Seasonal and Spatial Variation in Microplastic Morphology in a Protected Tropical Freshwater Ecosystem: Evidence from Okomu National Park, Nigeria
DOI:
https://doi.org/10.33003/fjs-2026-1020-6091Keywords:
Microplastics, Freshwater Ecosystem, Morphological Composition, Seasonal VariationAbstract
Microplastic (MP) pollution in tropical freshwater ecosystems remains poorly characterized, particularly within protected landscapes. This study assessed the spatial and seasonal variation in MP morphology in surface waters of Okomu National Park, Nigeria. Water samples were collected from five sampling stations across two dry and two wet seasons, yielding 170 particles classified into six morphological categories: filament, fibre, foam, bead, fragment and plastic film. Filaments dominated the assemblage, accounting for 71.0% of particles during the dry season and 49.1% during the wet season. In contrast, fragments increased from 8.1% to 17.6%, while plastic films increased from 0% to 14.8% and occurred at all stations during the wet season. Seasonal morphology composition differed significantly (χ² = 20.45, df = 5, p = 0.001; Cramér’s V = 0.347), with filaments and plastic films representing the principal contributors to the observed shift. Morphological richness and Shannon diversity generally increased during the wet season, although paired station-level differences were not statistically significant. Spatially, morphological composition showed substantial overlap among stations, with no significant station-level association (χ² = 18.09, df = 20, p = 0.581; Cramér’s V = 0.163). These findings demonstrate seasonal restructuring of MP morphology despite limited spatial differentiation and provide a baseline for continued 29/09monitoring of plastic pollution in protected tropical freshwater ecosystems.
References
Adewuyi, A., & Li, Q. (2024). Emergence of microplastics in African environmental drinking water sources: A review on sources, analysis and treatment strategies. Journal of Hazardous Materials Advances, 16. https://doi.org/10.1016/j.hazadv.2024.100465
Anderson, M. J. (2001). A new method for non-parametric multivariate analysis of variance. Austral Ecology, 26(1), 32–46.
Andrady, A. L. (2011). Microplastics in the marine environment. Marine Pollution Bulletin, 62(8), 1596–1605. https://doi.org/10.1016/j.marpolbul.2011.05.030
Bray, J. R., & Curtis, J. T. (1957). An ordination of the upland forest communities of southern Wisconsin. Ecological Monographs, 27(4), 325–349.
Chen, D., Wang, P., Liu, S., Wang, R., Wu, Y., Zhu, A. X., & Deng, C. (2024). Global patterns of lake microplastic pollution: Insights from regional human development levels. Science of the Total Environment 954, 176620. https://doi.org/10.1016/j.scitotenv.2024.176620
Cheung, P.K., Hung, P.L., Fok, L., 2019. River microplastic contamination and dynamics upon a rainfall event in Hong Kong, China. Environmental Processes 6 (1), 253–264.
Cole, M., Lindeque, P., Halsband, C., & Galloway, T. S. (2011). Microplastics as contaminants in the marine environment: A review. Marine Pollution Bulletin, 62(12), 2588–2597. https://doi.org/10.1016/j.marpolbul.2011.09.025
Dahms, H. T. J., & Greenfield, R. (2025). Profiling microplastics in a forgotten river system in Southern Africa. Environmental Monitoring Assessment, 197(4), 351. https://doi.org/10.1007/s10661-025-13800-5
de Carvalho, A. R., Garcia, F., Riem-Galliano, L., Tudesque, L., Albignac, M., Ter Halle, A., & Cucherousset, J. (2021). Urbanization and hydrological conditions drive the spatial and temporal variability of microplastic pollution in the Garonne River. Science of the Total Environment, 769, 144479. https://doi.org/10.1016/j.scitotenv.2020.144479
Dinku, D. E., Ndur, S., Gyimah, E., Fosu, S., & Korley, P. (2025). Microplastics in African freshwater sediments: A systematic review of characteristics, abundance and analytical methods. Cleaner Water, 4. https://doi.org/10.1016/j.clwat.2025.100095
Guo, M., Noori, R., & Abolfathi, S. (2024). Microplastics in freshwater systems: Dynamic behaviour and transport processes. Resources, Conservation and Recycling, 205. https://doi.org/10.1016/j.resconrec.2024.107578
Gutierrez-Rial, D., Villar, I., Lagoa, A., Feijoo, P., Soto, B., Garrido, J., & Mato, S. (2025). Dynamics of microplastics in urban rivers under varying hydrological regimes. Journal of Hazardous Materials, 498, 139843. https://doi.org/10.1016/j.jhazmat.2025.139843
Hidalgo-Ruz, V., Gutow, L., Thompson, R. C., & Thiel, M. (2012). Microplastics in the marine environment: A review of the methods used for identification and quantification. Environmental Science & Technology, 46(6), 3060–3075. https://doi.org/10.1021/es2031505
Horton, A. A., Walton, A., Spurgeon, D. J., Lahive, E., & Svendsen, C. (2017). Microplastics in freshwater and terrestrial environments: Evaluating the current understanding to identify the knowledge gaps and future research priorities. Science of the Total Environment,, 586, 127–141. https://doi.org/10.1016/j.scitotenv.2017.01.190
Hu, T.-Y., & Kuan, W.-H. (2025). Seasonal rainfall and land-use impacts on microplastic characteristics in an endangered salmon stream. Scientific Reports, 16(1). https://doi.org/10.1038/s41598-025-33600-8
Li, J., Liu, H., & Chen, J. P. (2018). Microplastics in freshwater systems: A review on occurrence, environmental effects, and methods for microplastics detection. Water Research, 137, 362–374. https://doi.org/10.1016/j.watres.2017.12.056
Lusher, A. L., Hollman, P. C. H., & Mendoza-Hill, J. J. (2017). Microplastics in fisheries and aquaculture: Status of knowledge on their occurrence and implications for aquatic organisms and food safety. FAO Fisheries and Aquaculture Technical Paper No. 615. Rome, FAO.
