Microplastics in Freshwater Aquaculture: Evidence of Sediment-Fish Transfer and Associated Ecological Risks in Bangladesh.

Abstract

Microplastics (MPs) in aquaculture systems in Bangladesh threaten ecosystem health and food safety. This study examined MPs in surface sediments and farmed fish from 25 aquaculture ponds in Trishal Upazila, Mymensingh. Most sites were moderately to highly polluted, with a pollution load index (PLI) ranging from 1.0 to 4.5, while mean sediment MPs concentrations were 11.04 ± 3.75 particles kg-1. For fish, a total of 90 MPs were detected, with a mean abundance of 0.60 ± 1.16 MPs fish-1. Demersal fish (52%) demonstrated the greatest ingestion rates, followed by benthopelagic (35%) and pelagic species (13%). The major polymers detected were PE and PP, showing ubiquitous plastic origins in aquaculture and household activities. Frequency of occurrence (FO%) ranging from 16% to 40% revealed uneven fish species MPs ingestion rate. Fulton's condition factor (K: 0.35-2.27) varied among species, with lower values observed in Catla catla and Pangasius pangasius, which also showed relatively higher MPs ingestion. Higher bioconcentration (BCF) values in Cirrhinus cirrhosus, Cyprinus carpio and Pangasius pangasius indicating MPs magnification through the food chain. Overall, the widespread ingestion of MP by cultured fish highlights their potential ecological impacts within Bangladesh's aquaculture systems and underscores the urgent need for targeted monitoring and sustainable management strategies to mitigate MP contamination.