Microplastics pollution in aquatic ecosystems of Bangladesh — A critical review on research trends and future perspectives

The rapid proliferation of microplastics (MPs) has made them ubiquitous in the environment, especially in aquatic ecosystems. This review summarizes and compares the quantitative and qualitative occurrence of microplastics across all aquatic compartments including water, sediment, and biota and highlights current research trends, gaps, and future needs in Bangladesh. Recent field investigations in water, sediment, and aquatic organisms have confirmed widespread microplastics contamination across both marine and freshwater ecosystems. The country's marine water system has been found to contain microplastics in open water, nearshore sediments, saltpans, and alarmingly, within marine biota. Similarly, freshwater systems including aquaculture ponds, lakes, rivers, and estuarine environments have shown evidence of microplastics in their waters, sediments, and resident species. Microplastic abundance and characteristics showed significant spatiotemporal variation in both marine and freshwater systems. Meta-analysis of the existing literature showed that water and sediment contained, on average, 4.92 ± 0.95 (mean ± SEM) particles/L and 118.40 ± 16.12 (mean ± SEM) particles/kg, respectively. Microplastics numbers were greatest in freshwater fish (23.37 ± 4.25/fish; mean ± SD) and lowest in invertebrates (0.09 ± 0.02/individual; mean ± SD) followed by brackish water fishes (7.16 ± 1.18). Among the various polymer types identified, polyethylene (PE), polypropylene (PP), and polystyrene (PS) were consistently the most abundant, while fibers and fragment-shaped microplastics predominated across water, sediment, and biota. As a comprehensive synthesis of microplastics pollution in Bangladesh, this review may guide research, management, and policy decisions in the field.