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

Beth C Norman,Marguerite A Xenopoulos,Paul C Frost,Daniel Braun,Amitava Mukherjee

doi:10.1371/journal.pone.0129328

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.

Highlights

Nanotechnology is a growing and increasingly pervasive industry
AgNP exposure had significant effects on periphyton biomass and autotroph standing crop in L224 but these effects were different depending on the level of P enrichment (Fig 1a and 1d)
The higher Ag values recorded in periphyton from No-Ag substrates in L222 may have resulted from contamination during sample collection and processing

Summary

Introduction

Nanotechnology is a growing and increasingly pervasive industry. The use of silver nanoparticles (AgNPs) is prevalent due to their antimicrobial properties. These antimicrobial properties result partly from the release of ionic silver from the particulate form [1] and partly from interactions of the nanoparticles with cellular membranes and internal cellular structures [2]. Given the growing use of AgNPs in consumer products and the probability of their release into the environment [3], there continues to be a need to understand their effects on organisms and ecological interactions.

Methods

Results

Conclusion