The widespread application of TiO₂ NPs will lead to their increasing release into the aquatic environment and thus affects the ecosystem function of aquatic life. As a microbial community, responses of periphytic biofilm to toxicity of TiO₂ NPs are largely unknown, in particular with respect to dynamic shifts of community structure and microbial functions of periphytic biofilms. Therefore, this study investigated the relationship between microbial functions and community composition of periphytic biofilms after chronic exposure (21 days) to 50 μg L⁻¹ and 500 μg L⁻¹ TiO₂ NPs. The increase of DOC in surface water was inhibited during the first 11 days (49.55%) by 500 μg L⁻¹ TiO₂ NPs and then recovered. Distinct responses were observed between community structure and microbial functions of biofilms after exposure to TiO₂ NPs. Specifically, both 50 μg L⁻¹ and 500 μg L⁻¹ TiO₂ NPs promoted the growth of microalgae (78.85–134.86%) and altered the bacterial community composition at day 7, and these trends lasted at day 21. In terms of the microbial functions determined using Biolog™ ECO microplates, biofilms maintained their total carbon metabolic activities under the stress of 50 μg L⁻¹ TiO₂ NPs. However, the carbon metabolic activities were significantly inhibited (24.63%) by the exposure to 500 μg L⁻¹ TiO₂ NPs at day 7 and then recovered to the control level at day 21. Although inhibition still existed in the metabolic activity for carbohydrate (17.00%) after long-term exposure, periphytic biofilms exhibited resistance to TiO₂ NPs and continuous decrease in nanotoxicity was observed.

中文翻译：

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长期暴露于TiO2 NPs期间周围植物生物膜的群落结构和微生物功能的动态响应

TiO ₂ NPs的广泛应用将导致其向水生环境中的释放增加，从而影响水生生物的生态系统功能。作为一个微生物群落，尤其是关于群落结构的动态变化和周围生物膜的微生物功能方面，周围生物膜对TiO ₂ NPs毒性的反应是非常未知的。因此，本研究调查了慢性暴露于50μgL ^-1和500μgL ^-1 TiO ₂ NPs （21天）后，微生物功能与周围生物膜的群落组成之间的关系。500μgL ^-1 TiO在最初的11天中抑制了地表水中DOC的增加（49.55％）_2个NP，然后恢复。暴露于TiO ₂ NPs后，在生物膜的群落结构和微生物功能之间观察到不同的响应。具体而言，在第7天，50μgL ^-1和500μgL ^-1的TiO ₂ NPs都促进了微藻的生长（78.85–134.86％）并改变了细菌群落组成，这些趋势持续到第21天。使用Biolog™ECO微孔板确定的微生物功能，生物膜在50μgL ^-1 TiO ₂ NPs的压力下保持了其总碳代谢活性。但是，暴露于500μgL ^-1 TiO _2会显着抑制碳代谢活性（24.63％）NPs在第7天，然后在第21天恢复到对照水平。尽管长期暴露后碳水化合物的代谢活性（17.00％）仍然存在抑制作用，但周生生物膜对TiO ₂ NPs表现出抗性并且观察到纳米毒性的持续降低。 。