Ecotoxicity of nanosilver on cladocerans and the role of algae provision

Abstract

Silver nanoparticles (AgNPs) are applied in diverse industries due to their biocide and physicochemical properties; therefore, they can be released into aquatic systems, interact with environmental factors, and ultimately exert adverse efects on the biota. We analyzed AgNPs efects on Ceriodaphnia reticulata (Cladocera) through mortality and life-history traits, considering the infuence of food (Tetradesmus obliquus, Chlorophyceae) presence and concentration. C. reticulata was exposed to AgNPs in acute (absence and two algae concentrations plus fve AgNPs treatments) and chronic assays (two algae concentrations plus three AgNPs treatments). AgNPs did not afect algae focculation but increased Ag+ release, being these ions less toxic than AgNPs (as proved by the exposure to AgNO3). A reduction in AgNPs acute toxicity was observed when algae concentration increased. Acute AgNP exposure decreased C. reticulata body size and heart rate. The chronic AgNP exposure reduced C. reticulata molt number, growth, heart rate, and neonate size:number ratio, being these efects mitigated at the highest algae concentration. Increases in relative size and number of neonates were observed in AgNP treatments suggesting energy trade of. The increased Ag+ release with food presence suggests that the AgNP-algae interaction might be responsible of the decreased toxicity. Although algae reduced AgNP toxicity, they still exerted adverse efects on C. reticulata below predicted environmental concentrations. Since algae presence reduces AgNP efects but increases Ag+ release, studies should be continued to provide evidence on their toxicity to other organisms.