First baseline assessment of microplastic presence in the coastal sediments of Halfmoon Bay, Arabian Gulf

Global plastic production continues to rise, leading to the widespread accumulation of microplastics (MPs) in coastal environments. However, data on MPs in the Arabian Gulf are limited, especially for recreational beaches. This study presents the first comprehensive evaluation of MP presence on six sandy beaches in Halfmoon Bay, eastern Saudi Arabia. Eighteen surface sediment samples were collected following international monitoring protocols and analyzed using ZnCl₂ density separation, stereomicroscopy, and LUMOS II micro-ATR-FTIR spectroscopy. MPs were found at all sites, with average abundances of 60.83 ± 50.37 MPs kg-1 and 270.35 ± 175.35 MPs m-2. Abundance levels varied significantly among sites (p < 0.05), with Sadaf Beach having the highest levels and Aziziya South the lowest. Fibers were the most common MP shapes (39-78%), followed by filaments and fragments, while colored particles (80%) were more prevalent than white MPs. Particle sizes ranged from 17 to 2572 μm, with urban-influenced sites containing larger MPs. Micro-ATR-FTIR analysis identified nine polymer types among the spectroscopically validated particles, with PET and PP making up over 70% of the confirmed polymers. Despite lower content levels compared to other global hotspots, the presence of various polymers, including industrial materials, suggests multiple pollution sources. This baseline assessment highlights the importance of targeted management measures, including improved waste infrastructure, source-specific monitoring, and ongoing beach-cleaning efforts to reduce MP accumulation along Saudi Arabia's rapidly developing coastlines.