Akinhanmi, Fadekemi and Covenant University, Theses (2024) MICROPLASTIC POLLUTION: OCCURRENCE, BIOLOGICAL IMPACTS AND GENE EXPRESSION PROFILING OF SELECTED FISH SPECIES IN THE LAGOS LAGOON, NIGERIA. ["eprint_fieldopt_thesis_type_phd" not defined] thesis, Covenant University.
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Abstract
Microplastics (MPs) are ubiquitous in the environment and have been a source of scientific concern. The detection of microplastics in edible aquatic species and the studies that highlight subsequent potential toxic effects under field conditions are few. Hence, this study determined the occurrence of microplastics and assessed their biological effect on selected commercial fish species in the Lagos Lagoon. Composite sampling technique was employed in retrieving surface water and benthic sediment samples from four locations; Badagry, Makoko, SagboKoji, and Epe, while selected fish species were procured directly from local fishermen and assessed for microplastic contamination. Thirty-two samples each of Chrysichthys nigrodigitatus, Oreochromis niloticus, Gymnarchus niloticus and Clarias gariepinus were analysed for microplastic contamination, oxidative stress, histopathology, and relative gene expression profile. Microplastics were observed and counted using a stereo microscope and plastic polymers were identified with Fourier-transform infrared spectroscopy. The gills, stomach, and liver were assessed for histopathological damage and oxidative stress using antioxidant enzyme biomarker; superoxide dismutase, glutathione, glutathione-S-transferase, and lipid peroxidation product, malondialdehyde. The relative gene expression profile of the fish liver was determined by the Real-time PCR analysis, with cytochrome 1a and heat shock protein 70 as the target genes, and ꞵ-actin as the reference gene. The seasonal variations in microplastic load and effects were determined in the sampling locations for inference. Statistical significance was established at p ≤ 0.05 between the abundance of microplastics across all the sampled locations. In the dry season, microplastic abundance was significantly high in Badagry at 71.4 ± 6.2 particles/L, and 3241.5±1069.5 particles/kg in the surface water and sediment respectively, whereas the fish species from Epe recorded the maximum microplastic presence at 34.7±9.4 particles/fish. In the rainy season, the microplastic load was predominant in the surface water and sediment from Badagry at 130.9 ± 7.0 particles/L and 5946.3 ± 543.7 particles/kg respectively, while high microplastic load (98.9 ± 35.8 particles/fish) was recorded in the fishes from Epe. Oreochromis niloticus accumulated the highest number of microplastics (38.2 particles/fish) in the dry season while Gymnarchus niloticus accumulated more (101.8 particles/fish) in the rainy season. Fibre was the predominant microplastic shape at 83% in surface water, 54% in sediment, and 61% in fish, with polyethylene, polychloroprene, and polyvinyl alcohol being the pre-eminent plastic polymer found. SOD activity and MDA levels were significantly higher in MP-laden fish tissues than in MP-free samples across both seasons (p ≤ 0.05). Stunted gill lamellae and degenerated necrotic hepatocytes were observed in the gill and liver of microplastic-contaminated fishes, respectively, while the stomach tissues showed no visible lesion. Cytochrome P450 gene was up-regulated as against the housekeeping ꞵ-actin gene in the contaminated fish liver. The microplastic load was significantly (p ≤ 0.05) higher in the rainy season than in the dry season. Biomarker responses in the fish species were also statistically higher in the rainy season than in the dry season. This study establishes an association between microplastic load in fish tissues and toxicological effects, calling for urgent measures to check microplastic contamination. However, further investigation is necessary to elucidate the risks and impact of chronic microplastic exposure on public health via the consumption of microplastic-contaminated fishes.
| Item Type: | Thesis (["eprint_fieldopt_thesis_type_phd" not defined]) |
|---|---|
| Uncontrolled Keywords: | Clarias gariepinus, gene expression, Lagos lagoon, microplastics, Oreochromis niloticus, oxidative stress |
| Subjects: | Q Science > QH Natural history Q Science > QH Natural history > QH301 Biology |
| Divisions: | Faculty of Medicine, Health and Life Sciences > School of Biological Sciences |
| Depositing User: | Patricia Nwokealisi |
| Date Deposited: | 05 Jul 2024 15:11 |
| Last Modified: | 05 Jul 2024 15:11 |
| URI: | http://eprints.covenantuniversity.edu.ng/id/eprint/18152 |
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