Environmental Factors Shaping Microbial Biodegradation of Marine Microplastics

Marine microplastics have become a major challenge to the global marine environment because of their persistence and widespread distribution. Polyethylene (PE) and polyethylene terephthalate (PET), as the two most widely used and frequently detected polymers, exhibit markedly different biodegradation potentials due to their distinct chemical properties. This review systematically summarizes the microbial degradation mechanisms of PE and PET, including surface biofilm formation, key enzymatic reactions, aerobic and anaerobic metabolic pathways, and the synergistic effects of abiotic weathering with biological processes. Building on this, the review further analyzes how marine environmental factorstemperature, pressure, light, oxygen, salinity, and nutrient supplyaffect microbial degradation efficiency, with a particular focus on the contrasts between shallow and deep-sea systems. The findings indicate that temperature and oxygen availability are the primary limiting factors for plastic degradation in deep-sea environments, while high pressure, nutrient scarcity, and lack of light further constrain microbial metabolic activity. By integrating current research, this review highlights the central role of environmental drivers in shaping microplastic degradation, providing a theoretical foundation to better understand and enhance microbial degradation in marine ecosystems.