Evidence of microplastics in Sargassum sp. in South coast of Sri Lanka

Abstract

The deposition of microplastic (MP) particles on marine macrophytes, such as macroalgae, is a possible entry point for MP into marine food webs. The present study was conducted to identify the MP associated with the most common seaweed species; Sargassum sp. grown on different tidal zones, i.e.: low-tidal zone (LTZ), mid-tidal zone (MTZ), and high-tidal zone (HTZ) on rocky shores in the Southern coast of Sri Lanka. The Sargassum samples (18/site) and water samples (3/site) were collected from all three tidal zones in Batheegama reef and Koggala reef. Sargassum blades were treated with 30% H2O2 solution, filtered and examined microscopically to identify MPs. The occurrence of MP was 100% for all seaweed and water samples. MP abundance in Sargassum in Koggala reef (2.72+1.45 particles/cm2) was significantly higher than that of Batheegama reef (1.94+0.60 particles/cm2). However, the MP abundance of water samples was not significantly different between Koggala (144.67 ± 48.95 particles/L) and Batheegama (147.60 ± 99.01 particles/L). In Koggala, MP abundance in Sargassum of MTZ was significantly lower than that at HTZ and LTZ. In Batheegama, the highest MP abundance in Sargassum was seen at the MTZ while that at the LTZ was the lowest. Significant variations were seen in the abundance of various MP types that were examined from the three tidal zones in Koggala and Batheegama. However, MP fibers were the most predominant type in water samples. In both Sargassum samples and water samples, black was the most abundant colour of MP, and small (<0.25cm) fibers were the most prominent type. Additional investigation is required to pinpoint the precise source, type of polymer, and the true impact of the microplastics on the ecosystem of the rocky shore