title: Chronic and pulse exposure effects of silver nanoparticles on natural lake phytoplankton and zooplankton.
abstract: The increasing use of silver nanoparticles (AgNPs) in consumer products raises concerns regarding the environmental exposure and impact of AgNPs on natural aquatic environments. Here, we investigated the effects of environmentally relevant AgNP concentrations on the natural plankton communities using in situ enclosures. Using twelve lake enclosures, we tested the hypotheses that AgNP concentration, dosing regimen, and capping agent (poly-vinyl pyrrolidone (PVP) vs. citrate) exhibit differential effects on plankton communities. Each of the following six treatments was replicated twice: control (no AgNPs added), low, medium, and high chronic PVP treatments (PVP-capped AgNPs added continuously, with target nominal concentrations of 4, 16, and 64 μg/L, respectively), citrate treatment (citrate-capped AgNPs added continuously, target nominal concentrations of 64 μg/L), and pulse treatment (64 μg/L PVP-AgNPs added as a single dose). Although Ag accumulated in the phytoplankton, no statistically significant treatment effect was found on phytoplankton community structure or biomass. In contrast, as AgNP exposure rate increased, zooplankton abundance generally increased while biomass and species richness declined. We also observed a shift in the size structure of zooplankton communities in the chronic AgNP treatments. In the pulse treatments, zooplankton abundance and biomass were reduced suggesting short periods of high AgNP concentrations affect zooplankton communities differently than chronic exposures. We found no evidence that capping agent affected AgNP toxicity on either community. Overall, our study demonstrates variable AgNP toxicity between trophic levels with stronger AgNP effects on zooplankton. Such effects on zooplankton are troubling and indicate that AgNP contamination could affect aquatic food webs.
authors.affiliation: Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, Canada.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Vincent
authors.affiliation: IISD-Experimental Lakes Area, Winnipeg, MB, Canada.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Paterson
authors.affiliation: Department of Biology, Trent University, Peterborough, ON, Canada.
authors.forename: Beth C
authors.initials: BC
authors.lastname: Norman
authors.affiliation: Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO, USA.
authors.forename: Evan P
authors.initials: EP
authors.lastname: Gray
authors.affiliation: Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO, USA.
authors.forename: James F
authors.initials: JF
authors.lastname: Ranville
authors.affiliation: Department of Biology, Trent University, Peterborough, ON, Canada.
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Scott
authors.affiliation: Department of Biology, Trent University, Peterborough, ON, Canada.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Frost
authors.affiliation: Department of Biology, Trent University, Peterborough, ON, Canada. mxenopoulos@trentu.ca.
authors.forename: Marguerite A
authors.identifier: http://orcid.org/0000-0003-2307-948X
authors.initials: MA
authors.lastname: Xenopoulos
mesh_terms: D000818:Animals; D004781:Environmental Exposure / Q000032:analysis*; D060106:Lakes / Q000737:chemistry; D053768:Metal Nanoparticles / Q000633:toxicity*; D010839:Phytoplankton / Q000187:drug effects* / Q000502:physiology; D012834:Silver / Q000633:toxicity; D036401:Toxicity Tests, Chronic; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015048:Zooplankton / Q000187:drug effects* / Q000502:physiology
chemical_list: D014874:Water Pollutants, Chemical; D012834:Silver
keywords: Community structure; Enclosures; Experimental lakes area; Phytoplankton; Silver nanoparticles; Zooplankton