Date of Award
Master of Science (MS)
This study characterizes binary-metal mixture effects of cadmium (Cd2+) + zinc (Zn2+) and Cd2+ + nickel (Ni2+) on Daphnia magna. Although acute studies have shown protective Ni2+ (Traudt et al. 2016) and Zn2+ effects (Meyer et al. 2015) against Cd2+ toxicity, no study has fully characterized a protective effect on D. magna at several endpoints (survival, reproduction, growth, and accumulation) on a chronic study. In this study, the titration design was selected to characterize the 21 day (21-d) chronic effects of the binary-metal mixtures on survival, growth, reproduction, and metal accumulation in D. magna. Using this design, increasing concentrations of Zn2+ (10, 20, 40, 80, 120, 160 and 200µg/L) and Ni2+ (20, 40, 80, 100, 120, 140, and 160µg/L) were titrated against a constant concentration of 1.5µg/L Cd2+. A single-metal assay (Zn2+/Ni2+ alone), a Cd2+ alone treatment, and a control treatment were concurrently conducted for comparison. The results in this thesis demonstrate that Cd2+ alone was highly toxic to D. magna. In a mixture with Cd2+ and Zn2+, sublethal concentrations of 10 and 20µg/L Zn2+ were consistently insufficient to protect D. magna from chronic Cd2+ toxicity since Cd2+ toxic effects were observed on the survival, reproductive, and growth endpoints (Figs. 1, 2, 9), whereas mixtures containing 40, 80, and 120µg/L Zn2+ provided strong protective effects to D. magna at all the endpoints examined. Higher Zn2+ concentrations of 160 and 200µg/L exceeded the necessary concentrations needed to protect D. magna, and no protective effects were observed. In contrast, sublethal and moderate Ni2+ concentrations
of 20, 40, and 80µg/L were found to strongly protect D. magna from chronic Cd2+ toxicity, whereas higher Ni2+ concentrations (≥100µg/L) exceeded the necessary concentration needed to protect D. magna, and Ni2+ protective effects were absent. Interestingly, 1.5µg/L Cd2+ was found to be protective in the Cd2+-Ni2+ mixture containing 100µg/L Ni2+. Additionally, no concentration of Ni2+ or Zn2+ was found to provide complete protective effects to D. magna (i.e. 100% protective effects). Therefore, suggesting that no concentration of Zn2+ or Ni2+ used in this study, entirely outcompeted the binding of Cd2+ ions to the biotic ligand. Embryos analyzed for morphological alterations in both the Cd2+-Zn2+ and Cd2+-Ni2+ mixtures demonstrate severe developmental defects. The results of the present study are useful for development of environmental quality guidelines for metal mixtures.
Perez, Edgar Ramiro, "Chronic Toxicity of Binary Metal Mixtures of Cadmium-Zinc and Cadmium-Nickelon Daphnia magna" (2016). Master's Theses. 3268.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.
Copyright © 2016 Edgar Ramiro Perez