Effective acid treatment and investigation of microplastics in two common hard corals from Pulau Redang Marine Park, Malaysia

The emergence of microplastics (MPs) pollution in the ocean is a significant threat to coral reefs. This study assessed MPs in two common hard corals ( Acropora and Porites ) from Pulau Redang, a marine protected island located offshore in the southern South China Sea, Malaysia. Acid digestion method was preliminarily tested on the entire coral fragments to determine a suitable concentration preserving MPs. A total of 200 coral fragments were collected from five sites and categorized by health status. Samples were digested using a validated concentration (5% hydrochloric acid) and analyzed for MPs content. Results found MPs in 64% of the corals, with the abundance linked to proximity of development recorded the highest mean at Long Beach (1.31 ± 2.59 items/g), followed by Pasir Akar (0.85 ± 1.26 items/g), Kerengga Besar (0.72 ± 0.97 items/g), Chagar Hutang (0.54 ± 0.74 items/g) and Mak Simpan (0.47 ± 0.57 items/g). Although MP abundance showed no significant difference between coral genera, unhealthy Acropora had three times more MPs overgrown in coral fragments entangled with plastic debris. Characterization of MPs revealed dominant colours of black and transparent. Fibre was the dominant shape, and particle sizes were primarily distributed in two ranges: < 300 µm and 1000–5000 µm. Among polymers identified using µ-FTIR, polyethylene terephthalate (PET) was the main synthetic plastic found in corals. The findings provide a crucial baseline on MP contamination in coral reefs within Malaysia marine park, and highlight the concern over plastic pollution risk in ecologically valuable marine ecosystems. • Microplastics pollution evidenced in corals from Pulau Redang Marine Park Malaysia • Debris entangled corals have more microplastics overgrowth in the colonies • Polyethylene terephthalate is the main microplastics polluted the corals • 5% HCl acid digests coral skeleton with minimum impacts on microplastics