Abundance and characteristics of plankton and microplastics along the northern coastline of Central Java, Indonesia

This study aimed to characterize microplastics (MPs) and analyze the composition of plankton in the coastal waters of Central Java's North Coast. The examined characteristics of MPs comprise type, color, size, polymer type, and chemical properties. The plankton samples were classified according to species and size. The study results indicated that the overall abundance of MPs (83 particles/L) across all locations in these coastal waters was significantly higher than that of plankton (57 individuals/L). The concentration of MPs ranged from 10 to 42 particles/L, with Jepara demonstrating the highest level at 42 particles/L. The distribution of plankton among all locations exhibited little variation, ranging from 13 to 15 ind/L at each site. The predominant size of both MPs and plankton was ≤1 mm. MPs measuring ≤1 mm constituted 98 % of the total MPs, whereas plankton of the same size represented 94.7 % of the total plankton. Copepods exhibited the most diversity in size classes, demonstrating abundance in greater categories (>1–2 mm and >4–5 mm), whilst other taxa primarily demonstrated abundance in the ≤1 mm size class. The study identified a variety of MPs, such as fibers, fragments, films, and pellets. Fibers (38.8 %) were the most prevalent form, followed by fragments (31.2 %) in all location. The most prevalent color was black, with 44.8 % of the total, while transparent was second at 29.6 %. Seven polymer types, including polyethylene (PE), polypropylene (PP), low-density polyethylene (LDPE), polystyrene (PS), polyethylene terephthalate (PET), polyurethane (PU), and polyacrylonitrile (PAN), were analyzed utilizing FTIR imaging, with PET being abundantly detected at all sampling sites. This research presents baseline data regarding the concurrent distribution of microplastics and plankton in the coastal waters of northern Central Java. The study enhances the understanding of microplastic dynamics in coastal environments through the comparison of quantitative abundance, size-class analysis, and FTIR-based polymer identification.