PH08 Metals in the Environment: Aquatic Biological Perspectives
Exhibit Hall
8:00 AM - Thursday
(PH081) Avoidance to copper contamination by Daphnia longispina.
Lopes, I.1, Baird, D.1, Ribeiro, R.2, 1 Inst. do Ambiente e Vida, Univ. de Coimbra, Coimbra, Coimbra, Portugal2 Canadian River Institute, Department of Biology, Univ. New Brunswick, New Brunswick, Canada
ABSTRACT- In the past years, an intensive effort has been made to evaluate the ecological relevance of standard bioassays, namely through the development of cost-effective sub-lethal in situ assays, post-exposure feeding assays, and the comparison of sensitivities of standard test organisms and local species. Nevertheless, almost all terrestrial and aquatic assays that have been proposed involve the forced exposure of organisms to toxicants. If avoidance (sensu evasion) to contaminants occurs in real situations, then bioassays involving forced exposure can severely underestimate pernicious effects of contamination. Avoidance can have the same consequence as mortality (the disappearance of the population) at lower toxicant concentrations. Three main objectives were aimed in this study: 1) to develop a toxicity test to quantify avoidance by planktonic organisms to dissolved chemicals; 2) to verify if cladocerans presented genetically-determined avoidance behaviour to copper; 3) to determine the association between avoidance and other toxicity endpoints (lethality and feeding depression). Twelve cloned lineages of Daphnia longispina O.F. Muller, sampled from field populations, were selected accordingly to their sensitivity to lethal levels of copper and acclimated to controlled conditions for more than 30 generations. A 1.1-m test-chamber with five compartments was built, allowing the establishment of a dissolved toxicant gradient and the free movement of individuals. In the absence of any toxicant, juveniles from each cloned lineage distributed themselves randomly along the test-chamber, and, furthermore, no significant differences were observed between the two replicates, attesting the repeatability of this novel assay. All lineages showed significant avoidance to copper, when exposed to a gradient from 3 to 87 
g/L. Sensitive lineages started to avoid copper earlier than resistant ones. Avoidance was shown to be more sensitive than lethality and, even, than feeding depression. Therefore, avoidance assays should be recommended as a complementary tool in ecological risk assessments, and biomonitoring programs, since such assays can provide and ecologically relevant information.
Key words: Copper, Avoidance, Test development, Daphnia longispina