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
