Numbere, A.O. and Aigberua, A.O., 2023. Characterization of tidally accumulated plastic waste and the effect on mangrove ecosystems at Eagle Island, Niger Delta, Nigeria. Journal of Coastal Research, 39(2), 275–283. Charlotte (North Carolina), ISSN 0749-0208.

Plastic pollution has become a global problem with the proliferation of numerous plastic goods. This study hypothesized that accumulated plastic waste will have a negative effect on the mangrove ecosystem and associated organisms. The study was performed in a sand-filled and deforested mangrove forest at Eagle Island, Niger Delta. Ten soil samples (n = 10) were collected under and around accumulated plastic waste at five different georeferenced sites. Samples of fish, crab, plastic, and foil from each site were collected and sent to the laboratory for physicochemical analysis of total hydrocarbon content (THC) and heavy metals, i.e. zinc (Zn), lead (Pb), and cadmium (Cd), using the HACH DR 890 colorimeter (wavelength 420 nm) and microwave accelerated reaction system (MARS Xpress, North Carolina, U.S.A.), respectively. Furthermore, microbial analysis was completed for the soil samples. A germination experiment was conducted in the laboratory using seedlings of Rhizophora racemose and Rhizophora mangle grown in plastic and nonplastic waste soils. The results show that no significant difference occurs in THC and heavy metal concentration in surface soils, subsurface soils (F_1,30 = 1.83, P = 0.186), and soils collected around plastic waste (F_3,28 = 0.60, P = 0.619). In contrast, a significant difference occurs in seedling growth between the control and plastic soils (F_4,200 = 65.24, P < 0.001). Microbial population showed significant difference horizontally, i.e. some distance away from plastic waste (near, middle, and far; F_3,11 = 3.86, P = 0.04) but not vertically (surface vs. subsurface; F_1,11 = 4.60, P = 0.055). These results indicate that chemicals in plastic waste can migrate outwardly to contaminate neighboring organisms. Thus, plastic waste should be quickly removed from the forest to prevent its decomposition and deposition of chemicals that will move up the food chain, affecting humans who consume seafood.