Abundance, morphological traits, and polymer composition of ingested microplastics in Nile Tilapia (Oreochromis niloticus) from Batticaloa Lagoon

Abstract

The pollution of microplastics is a worldwide environmental issue that is continuously gaining evidence of creation in the environment and effects on the eco-health implications in aquatic systems. This paper evaluated the prevalence, properties, and polymer content of microplastics in Oreochromis niloticus (Tilapia) of the Eravur Lagoon (part of Batticaloa lagoon) in Sri Lanka. A total of sixty sexually maturing individuals were collected with the assistance of the local fishermen. Gastrointestinal tracts were removed, placed in 10 M NaOH (5:1 w/v) at 60◦C for 24 h, and then filtered through 0.25 mm mesh and observed under a stereomicroscope to categorise them on their shape, size and colour. FTIR analysis was used to confirm the polymer types. Statistical tests in SPSS entailed descriptive statistics, Pearson correlation, multiple regression, and one-way ANOVA with Tukey HSD. A total of 86 microplastic particles were retrieved, with an average of 1.43±1.42 particles per fish. Strong positive correlations were revealed between fish length (r = 0.736, p < 0.01), weight (r = 0.814, p < 0.01), and microplastic abundance; both variables were proven to be significant predictors with multiple regression analysis (R2= 0.682, p < 0.001). There were large proportions of filaments (66.28%) and few fragments (27.91%) and films (5.81%) (F (2,177) = 8.69, p < 0.001). The sizing category of <1 mm was significantly dominated by 56.98% of the particles compared to the 2 - 4 mm fraction (F = 14.62, p < 0.001). The black microplastics (58.14%) were found more significantly compared with transparent (23.26%), blue (12.79%) and green (5.81%) particles (F = 7.842, p < 0.001). The FTIR approach identified the presence of polyethylene, polypropylene, and nylon, which indicates their origin through fishing nets and packaging waste as well as textile effluents. These results reflect the vulnerability of Eravur Lagoon environment. The findings have the potential to inform guidelines on waste disposal, fishing equipment and education, and contribute a baseline dataset on which subsequent seasonal and trophic-level analysis can be built to inform national policy in plastic pollution reduction.