PARENT SESSION
70 - Metal Pollution: From Exposure to Ecological Effects
8:00 AM to 6:30 PM, Wednesday, 15 May 2002
Exhibition Area

(70-47) Effects of multi-generation acclimation to environmentally relevant zinc concentrations on zinc tolerance in Daphnia magna.

Muyssen, Brita^*,1, Janssen, Colin¹, ¹ Ghent University, Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent, Belgium

ABSTRACT- Most metal acclimation studies with daphnids focus on relatively high metal concentrations and short acclimation periods and use acute toxicity as evaluation criterion for tolerance change. Moreover, metal bioavailability and essentiality are often neglected. In the present study Daphnia magna was acclimated for six generations to an acclimation range of 0.02 to 74 g/L Zn²⁺. This concentration range represents the natural Zn background of bioavailable Zn in European surface waters and was derived by measured concentrations and speciation models. No significant differences in acute or chronic Zn tolerance (48h- and 21d-EC50, respectively) were found between the different acclimation treatments. Nevertheless, at test concentrations below the 21-dEC50, acclimation did have significant effects on net reproductive rates. Organisms acclimated to 6 to 22 g/L Zn²⁺ produced significantly more offspring than organisms acclimated to lower and higher Zn concentrations in test concentrations up to 50 g/L Zn²⁺ and therefore this range can be considered as optimal for D. magna. This optimal concentration range corresponds to a previously established range, obtained in a different culture and test medium.

Key words: acclimation, zinc, Daphnia magna, essentiality