Bioavailability and Chronic Toxicity of Zinc to Juvenile Rainbow Trout (Oncorhynchus mykiss):  Comparison with Other Fish Species and Development of a Biotic Ligand Model

Abstract

In this study, the effects of modifying Ca (0.2-4 mM), Mg (0.05-3 mM), Na (0.75-5 mM), and pH (5.5-7.5) on the chronic toxicity of zinc to juvenile rainbow trout (Oncorhynchus mykiss) were investigated using standard 30-d assays in which survival and growth were monitored. Survival was observed to be a more sensitive end point than growth, and mortality mainly occurred during the initial stages of the exposure. This suggested that the mode of action of zinc toxicity was mainly of an acute nature. A review and analysis of existing literature demonstrated similar results for most other fish species investigated. Overall, up to a 30-fold variation of zinc toxicity was observed, as indicated by no observed effect concentrations varying between 32.7 and 974 microg of Zn L(-1). Increased concentrations of Ca2+, Mg2+, Na+, and H+ (within the tested ranges) resulted in a reduction of chronic zinc toxicity by a factor of 12, 3, >2, and 2, respectively. This suggests the major importance of Ca competing with zinc and protecting against zinc toxicity, which seems to be a ubiquitous concept in fish species (and probably also invertebrate). On the basis of the toxicity data obtained, a chronic biotic ligand model (BLM) was developed that takes into account both chemical speciation of zinc and competition between zinc and the above-mentioned cations. The developed model was able to predict chronic effect concentrations with an error of less than a factor of 2 in most cases. Hence, it was concluded that the chronic Zn BLM can reduce toxicity variability due to bioavailability to a considerable extent and that the BLM can become an important tool in criteria setting and risk assessment practice of zinc and zinc substances.

Effect of zinc toxicity on liver histology of Nile tilapia, Oreochromis niloticus

“…Also, Shetty Akhila et al (2007) reported that the determination of acute toxicity is usually an initial screening step in the assessment and evaluation of the toxic characteristics of all compounds. Likewise, De Schamphelaere and Janssen (2004) reported that fish mortality might be a more sensitive endpoint for assessing effect of Zn exposure.…”

Evaluation Of The Biotic Ligand Model For Predicting Metal Bioavailability and Toxicity In SRS Effluents And Surface Waters

“…Interestingly, the protective actions of Na + seemed to be similar in the chronic model and Janssen, 2004d). Furthermore, a chronic Zn-BLM has also been developed for fish (De Schamphelaere and Janssen, 2004c), and its similarity to the acute Zn-BLM in the dominant protective role of Ca 2+ in predicting mortality (the most sensitive endpoint in the chronic history) again suggest that the acute and chronic toxic mechanisms of zinc in fish are similar (i.e., disruption of Ca 2+ homeostasis). In case of silver also, the mechanism does appear similar (Na + balance pathology).…”

Germanium and indium

“…For example, in toxicity tests with aquatic invertebrates incubated with lead-zinc mine tailings from the Tri-State mining district, Besser and Rabeni (1987) showed that increased concentrations of dissolved cadmium, lead, and zinc correlated with decreased survival and growth (Besser and Rabeni, 1987). Likewise, various fish species experienced rapid mortality when exposed to increasing dissolved zinc concentrations, but this effect decreased with increasing calcium, magnesium, and sodium concentrations (De Schamphelaere and Janssen, 2004). High metal concentrations in soils can also cause phytotoxicity.…”