MP8 Metals in the Environment: Dietary concerns in Aquatic Systems
Monday, 14 November 2005: 8:00 AM - 5:30 PM in Exhibit Hall

(PED-1117-834216) Waterborne and dietborne acute silver toxicity in the euryhaline copepod acartia tonsa.

Pedroso, M¹, Bianchini, A^{1, 2}, ¹ Programa de Pos Graduação em Ciências Fisiológicas - Fisiologia Animal Comparada, Rio Grande, RS, Brasil² Departamento de Ciências Fisiológicas, Rio Grande, RS, Brasil

ABSTRACT- Silver is a non-essential metal that is toxic to aquatic invertebrates, especially when they are exposed to waterborne silver. However, few studies have considered the importance of dietborne exposure on acute silver toxicity. The aim of this study was to determine the influence of natural food (Thalassiosira weissflogii 20,000 algae cells/ml) on the acute silver toxicity in the euryhaline copepod Acartia tonsa. Copepods were acclimated to salinity 5 or 30, for 1 week. Temperature and photoperiod were fixed at 20°C and 16L:8D, respectively. Food was pre-contaminated for 24 h with the same concentration of copper used in the waterborne exposure. Silver toxicity in either the absence or the presence of food was determined using a standard static-renewal system. Based on nominal silver concentrations, 48h-LC50 (g/L) with respective 95% confidence interval was 9.8 (6.22-14.72) g Ag/L at salinity 5 and in the absence of food. In the presence of food, copepod mortality and a decrease in the initial number of algae cells were not observed in concentrations up to 75 g Ag/L. However, higher concentrations induced a significant decrease in the initial number of algae cells. In salinity 30, 48h-LC50 was 163.2 (103.1-217.8) g Ag/L in the absence of food. In the presence of food, copepod mortality and a decrease in the initial number of algae cells were not observed in concentrations up to 10 g Ag/L. These results indicate that the presence of food pre-contaminated with silver at salinity 5 reduce silver toxicity in concentrations where a decrease in the initial number of algae cells is not observed. They also show that the algae Thalassiosira weissflogiiis more sensitive to silver than the copepod in both salinity 5 and 30.

Key words: acute silver toxicity, invertebrate, dietborne exposure, waterborne