Spatial distribution and ecological risk evaluation of microplastics in surface water, sediment, and Oreochromis niloticus from the Eravur sector, Batticaloa Lagoon, Sri Lanka

Abstract

Batticaloa Lagoon is a major and prominent coastal ecosystem in Sri Lanka. However, increasing anthropogenic activities around the Eravur sector have raised the plastic accumulation thus lead to concern of microplastic contamination and ecological risk. Therefore, this study intends to examine the abundance, spatial distribution and compositional characterization of microplastics in three separate aquatic environmental components such as surface water, sediment, and Oreochromis niloticus at the Eravur lagoon. Total microplastic abundance in surface water and sediment was 512.25, 412.33 ± 19.90 items L⁻¹ and ±29.26 items Kg⁻¹dry weight respectively with significantly higher concentrations at those sites located at lagoon shore (267.6 ± 15.4 items L⁻¹; 329.9 ± 22.3 items Kg-1) than lagoon sample sites (ANOVA, p < 0.001). Sediments had a greater proportion of microplastics (∼55 %) than surface waters, made of fragments and films, mostly white and transparent particles, and the smaller size fractions occupy the largest contributions to total counts (<1-2 mm-1-2mm: 30–34 %) in sediments; While in surface waters (2–4 mm: 41 %). Microplastics were found in 26 of 30 individuals of the O. niloticus (232 particles; 7.73 ± 6.8 ind⁻¹), dominated by filaments (∼69 %), mostly <1 mm (∼62 %), and ingestion was positively correlated with fish weight and length (r = 0.799 and r = 0.793, respectively; p < 0.001). FTIR confirms seven major polymer types where PET was most abundant in sediment (26 %), PS in surface water (30 %) and PE and PP in fish samples (25 % each). The evidence of active microplastic transfer shows significant impacts on lagoon ecology.