Microplastic Contamination on Cottonii Seaweed (Kappaphycopsis cottonii) Cultivated in Bomo Beach, Banyuwangi, East Java, Indonesia

The cultivation of Kappaphycopsis cottonii seaweed needs to comply with the health, waste, and sustainability in the Blue Economy standards. However, early observation showed that K. cottonii in Bomo Beach, Banyuwangi, East Java was potentially contaminated by microplastics. This research was performed to evaluate the density, polymer type, and contamination mechanism of microplastics in K. cottonii and the correlation between the planting age of K. cottonii and the total concentrations of microplastics in the seaweed. In this research, seaweed and seawater in the cultivated area were sampled using a simple random sampling technique every week for 5 weeks. Seaweed suspected of being contaminated with microplastics was digested using wet peroxide oxidation, followed by identification of polymer types through Fourier-Transform Infrared Spectroscopy (FTIR). The results indicated that the predominant suspected microplastics (MPs) contaminating K. cottonii were fibers, measuring less than 1.5 mm in size, and primarily composed of transparent polypropylene. MPs contaminate K. cottonii by wrapping around the thallus and being trapped by Melanothamnus savatieri (Hariot) Díaz-Tapia & Maggs epiphytes. The planting age of K. cottonii has a strong positive correlation with the number of suspected MPs contaminating K. cottonii. The growth of M. savatieri over a period of 3-4 planting weeks increases the suspected MPs on the thallus of K. cottonii. The results of this research can serve as a preventive measure and basis for developing strategic policies to reduce microplastic contamination. © 2025, Thai Society of Higher Eduation Institutes on Environment. All rights reserved.