The Plastisphere in Saline Ecosystems: Quorum Sensing, Halotolerant Fungi and Microplastic Degradation Pathways

Plastic pollution has generated a novel anthropogenic habitat, the plastisphere, where microorganisms colonize and establish complex biofilms on the surfaces of synthetic polymers. Although considerable progress has been made in describing plastisphere microbial diversity, the ecological mechanisms linking community assembly, microbial communication, and polymer biodegradation remain poorly understood, particularly in saline ecosystems. Here, we review current knowledge on plastisphere formation in marine, estuarine, hypersaline, and other saline environments, emphasizing the ecological roles of quorum sensing (QS), halotolerant fungi, and microbial interactions in regulating biofilm development and microplastic degradation. We discuss how environmental factors characteristic of saline habitats, including osmotic stress, ultraviolet radiation, nutrient limitation, and high ionic strength, shape plastisphere succession and influence microbial physiology. Particular attention is given to halotolerant fungi, whose oxidative and hydrolytic enzymes—including laccases, peroxidases, cutinases, esterases, and lipases—complement bacterial metabolism during polymer transformation. We further examine recent evidence demonstrating that QS coordinates microbial attachment, extracellular polymeric substance production, biofilm maturation, extracellular enzyme secretion, and metabolic cooperation, thereby linking microbial communication with biodegradation efficiency. Based on current evidence, we propose an integrative ecological framework in which abiotic weathering, environmental filtering, quorum sensing, bacterial–fungal interactions, and extracellular enzymatic pathways constitute successive and interconnected processes governing plastisphere functioning in saline ecosystems. Finally, we identify major knowledge gaps and highlight future research priorities, including the integration of multi-omics approaches, synthetic microbial consortia, systems biology, and artificial intelligence for the discovery of novel plastic-degrading enzymes. By integrating microbial ecology, fungal biology, chemical communication, and environmental biotechnology, this review provides a systems-level perspective on the plastisphere and establishes a conceptual framework for understanding and enhancing microplastic biodegradation under saline conditions.