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.

Addition of silver nanoparticles has no long‐term effects on natural phytoplankton community dynamics in a boreal lake

“…Diversity, total biomass, and total pigments also showed no correlation with total silver concentrations or particulate silver concentrations indicating a higher influence of natural variables. Similar to the results of a several week long, lake mesocosm study with AgNPs, at the longer temporal scale natural variability in our ecosystem outweighs any effects the AgNPs may be causing on algal communities (Vincent et al ). It is also possible that in both of these studies natural variables such as dissolved organic matter (DOM) and dissolved ions are helping to increase AgNP stability, which can decrease toxic effects to organisms such as algae (Sharma et al ).…”

“…We also did not account for the effect of AgNPs on other foodweb components, specifically zooplankton grazers which may be more susceptible to AgNPs than phytoplankton (Griffitt et al 2008). However, a lake mesocosm study at the IISD-ELA found that PVP-capped AgNPs only had subtle effects on the zooplankton community and that these effects had no impact the phytoplankton, so we feel this is likely the case for our study as well (Vincent et al 2017). Despite these limitations, we nonetheless provide strong evidence that phytoplankton communities do not respond to environmentally relevant concentrations of AgNPs at seasonal scales across 2 yr and that natural seasonal an climatic drivers exert stronger effects on community dynamics at longer time scales.…”

“…We calculated the NMDS of the reference condition points using 50 iterations of the data starting at randomized points to minimize stress. We placed a 95% confidence interval around the reference condition points and then plotted the experimental points on the same NMDS axes (White et al 2011). We determined points that fell outside of the confidence interval to be statistically different from those of the reference condition.…”

Toxicity, biotransformation and bioaccumulation of silver nanoparticles in laboratory conditions and aquatic ecosystems

“…Отже, НЧAg спричиняють вищу токсичність у природних екосистемах, ніж у лабораторних. Однак результати досліджень у природних середовищах доводять меншу токсичність НЧAg [26,27], що підкреслює важливість досліджень у природних середовищах.…”

Spatial and temporal trends in the fate of silver nanoparticles in a whole-lake addition study

“…<1 week) conducted in microcosms [ 9 , 19 ] and in larger mesocosms [ 20 ]. Over longer time scales ranging up to several weeks, AgNP fate has been studied in a wetland mesocosm [ 8 ], in mesocosms placed in a lake [ 21 – 24 ] and in an estuary [ 25 ]. In general, these studies in mesocosms and microcosms indicate that the concentrations of Ag + are low in the natural aquatic environment because of rapid binding to organic and inorganic ligands [ 20 , 21 , 25 ].…”