TiO nanoparticles exert an adverse effect on aquatic microbial communities.

Titanium dioxide nanoparticle (n-TiO) is a widely used nanomaterial, which is inevitably released as a residue into aquatic ecosystems during material production and usage. However, the effects of n-TiO on aquatic microbial communities have not been completely elucidated. This study examined the toxic effects of n-TiO on eukaryotic and prokaryotic microbial communities in freshwater environments. We determined that n-TiO had a greater inhibitory effect on the growth of eukaryotic algae than cyanobacteria in monocultures. A similar phenomenon was observed in a microcosm experiment, revealing that n-TiO slightly reduced the content of chlorophyll-a but evidently increased the phycocyanin content. Moreover, the alpha diversity of the eukaryotic community was not affected, whereas its beta diversity increased with exposure to n-TiO. Although n-TiO altered the composition of freshwater microbial communities, it did not change the functions of the prokaryotic community, which might be attributed to the functional redundancy of microbiota. Co-occurrence network analysis indicated that n-TiO destabilized the freshwater community, especially the eukaryotic community, and potentially disturbed the aquatic ecosystem. Our study revealed that the ecological risk of n-TiO on aquatic microbial communities is complex; hence, rational utilization of n-TiO should be emphasized.