Environmental transformation and ecological interactions of spill-derived plastic resin nurdles following the MSC ELSA-3 spill, India.

Nurdle spills are recognised as sources of primary microplastic pollution, yet their long-term environmental transformation and ecological implications remain poorly understood. This study aimed to characterise the spatial and temporal persistence, environmental weathering, contaminant accumulation, microbial colonisation, and biological interactions of spill-derived nurdles following the MSC ELSA-3 incident. Contamination was monitored for one year across 93 coastal sites along India's southwest and southeast coasts using shoreline surveys, sediment coring, polymer and surface characterisation, contaminant analysis, microbial assessment, and fish examination. Shoreline abundance reached 31,230 items m-2 after the spill and declined by >80% within three months at impact sites, while new hotspots emerged by October 2025, reaching 10,875 items m-2 on the Gulf of Mannar mainland and 2960 items m-2 on islands. By May 2026, nurdles persisted and were found buried to 20 cm in beach sediments. Environmental exposure was associated with weathering as indicated by increases in Yellowing Index (5-64), Carbonyl Index (0.30-1.12), oxygen-containing functional groups, and surface deterioration observed by FTIR and SEM. Weathered nurdles accumulated heavy metals, PAHs (0.001-0.239 mg kg-1), resolved C8-C40 n-alkanes (TPH; up to 0.004 mg kg-1), and PCB-28 (0.012 mg kg-1), while heterotrophic bacterial abundance increased from 1 to >5 log₁₀ CFU g-1. Nurdles were detected in 26 of 2413 fishes (1.08%). Pristine nurdles caused minimal physiological disturbance, whereas weathered contaminant-enriched nurdles were associated with elevated oxidative stress and histopathological alterations. These findings provide evidence of environmental transformation and ecological relevance of spill-derived nurdles, highlighting the need for long-term monitoring and spill management.