Acute silver toxicity to Cnesterodon decemmaculatus (Pisces: Poeciliidae) in a river with extreme water-quality characteristics

María Victoria Casares, Laura Isabel de Cabo, Rafael Seoane, Oscar Natale

Resumen


A 96 h acute silver toxicity test was performed in order to determine silver toxicity (LC50) to a local fish species (Cnesterodon decemmaculatus) in a river with extrem water-quality characteristics (Pilcomayo River, South America)    and evaluate a cross-fish-species extrapolation of the Biotic Ligand Model. The dissolved silver concentrations tested were 0.095, 0.148, 0.175 and 0.285 mg Ag L1. The 96 h Ag LC50 calculated for C. decemmaculatus was 0.14 mg L1 (0.18 - 0.10)  and the value predicted by BLM for Pimephales promelas was 0.051 mg Ag L1. Test water elevated hardness may have exerted some protective effect. High mean water pH may have exerted a major protective effect by reducing silver free ion form and causing silver precipitation. The mortality pattern observed in this toxicity test may lend some support to a relationship between gill silver accumulation and mortality. A cross-fish-species extrapolation of Ag BLM for  P. promelas was not valid in Pilcomayo River water and experimental conditions of this toxicity test.

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Acta Toxicológica Argentina ISSN 0327 9286 (impreso) - ISSN 1851-3743 (en línea). Alsina 1441, Of. 302, (CP 1088), C.A.B.A. www.ataonline.org.ar