Microplastics and associated degrading microorganisms in marine sediments of the Arabian Gulf, Saudi Arabia: Assessment and characterization

Abstract

Microplastics (MPs) have become a pervasive pollutant in marine ecosystems. Still, their interactions with microbial communities under extreme environmental conditions remain poorly understood, particularly in the Arabian Gulf, one of the world’s most saline and hydrocarbon-rich marine basins. This study aimed to quantify and characterize MPs and their associated microbial consortia in coastal sediments near Jubail, Saudi Arabia, to elucidate their ecological risks and biotechnological potential. Sediment samples were collected from three sites representing industrial, fishing, and urban influences, with a total of 21 samples. Microplastics were isolated using density separation and identified via Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). At the same time, microbial diversity was analyzed using 16S rRNA gene sequencing and functional inference, and enzymatic and degradation pathways were predicted via PICRUSt2. Microplastics were detected in all sediment samples, with an average abundance of 1.86 ± 0.24 particles per gram (≈1860 particles kg⁻ 1 ), dominated by fibers (48%) and fragments (37%) composed mainly of polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). FTIR analysis revealed strong characteristic aliphatic C–H stretching bands (2917–2854 cm⁻ 1 ) indicating polymer identification. Microbial profiling showed polymer-specific community differentiation (PERMANOVA, R 2 = 0.41, p < 0.01), with significantly higher Shannon diversity (p < 0.05) in PE and PET than in PP. Key hydrocarbon clastic taxa, including Marinobacter, Alcanivorax, Pseudomonas, and Hydrogenovibrio, were enriched on polymer surfaces. Functional prediction identified xenobiotic-degrading pathways encoding Poly(ethylene terephthalate) hydrolase (PETase), Mono(2-hydroxyethyl) terephthalic acid hydrolase (MHETase), and the Alkane 1-monooxygenase (AlkB) monooxygenase, indicating intrinsic biodegradation potential under hypersaline conditions. These findings provide the first integrative evidence that microplastic–microbe interactions in Arabian Gulf sediments are both ecologically consequential and biotechnologically promising. The results highlight the Gulf as a natural reservoir of extremophilic, polymer-degrading bacteria, with implications for developing bioaugmentation and enzymatic recycling strategies tailored to arid, saline coastal systems. This study advances understanding of the plastisphere in extreme marine environments, addressing a critical knowledge gap in the global microplastic–microbe framework and offering novel perspectives for regional management and applied bioremediation.