., Liu, H., Wang, Z., & Giesy, J. P. (2021). Ecotoxicological risk assessment of metal cocktails based on maximum cumulative ratio during multi-generational exposures. Water Research, 200, Article 117274. https://doi.org/10.1016/j.watres.2021.117274
U.S. Environmental Protection Agency. (2007). Method 1694: Pharmaceuticals and personal care products in water, soil, sediment, and biosolids by HPLC/MS/MS (EPA Publication No. 821-R-08-002).
Ukoumunne, O. C., Davison, A. C., Gulliford, M. C., & Chinn, S. (2003). Non-parametric bootstrap confidence intervals for the intraclass correlation coefficient. Statistics in Medicine, 22(24), 3805–3821. https://doi.org/10.1002/sim.1643
Wang, M., Wang, Y., Wu, Y., Ma, Q., Huang, J., He, T., Huang, S., & Chen, C. (2024). Exploring the long-term impact of a cadmium pollution accident on microbial communities in river ecosystems. Biogeochemistry, 167(8), 1123–1137. https://doi.org/10.1007/s10533-024-01150-2
Willey, J. M., Sherwood, L. M., & Woolverton, C. J. (2017). Prescott's microbiology (10th ed.). McGraw-Hill Education.
World Health Organization. (2022). Guidelines for drinking-water quality: Fourth edition incorporating the first and second addenda. WHO Guidelines Approved by the Guidelines Review Committee.
Yang, D., Hou, Y., Wei, C., Ling, J., & Zheng, X. (2025). Aquatic microcosms in ecotoxicology: The community-level ecological risk assessment of pollutants. Toxics, 13(8), Article 694. https://doi.org/10.3390/toxics1308694
Yi, J., Wang, Y., Zhang, S., Liu, H., Lv, J., Zhu, L., & Zhou, Y. (2021). Study of heavy metals and microbial communities in estuarine sediments of the Yangtze River estuary. Frontiers in Marine Science, 8, Article 741912. https://doi.org/10.3389/fmars.2021.741912
Zeb, M., Khan, K., Younas, M., Farooqi, A., Cao, X., Kavil, Y. N., Alelyani, S. S., Alkasbi, M. M., & Al-Sehemi, A. G. (2024). A review of heavy metals pollution in riverine sediment from various Asian and European countries: Distribution, sources, and environmental risk. Marine Pollution Bulletin, 206, Article 116775. https://doi.org/10.1016/j.marpolbul.2024.116775
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