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

(70-48) The influence of zinc acclimation on tolerance and population dynamics of algae and daphnids: an overview.

Muyssen, Brita^*,1, Janssen, Colin, ¹ Ghent University, Laboratory of Environmental Toxicology and Aquatic Ecology, J. Plateaustraat 22, Ghent, Belgium

ABSTRACT- All essential elements including zinc have an optimal concentration range bounded by deficient or toxic concentrations. Deficient and optimal ranges have been established for only a limited number of species. Acclimation to essential and non-essential metals may cause sensitivity shifts, but until present the influence of acclimation to low concentrations of essential elements has not been investigated. The integration of essentiality and acclimation and the influence on the ecological risk assessment of essential metals was the subject of the present study. Therefore, we acclimated Raphidocelis subcapitata, Chlorella vulgaris (green algae), Daphnia magna (laboratory and field populations) and Ceriodaphnia dubia (both Cladocera) to a range of zinc concentrations. Acclimation induced increases in zinc tolerance were up to a factor of 4. For the field-collected D. magna populations it could not be elucidated if this was due to acclimation or interclonal variation. For D. magna an optimal concentration range from 2 to 22 g Zn²⁺/L was demonstrated. Organisms cultured at these concentrations were significantly larger and exhibited increased reproduction rates and energy budgets. We demonstrated that zinc was actively regulated up to a body concentration of 150 g/g DW. For the algae, 40 g Zn²⁺/L was more optimal than 0.03 g Zn²⁺/L (deficient) and for C. dubia, survival and reproduction was higher in organisms cultured in 0.08 and 0.2 g Zn²⁺/L than those reared in 0.004 and 0.2 g Zn²⁺/L . Concerning the consequences for risk assessments it can be concluded that shifts in tolerance due to acclimation are relatively low, especially within environmentally relevant acclimation concentrations, but nevertheless more attention should be paid to the culturing conditions before testing when evaluating toxicity data used for these risk assessments.

Key words: acclimation, zinc, daphnids, risk assessment