Effects of Chronic Dietary and Waterborne Cadmium Exposures on the Contamination Level and Reproduction of Daphnia magna

Abstract

Regulatory assessments of metal toxicity on freshwater organisms assume that toxic effects are caused by dissolved metals. In aquatic systems, organisms are exposed to both dissolved and particulate-bound metals. In this study, the chronic toxicity of dietary cadmium (Cd) on the reproduction and Cd body burden of Daphnia magna was investigated. Daphnids (Ͻ24 h) were successively exposed to dissolved Cd (8 h) and then to uncontaminated or contaminated algae (16 h) for 21 d. The results show a higher Cd burden in daphnids because of the addition of contaminated food and reveal that Cd uptake by D. magna from water and food was additive for the lowest Cd concentrations tested. Similar Cd distributions (cytosolic and insoluble fractions) were observed in the two groups of organisms, showing similar potential toxicity of Cd accumulated from the two exposure routes. Dietary Cd induces deleterious effects on D. magna reproduction. On the basis of Cd body burden of daphnids, the results support the claim that waterborne and dietary Cd exposures were additive in causing toxicity for Cd concentrations lower than 25 g/L. At the highest Cd concentrations, the importance of dietary Cd on the daphnid contamination level decreases and confounding factors such as feeding rate reduction seem to appear, which induce an effect on neonate reproduction. In this study, we illustrate the need to take the dietary pathway into account in regulatory assessments and to establish effective concentrations with particulatebound metals.

Effects of dietary cadmium exposure on reproduction of saltwater cladoceran Moina monogolica Daday: Implications in water quality criteria

“…to the values reported by some researchers [18]. However, these values were much lower than those obtained for Skeletonema costatum and Tetraselmis suecia, perhaps because the various algal strains have different exclusion mechanisms and detoxification processes when exposed to cadmium [19], which also produced different cadmium burdens of various algal species [20].…”

“…However, algae are not the only suspended solid-phase component found in natural waters. The suspended solids in the water are a mixed collection of different materials, resuspended sediment, colloids, fecal material, organic decomposition materials, etc., which can easily adsorb metals and could constitute a source of contamination and toxicity for aquatic organisms [20]. Moina monogolica usually feed on a mixed algal diet in the field.…”

Relating suborganismal processes to ecotoxicological and population level endpoints using a bioenergetic model

“…Studies on organismal response of D. magna demonstrate that exposure to Zn reduces feeding rate and also decreases mass, energy reserves, and neonate production in chronic exposures (Muyssen et al 2006, Poynton et al 2007). Exposure to Cd also reduces feeding rate (e.g., Bodar et al 1988a, Allen et al 1995, Knops et al 2001) and leads to reduced reproduction (e.g., Bodar et al 1988b, Geffard et al 2008. Figs.…”

Effects of Pollution on Freshwater Organisms

“…Geffard et al (2008) investigated the toxicity of dietary cadmium by exposing Daphnia magna to dissolved cadmium and then to contaminated and uncontaminated algae. The results indicated higher cadmium body burdens due to the addition of contaminated food.…”