Community structure and functional diversity of the plastisphere in aquaculture waters: Does plastic color matter?

Microplastics (MPs) serve as a niche for colonization of biofilm-forming microorganisms, termed as plastisphere. Distinct microbial assemblages between MPs and surrounding waters have been well reported, but little is known about driving factors affecting biofilm development on plastic surfaces. Here, to investigate the influence of plastic colors on microbial assemblages, we performed a biofilm incubation experiment, in an aquaculture pond, using MPs in colors (blue, yellow and transparent) that commonly found in the aquatic environments for 30 days. We examined the community structure and function of plastisphere by using 16S rRNA sequencing. The results showed that plastisphere communities exhibited a higher diversity and evenness compared with the water community. MPs especially the blue MPs had more unique species, which might indicate a plastic color/additive-driven selection of microorganisms on MPs. A significant distinctness in bacterial community composition between MPs and the water was found, mainly caused by large amounts of Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium but trace amounts of Microcystis_PCC-7914 on MPs. Due primarily to rich in Aquabacterium but lack of norank_f__norank_o__1-20 on blue MPs than on transparent and yellow MPs, a clear separation between plastisphere communities of three colors of MPs was also observed. Moreover, compared with the water column, the metabolic pathways, e.g., transport and metabolism of amino acid, carbohydrate and inorganic ion, on plastisphere especially those of blue MPs were generally enriched. Biofilms colonizing on blue MPs appeared to have a higher functional diversity than those on transparent or yellow MPs. These results might suggest that plastic colors have impacts on the community structure and functional diversity of plastisphere.