Distribution and abundance of microplastics in the water column of Vembanad Lake–A Ramsar site in Kerala, India

Abstract

The study focuses on the occurrence, abundance and characteristics of microplastics (MPs) in the subsurface and bottom waters of Vembanad Lake, a Ramsar site in the state of Kerala. Even though several studies elucidate the prevalence of microplastic pollution in the surface waters of aquatic ecosystems, a little is known about the vertical distribution of MPs in the water column. Vembanad Lake water is greatly affected by microplastic pollution compared to other Indian lakes as it receive discharges from six rivers; a number of sewage canals and run-off. Ubiquitous distribution of MPs was found in the lake with a mean abundance of 26.79 ± 3.74 items L−1 and 52.70 ± 5.43 items L−1 in subsurface and bottom waters respectively. Fibers, constitute more than half of the total MPs in both subsurface and bottom waters. The dominance of polyamide and polypropylene with most of the MPs being fibers indicate that they originate probably from fishing activities and laundry wastewater. The particles with in the size range 100–500 μm were in excess in the water samples. Further fragmentation, increasing the number of MPs in the lake water was envisaged from the SEM images of MPs showing cracks and crevices. These MPs along with adsorbed contaminants upon ingestion by the aquatic organisms become a threat to the food web of the lake. The local population which depends mainly on the fishes and mussels of the lake for their dietary needs would be greatly affected by the contamination of the lake with MPs. Further research on MPs contamination in edible biota would give more insights on the extent and risks of MPs pollution in the lake.