Sublethal effects of silver in zooplankton: Importance of exposure pathways and implications for toxicity testing

Abstract

In aquatic environments, organisms are exposed to contaminants via direct uptake from water and by trophic transfer. However, most toxicity tests only examine uptake via the dissolved phase. We compared the response of marine and freshwater crustacean zooplankton to silver following dissolved and food exposure. Silver, like other metals, concentrates in aquatic food chains and may exert toxicity. In standard solute exposure toxicity tests, Ag is toxic to zooplankton at concentrations of 400 nM for marine copepods and 100 nM for freshwater cladocerans, concentrations far greater than those in most waters. However, if Ag is accumulated from algal food, reproductive success decreases by >50% when algae are exposed to only 1 nM Ag in copepods and 0.5 nM Ag in cladocerans. These concentrations are within an order of magnitude of those found in contaminated estuaries. Following dietary exposure, decreased egg production and viability occur when tissue Ag concentrations increase three- to fourfold to 0.3 ppm in cladocerans and 0.5 ppm in copepods. Assimilated Ag depresses egg production by reducing yolk protein deposition and ovarian development. Our results indicate that ecologically relevant toxicity tests should consider sublethal effects of contaminants obtained from food since these effects cannot be predicted from exposures to only dissolved contaminants.

The influence of algal densities on the toxicity of chromium for Ceriodaphnia dubia Richard (Cladocera, Crustacea)

“…The food, represented by the algae, can act as a channel of metal contamination of cladocerans (Hook and Fisher, 2001) or can counteract metal toxicity, due to their ability to exude organic compounds that complex metal (Lombardi and Vieira, 2000). In addition, the algae contribute to the resistance of the organisms to toxic substances by improving their nutritional state (Chandini, 1989).…”

“…The concentrations of metal used to contaminate P. subcapitata were close to those that cause 50% inhibition of the growth of this algal species (Hook and Fisher, 2001). Neonates of C. dubia were exposed to reconstituted water and fed with three different densities of metal-contaminated P. subcapitata (low, medium and high: 1 x 10 4 cells.mL -1 , 1 x 10 5 cells.mL -1 and 1 x 10 6 cells.mL -1…”

L’écotoxicologie aquatique - comparaison entre les micropolluants organiques et les métaux : constats actuels et défis pour l’avenir

“…Il s'agit d'une hypothèse simplificatrice qui a peut-être sa raison d'être lorsque les concentrations métalliques aqueuses sont très élevées (toxicité aiguë), mais qui manque de fondement scientifique pour des conditions d'exposition chronique (FISHER et HOOK, 2002;HOOK et FISHER, 2001;MEYER et al, 2005). Heureusement, en parallèle au développement du BLM, d'autres chercheurs se sont penchés sur le transfert trophique des métaux, c'est-à-dire sur le rôle de la nourriture comme vecteur d'exposition aux métaux.…”

A graphene-organic composite as a fluorescent chemosensor for Ag+

“…Silver ions, however, can cause severe damage to both the environment and to humans [13,14]. As one of the most toxic heavy metals, surpassed only by mercury, silver ion has been assigned to the highest toxicity class [15]. Silver ions may damage bacteria, and inhibit their growth, thereby affecting their reproduction [16].…”