Conserved Microbial Toxicity Responses for Acute and Chronic Silver Nanoparticle Treatments in Wetland Mesocosms

Abstract

Most studies of bacterial exposure to environmental contaminants focus on acute treatments; however, the impacts of single, high-dose exposures on microbial communities may not readily be extended to the more likely scenario of chronic, lowdose contaminant exposures. Here, in a year-long, wetland mesocosm experiment, we compared microbial community responses to pulse (single 450 mg dose of silver) and chronic (weekly 8.7 mg doses of silver for 1 year) silver nanoparticle (Ag 0 NP) treatments, as well as a chronic treatment of "aged" sulfidized silver nanoparticles (Ag 2 S NPs). While mesocosms exposed to Ag 2 S NPs never differed significantly from the controls, both Ag 0 NP treatments exhibited reduced microbial diversity and altered community composition; however, the effects differed in timing, duration, and magnitude. Microbial community-level impacts in the acute Ag 0 NP treatment were apparent only within the first weeks and then converged on the control mesocosm composition, while chronic exposure effects were observed several months after exposures began, likely due to interactive effects of nanoparticle toxicity and winter environmental conditions. Notably, there was a high level of overlap in the taxa which exhibited significant declines (>10×) in both treatments, suggesting a conserved toxicity response for both pulse and chronic exposures. Thus, this research suggests that complex, but short-term, acute toxicological studies may provide critical, costeffective insights into identifying microbial taxa sensitive to long-term chronic exposures to Ag NPs.

Long‐term accumulation, depth distribution, and speciation of silver nanoparticles in biosolids‐amended soils

“…The Ag 2 S nanoparticles in the biosolids are then transferred to soil when the biosolids are land applied (Chen et al, 2020;Wang et al, 2016;Yang et al, 2014). Silver-containing nanoparticles have been shown to negatively affect terrestrial organisms (Brami, Glover, Butt, & Lowe, 2017;Colman et al, 2013;Judy et al, 2015;Levard et al, 2013;Reidy, Haase, Luch, Dawson, & Lynch, 2013;Ward et al, 2019;Zhu et al, 2018). Examples of effects of Ag + and Ag(0) or Ag 2 S nanoparticles on terrestrial organisms include a decrease in tomato (Solanum lycopersicum L.) plant biomass, a decrease in mycorrhizal colonization of roots, and shifts in microbial community structure at concentrations from 100 to 1 mg kg −1 (Judy et al, 2015).…”

Environmental context determines the impact of titanium oxide and silver nanoparticles on the functioning of intertidal microalgal biofilms

“…85,97 Longer-term exposure to Ag-NPs could however potentially alter coastal biofilms and associated Environmental Science: Nano Paper processes through modification of the microbial community. 44…”

“…For instance, degradation processes are preponderant in winter, 52 and may be enhanced in the presence of ROS produced when NPs are present; this could explain the increased toxicity seen on this season. It is also interesting to note that chronic exposure to silver NPs in a wetland mesocosm also showed a higher sensitivity of prokaryotes in winter, 44 while winter communities of freshwater diatoms were more resistant to herbicides. 108 Our results highlight the necessity to repeat experiments under different environmental contexts encompassing different seasons and physiological states of the biological community under investigation, if we are to understand NP toxicity on the environment.…”

“…[40][41][42] Shifts in species composition of bacterial communities have been recorded at Ag-NP concentrations of 200 μg l −1 . 36,39,43,44 The link between alteration of community composition by NPs and modification of associated processes is not straightforward; for instance, bacterial activity to degrade hydrocarbons can be maintained in presence of Ag-NPs, despite significant modification of the composition of the bacterial communities. 36 Toxicity of NPs to microorganisms has also been shown to be taxon specific, 37 and influenced by environmental parameters, such as presence of UV light for TiO 2 -NPs 2 and Ag-NPs, 45 and temperature for Ag-NPs.…”

Bioelectrochemical recovery of silver from wastewater with sustainable power generation and its reuse for biofouling mitigation

“…Also, European Union has listed the silver as a priority pollutant for the aquatic environment (Directive 2006/11/EC) due to increased demand of silver-based products in Europe, North America, and Asia (Deycard et al, 2017). Presence of silver ions and silver nanoparticles (AgNPs) can lower the efficiency of biological wastewater treatment plants (Ward et al, 2019). Recently, a four percent increase in the global industrial demand and a two percent fall in mining supply of silver has been reported (Deycard et al, 2017;Dutta, 2019).…”