[Department of Ocean Science] MPhil Thesis Defense Seminar: The Dual Role of Halophila Seagrass Meadows in Microplastics Trapping and Fungal-mediated Degradation
 

Abstract: 

Seagrass meadows are recognised as sinks for microplastic (MP) pollution, yet knowledge gaps persist regarding species-specific trapping mechanisms and the potential for seagrass-associated fungi to contribute to MP biodegradation. This thesis investigates MP trapping by three congeneric seagrasses (Halophila beccarii, H. ovalis, and H. minor) across a hydrodynamic gradient in Hong Kong, together with the polyethylene-degrading capacity of a novel seagrass-associated fungus, Halophilomyces hongkongensis. Field surveys confirmed a net trapping effect, though enrichment was species-dependent, detected in H. beccarii and H. ovalis but not H. minor. Selective retention followed an opposite pattern, demonstrating that quantitative enrichment and selective retention are functionally distinct. Concurrently, laboratory incubations demonstrated that H. hongkongensis induced significant polyethylene mass loss through a co-metabolic mechanism. Collectively, these findings demonstrate that seagrass contributes to MP mitigation through two distinct pathways: physical, species-selective trapping and biological degradation by associated fungi, highlighting the importance of incorporating both plant and microbial biodiversity into ecological risk assessments for coastal ecosystems.