Phosphorus Availability Alters the Effects of Silver Nanoparticles on Periphyton Growth and Stoichiometry

Abstract

Exposure to silver nanoparticles (AgNPs) may alter the structure and function of freshwater ecosystems. However, there remains a paucity of studies investigating the effects of AgNP exposure on freshwater communities in the natural environment where interactions with the ambient environment may modify AgNP toxicity. We used nutrient diffusing substrates to determine the interactive effects of AgNP exposure and phosphorus (P) enrichment on natural assemblages of periphyton in three Canadian Shield lakes. The lakes were all phosphorus poor and spanned a gradient of dissolved organic carbon availability. Ag slowly accumulated in the exposed periphyton, which decreased periphyton carbon and chlorophyll a content and increased periphyton C:P and N:P in the carbon rich lakes. We found significant interactions between AgNP and P treatments on periphyton carbon, autotroph standing crop and periphyton stoichiometry in the carbon poor lake such that P enhanced the negative effects of AgNPs on chlorophyll a and lessened the impact of AgNP exposure on periphyton stoichiometry. Our results contrast with those of other studies demonstrating that P addition decreases metal toxicity for phytoplankton, suggesting that benthic and pelagic primary producers may react differently to AgNP exposure and highlighting the importance of in situ assays when assessing potential effects of AgNPs in fresh waters.

Engineered nanoparticles interact with nutrients to intensify eutrophication in a wetland ecosystem experiment

“…We expected to observe significant effects of AuNP on wetland autotrophs, as AuNPs have been found to induce toxicity and to be bioavailable for different model organisms (Barrena et al 2009, Sabo-Attwood et al 2012, Tsyusko et al 2012, Glenn and Klaine 2013. We anticipated significant treatment interactions between nutrient enrichment and both NPs, as previous studies have reported interactive effects of nutrient enrichment and pollutants on algal and periphyton stoichiometry and on macrophyte growth (Fulton et al 2009, Das et al 2014, Norman et al 2015. However, the direction of this interaction was difficult to predict as nutrient availability may either compensate for or enhance the impact of metal pollution on aquatic primary producers (Gessner and Tlili 2016).…”

“…, Norman et al. ). The deleterious effects of synthetic chemicals may be amplified under high nutrient loads due to increased uptake rates and faster transfer of the contaminants through exposed food webs (Berglund ).…”

“…, Norman et al. ). However, the direction of this interaction was difficult to predict as nutrient availability may either compensate for or enhance the impact of metal pollution on aquatic primary producers (Gessner and Tlili ).…”

“…There is growing evidence that our failure to examine the interactions between nutrient and other synthetic chemical pollutants may be compromising our understanding of impaired aquatic ecosystems. For instance, two studies found that phosphorus availability modulated the response of phytoplankton and periphyton communities to silver nanoparticles in lakes, leading to a reduction of the contaminant toxicity for pelagic primary producers and an increased toxicity for the benthic communities (Das et al 2014, Norman et al 2015. The deleterious effects of synthetic chemicals may be amplified under high nutrient loads due to increased uptake rates and faster transfer of the contaminants through exposed food webs (Berglund 2003).…”

Physical and chemical characterization of natural and modified nanoclays and their ecotoxicity on a freshwater algae species (Chlamydomonas reinhardtii)

“…Others have also emphasized the important role of aggregation for the production of toxic effects on algae by other types of NMs (Fleischer et al ; Madigan et al ; Navarro et al ; Oh and Park ). Furthermore, the low zeta potential for Cloisite 30B (–11 mV) could also result in important nutrients (e.g., phosphorus) binding to the nanoclay, which then limits the amount of nutrients available to algae (in part because the bound nutrient is now too large to pass through the pores of cell walls; Xiu et al ; Norman et al ). Differences in the ability of nanoclay type to form aggregates could also result in nanoclays having different toxic effects on benthic and pelagic organisms.…”