Vertical distribution of microplastics in coastal sediments of Xuwen Coral Reef National Nature Reserve, China

Plastic pollution and microplastics in sediments are a growing concern for marine ecosystems worldwide. We examined the vertical distribution and properties of microplastics in beach sediments of Xuwen Coral Reef National Nature Reserve, in Leizhou Peninsula, Zhanjiang, China. Sediment samples were taken in seven locations at 5-cm intervals from the surface to a depth of 30 cm. The vertical distribution of microplastic particles ranged from 0 to 1 340 particles per kg on average of 119.05 particles per kg. The most prevalent material was fibers (76%), followed by film (12%), fragments (11.2%), and foam (0.8%). The microplastics in size of 1–2 mm constituted the largest percentage (40%) of the total, followed by those in size of <1 mm (26.4%), 2–3 mm (21.2%), 3–4 mm (9.6%), and 4–5 mm (2.81%). Site S1 observed maximum sizes between 1 and 2 mm, S2 reported higher availability of microplastics with sizes ranging from 0.3 to 1 mm. Six different types of polymers were identified in the investigation, and mostly were polyethylene (PE) and polypropylene (PP). In general, the observation of microplastics in deeper sediments indicates that they have the ability to last for prolonged periods in the marine environment, which may present long-term hazards to benthic creatures. In conclusion, the discovery of microplastics in deep layers of coastal sediments highlights the necessity of minimizing plastic waste and enhancing management strategies to safeguard marine environments.