McDonald, J. H. (2009). Handbook of Biological Statistics (2nd ed.). Sparky House Publishing.
Nel, H. A. & Froneman, P. W., 2015. A quantitative analysis of microplastic pollution along the south-eastern coastline of South Africa. Marine Pollution Bulletin 101, 274–279. https://doi.org/10.1016/J.MARPOLBUL.2015.09.043
Nyaga, M. P., Shabaka, S., Oh, S., Osman, D. M., Yuan, W., Zhang, W., & Yang, Y. (2024). Microplastics in aquatic ecosystems of Africa: A comprehensive review and meta-analysis. Environmental Research, 248, 118307. https://doi.org/10.1016/j.envres.2024.118307
Owowenu, E. K., Nnadozie, C. F., Akamagwuna, F., Noundou, X. S., Uku, J. E., & Odume, O. N. (2023). A critical review of environmental factors influencing the transport dynamics of microplastics in riverine systems: implications for ecological studies. Aquatic Ecology, 57(2), 557–570. https://doi.org/10.1007/s10452-023-10029-7
Range, D., Scherer, C., Stock, F., Ternes, T. A., & Hoffmann, T. O. (2023). Hydro-geomorphic perspectives on microplastic distribution in freshwater river systems: A critical review. Water Research, 245, 120567. https://doi.org/10.1016/j.watres.2023.120567
Schmidt, C., Krauth, T., & Wagner, S. (2017). Export of Plastic Debris by Rivers into the Sea. Environmental Science & Technology 51(21), 12246–12253. https://doi.org/10.1021/acs.est.7b02368
Shannon, C. E., & Weaver, W. (1949). The Mathematical Theory of Communication. University of Illinois Press.
Talbot, R., & Chang, H. (2022). Microplastics in freshwater: A global review of factors affecting spatial and temporal variations. Environmental Pollution, 292(Pt B), 118393. https://doi.org/10.1016/j.envpol.2021.118393
Tanaka, M., & Nihei, Y. (2026). How flooding rivers deliver plastic to the ocean: A case study of microplastic and mesoplastic load-discharge relationships. Water Research, 291, 125175. https://doi.org/10.1016/j.watres.2025.125175
Thanh, N. T., Toan, P. V., Minh, H. V. T., Lavane, K., Ngan, N. V. C., Ngan, L. T. K., Toan, V. T., Tuyen, N. V., & Kumar, P. (2026). Seasonal and Spatial Distribution of Microplastics in the Can Tho River (Mekong Delta, Vietnam): Occurrence and Characteristics. Microplastics, 5(3). https://doi.org/10.3390/microplastics5030136
Treilles, R., Gasperi, J., Tramoy, R., Dris, R., Gallard, A., Partibane, C., & Tassin, B. (2022). Microplastic and microfiber fluxes in the Seine River: Flood events versus dry periods. Sci Total Environ, 805, 150123. https://doi.org/10.1016/j.scitotenv.2021.150123
Wada, O. Z., Ijiwade, J. O., Ige, A. O., & Olawade, D. B. (2026). Recent occurrence of microplastics in freshwater and efficiency of available treatment technologies. Next Research, 3. https://doi.org/10.1016/j.nexres.2025.101074
Waldschläger K, & Schüttrumpf H. 2019. Effects of Particle Properties on the Settling and Rise Velocities of Microplastics in Freshwater under Laboratory Conditions. Environmental Science Technology 2019 Feb 19;53(4):1958-1966. doi: 10.1021/acs.est.8b06794. Epub 2019 Feb 11. PMID: 30688437
Yakubu, S., Miao, B., Hou, M., & Zhao, Y. (2024). A review of the ecotoxicological status of microplastic pollution in African freshwater systems. Science of the Total Environment, 946, 174092. https://doi.org/10.1016/j.scitotenv.2024.174092
Downloads
Published
Issue
Section
Categories
License
Copyright (c) 2026 Omobolanle Oluwatoyin Oyewole, Adetola Adetuga, Stephen Oluwabusayo Ajagbe, Ayokunle Tosin Ogundiya
This work is licensed under a Creative Commons Attribution 4.0 International License.
