Microplastics affected bivalve microbial communities

Microplastics poses serious risk for organisms in aquatic environments. In particular bivalves are more vulnerable to microplastics due their filtration feeding strategy and sedentary life. While the effects of microplastic bioaccumulation in bivalves has been well documented, the effect of microplastics accumulation on bivalve's gut microbiome remains poorly understood. To fill this knowledge gap, , a feeding experiment with PET microplastic particles was conducted to investigate the effect of microplastic on the prokaryotic community in the gut of three bivalve species: Anadara cornea, Geloina expansa, and Meretrix meretrix taken from two contrasting locations (pristine, brackish water in Setiu Wetlands and polluted water in Kertih River) to investigate the legacy effect of pollutio in shaping community response towards microplastic exposure. The results showed that at 13 mg/L, microplastic increased diversity of gut microb es in G. expansa after 10 days treatment and caused negative effect on gut bacterial diversity in A. cornea by reducing the alpha diversity. In contrast, no significant changes of bacterial diversity was observed in M. meretrix. Higher species richness of gut bacteria was observed in in G. expansa from both locations as compared to M. meretrix and A. corneaGut bacteria in G.expansa collected from Kerteh river had higher species richness than that from Setiu Wetlands. We also observed significant effects of microplastic addition on relative abundance of bacteria l phyla Gut microbiome of G.expansa showed increase of the relative abundance of Arche a after microplastic exposure. There are distinct communities within the same bivalve species from Kertih and Setiu, and significant difference in Firmicutes, Bacteroidetes and Others community despite sharing similar OUT richness between the bivalve species from the same location. Reduction in gut microbiome diversity may explain the reduced survival of A. cornea in the wild. Results also suggested microplastic treatment supports dominancy of certain species, presumably with plastic-metabolizing ability, to provide species resiliency towards microplastic contamination and restore the bivalve health and availability in the environment.