The Prevalence of Microplastics in Farmed Seaweed <i>Kappaphycus Alvarezii</i> in Panguil Bay, Philippines

Abstract Coastal inhabitants in the Philippines depend heavily on marine resources. However, seaweed farming, combined with increasing plastic pollution, raises environmental and health concerns due to microplastics entering the marine food chain. This study investigates the presence and characteristics of microplastics (MPs) in the seaweed Kappaphycus alvarezii and surrounding water samples from two farming sites in Panguil Bay, Philippines. FTIR analysis confirmed 1,298 microplastics across both sites, with 166 MPs in seaweed at Ozamiz and 109 at Kolambugan, averaging sizes from 0.24 to 4.99 mm. Analysis revealed that between the two sites and the three sampled group shows that there is a significant interaction effect in the number of MP particles. Microplastics have a higher concentration in water samples compared to seaweed at both sites, especially at Kolambugan. Characteristics of MPs indicated significant variations between washed and unwashed seaweed. Transparent MPs dominated Ozamiz, black MPs were more prevalent at Kolambugan. Fibers and filaments were the most common morphotypes. Rayon emerged as the most prevalent polymer, followed by polyester and azlon. Washing seaweed showed efficacy in MP removal, with Kolambugan showing a slight but significant. This suggests that washing can remove 33% of adsorbed MPs and alter their composition, potentially removing certain types more effectively. The findings emphasize the role of K. alvarezii as a biomonitor for MP pollution, providing valuable insights into the spatial variability and environmental impact of MPs in marine ecosystems.