Abstract
Silver nanoparticles (AgNPs) are an emerging class of contaminants with the potential to impact ecosystem structure and function. AgNPs are antimicrobial, suggesting that microbe-driven ecosystem functions may be particularly vulnerable to AgNP exposure. Predicting the environmental impacts of AgNPs requires in situ investigation of environmentally relevant dosing regimens over time scales that allow for ecosystem-level responses. We used 3000 L enclosures installed in a boreal lake to expose plankton communities to chronic and pulse AgNP dosing regimens with concentrations mimicking those recorded in natural waters. We compared temporal patterns of plankton responses, Ag accumulation, and ecosystem metabolism (i.e., daily ecosystem respiration, gross primary production, and net ecosystem production) for 6 weeks of chronic dosing and 3 weeks following a pulsed dose. Ag accumulated in microplankton and zooplankton, but carbon-specific Ag was nonlinear over time and generally did not predict plankton response. Ecosystem metabolism did not respond to either AgNP exposure type. This lack of response corresponded with weak microplankton responses in the chronic treatments but did not reflect the stronger microplankton response in the pulse treatment. Our results suggest that lake ecosystem metabolism is somewhat resistant to environmentally relevant concentrations of AgNPs and that organismal responses do not necessarily predict ecosystem-level responses.
Highlights
Silver nanoparticles (AgNPs) are used in many industries because of their antimicrobial properties (Vance et al 2015)
We show that temporal patterns of lake plankton responses, including abundance and production, are complex and nonlinear following two realistic AgNP exposure scenarios and do not necessarily reflect Ag accumulation in the food web
We show that ecosystem metabolism was not affected by chronic or pulse AgNP exposure at environmentally relevant concentrations in “limnocorral” mesocosms in an oligotrophic boreal lake
Summary
Silver nanoparticles (AgNPs) are used in many industries because of their antimicrobial properties (Vance et al 2015). AgNP exposure can affect microbe abundance (Colman et al 2014), production (Das et al 2012a), photosynthetic activity (Gil-Allue et al 2015), exoenzyme activity (Colman et al 2012; Das et al 2012a), and stoichiometry (Das et al 2014). These studies were typically of short duration (but see Lowry et al 2012; Colman et al 2013, 2014). AgNPs have been shown to alter microbial processes that contribute to elemental fluxes at the ecosystem scale, including activity of enzymes associated with carbon, nitrogen, and sulfur cycling; microbial respiration; and organic matter decomposition (Tlili et al 2017; Vasileiadis et al 2018)
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