Impact of 2018 Kerala flood on the abundance and distribution of microplastics in marine environment off Cochin, Southeastern Arabian Sea, India

Abstract

The unfortunate event of the 2018 Kerala flood provided a unique opportunity to study the impact of flood events on the microplastic (MP) distribution in the marine environments of Cochin, Southeastern Arabian Sea, India. Monthly sampling of surface waters, bottom sediments, and beach sediments off the Cochin coast was conducted during March 2018–February 2019 to assess the abundance, composition, and distribution of MPs. Further, variation in MP contamination was analysed during pre-flood (March 2018–August 2018) and post-flood (September 2018–February 2019) periods. Results indicated that the flood caused a significant increase in the abundance of MPs in surface waters and beach sediments, but not in bottom sediments. In comparison with the pre-flood period, the MP concentration increased 3-fold in surface water and 1.5-fold in beach sediments during the post-flood period. MP concentration during the post-flood period was considerably greater than that during peak monsoon months (July–August). An increase in the diversity of MPs was also observed in all three ecosystems post flood. Furthermore, the local oceanographic conditions determined the retention time of MPs in the marine environment. The research findings underscore the importance of extreme weather events, such as floods, in reliably investigating the MP entry, its distribution, and accumulation in various environmental compartments of the marine ecosystem.