Microplastics as carriers of pathogenic microbes in coastal ecosystems: A review Study

Microplastics (MPs) measuring less than 5 mm have been increasingly detected in the coastal regions of Iran, prompting significant concerns regarding environmental integrity and public health. Field investigations reveal their existence in coastal sediments, surface waters, and marine life; for example, reports indicate densities surpassing 3,000 particles per square meter along Hormozgan Province's shoreline. The majority of these particles consist of fibers and fragments from polyethylene, polypropylene, polystyrene, and polyethylene terephthalate, showing a considerable ability to absorb and transport chemical and microbial contaminants. A significant outcome of MPs in coastal ecosystems is the emergence of specialized microbial communities, known as the “plastisphere,” which settle on the surface of these plastic particles. These communities, comprising microorganisms from Gammaproteobacteria, Alphaproteobacteria, and Bacteroidetes, present notable differences from the surrounding environmental microbiota. Some of these microbes have the potential to harbor pathogens and antibiotic resistance genes (ARGs). While direct evidence from Iran’s coastal zones is sparse, the high concentration of MPs, along with global research findings, suggests that these particles may act as conduits for pollutants and pathogens, facilitating their movement through coastal food systems. This review emphasizes significant research deficiencies within Iran, especially regarding thorough microbial evaluations at surface and subsurface levels, identification of resistance genes, and modeling of microbial transfer. Future studies adopting an interdisciplinary framework that merges environmental engineering, microbiology, coastal ecology, and public health are vital for a deeper understanding of the environmental and health implications of microplastics. Ultimately, enhancing ongoing monitoring and establishing national guidelines for managing microbial contamination associated with microplastics are essential measures to safeguard coastal ecosystems and public health.