Tracing microplastics in environmental sources and migratory shorebirds along the Central Asian Flyway

Microplastic pollution poses a significant threat to coastal ecosystems worldwide. Despite its widespread occurrence, knowledge on the prevalence and fate of microplastics across food webs is limited. To bridge this gap, we conducted an extensive study on microplastic contamination in mudflats, mangroves, and sand beaches being key habitats for wintering shorebirds on the west coast of India. Using a comprehensive multi-matrix approach covering water, sediment, biofilm, plankton, benthic macroinvertebrates, and migratory shorebird droppings, we analysed microplastic contamination across ten coastal sites from 2020 to 2022. Our findings show spatial and temporal variations in microplastics widespread in water and sediments, influenced by human activities. Notably, an increase in microplastics within prey and shorebird droppings coincide with a decline in prey abundance and shorebird populations. The prevalence of fibre-shaped microplastics indicates that common sources include discarded fishing gear and domestic sewage. The types of microplastics ingested by shorebirds varied depending on their feeding strategies, with biofilms serving as significant reservoirs of microplastics, facilitating their transfer to shorebirds. Epibenthic feeders, with a more limited foraging range, displayed the lowest levels of microplastics, while species foraging through multiple sediment layers exhibited higher concentrations. These findings underscore the urgent need for stricter conservation measures to tackle plastic pollution at its source. The study raises concerns about the potential harmful effects of microplastic contamination on the population of migratory shorebirds along the west coast of India. Continued research is crucial to understand the ecological impacts of microplastics on wintering shorebirds and to develop effective conservation strategies.