Microplastic Contamination Alters Seagrass Nutritional Quality and Gut Microbiome Stability in Dugong (Dugong dugon): An Integrated One Health Assessment in Tropical Coastal Ecosystems

The dugong ( Dugong dugon ) is a vulnerable marine herbivore whose survival depends on the ecological integrity of tropical seagrass ecosystems. This study evaluated the relationships among microplastic contamination, seagrass nutritional quality, gut microbiome diversity, parasite prevalence, and physiological stress indicators across five coastal stations in North Lombok, Indonesia. Field sampling was conducted from March to October 2025. Microplastics were quantified using FTIR spectroscopy, seagrass nutrient composition was analyzed following AOAC standards, and 25 non-invasive fecal samples were subjected to 16S rRNA sequencing and ELISA-based cortisol analysis. Multivariate regression, principal component analysis (PCA), and structural equation modeling (SEM) were applied. Microplastic concentration was negatively associated with microbiome diversity (β = −0.71, p < 0.01) and positively associated with fecal cortisol (β = 0.64, p < 0.05). Seagrass protein content positively correlated with microbial diversity (r = 0.69) and inversely with parasite prevalence (r = − 0.58). SEM supported an indirect pathway linking pollution to physiological stress through microbiome-mediated mechanisms (CFI = 0.94, RMSEA = 0.06). These findings provide empirical evidence that coastal pollution disrupts digestive ecological stability in dugongs and underscore the importance of integrating pollution control with seagrass habitat conservation.