PARENT SESSION
26 - Metal Pollution: From Exposure to Ecological Effects (1)
8:30 AM to 12:20 PM, Tuesday, 14 May 2002
Session Chair: Janssen, Colin ¹, Gerhardt, Almut ¹, ¹ .
Strauss C

(26-08) Sodium turnover rate determines sensitivity to acute copper and silver exposure in freshwater animals.

Grosell, Martin^*,1, Nielsen, Claus¹, Bianchini, Adalto², Wood, Chris³, ¹ August Krogh Institute, University of Copenhagen, Copenhagen, Denmark² Fundação Universidade, Fedaral do Rio Grande, Rio Grande, Brazil³ McMaster University, Department of Biology, Hamilton, Ontario, Canada

ABSTRACT- We present a comprehensive review of the physiological mechanisms of acute copper and silver toxicity in freshwater organisms. Both metals result in inhibition of branchial sodium (and chloride) uptake initiating a cascade of effects leading to mortality. The inhibition of the branchial Na/K-ATPase in the basolateral membrane is generally accepted as the key component responsible for the reduced sodium uptake. In addition, branchial carbonic anhydrase and the apical sodium channel may also be important targets for both copper and silver exposure. Several attempts have been made to predict metal sensitivity. A prominent example is the geochemical biotic ligand model (BLM), which is gaining acceptance in North America. The geochemical biotic ligand modelling approach has been succesful in explaining variations in tolerance to metal exposure for specific groups of animals exposed to metals at different water chemistry. This approach, however, cannot explain the large observed variation in tolerance to these metals amongst different groups of freshwater animals (Daphnia versus fish). Based on the detailed knowledge of physiological responses to acute metal exposure, this presentation will offer an explanation for the observed variation in tolerance. The explanationis based on the fact that organism size is related to reported LC50 values and that organism size is related to sodium turnover rates. We thus present a way to improve predictions of acute metal sensitivity, an approach which could be easily integrated into the BLM, one, which is based on sodium turnover rate as the key predictor for variation in acute copper and silver toxicity amongst groups of freshwater animals. (Supported by NSERC, Kodak Canada, ICA, SNF, Carslberg Foundation).

Key words: copper, silver, freshwater organisms, sodium homeostasis