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(70-32) The Australian freshwater crayfish Cherax destructor (Clark) as a bioindicator of trace metal pollution. Khan, Shahnaz1, Nugegoda, Dayanthi*,1, 1 RMIT University, Melbourne, Victoria, Australia ABSTRACT- Trace metals enter freshwaters from natural and anthropogenic sources resulting in the exposure of aquatic organisms via water, sediment and food. The accumulation and depuration of two essential trace metals nickel (Ni) and iron (Fe) by the edible Australian freshwater crayfish C. destructor (Clark) was studied in the laboratory. Crayfish were exposed to a range of dissolved nickel and iron concentrations for 3 weeks to study metal accumulation after which they were placed in clean water for 2 weeks to study elimination of accumulated metals from the body tissues. Tissues were dissected, freeze-dried, acid digested and analysed by atomic absorption spectrophotometry for metals. Results show high concentrations of nickel and iron accumulated in the gills, hepatopancreas and exoskeleton. No nickel or iron was detectable in the white muscle of the crayfish. Results from the 2- week depuration study demonstrate that C. destructor depurates nickel at a high rate from contaminated tissues when exposed to uncontaminated water while the depuration rate for iron was low. The acute toxicity (96-h LC50) of the essential metals copper (Cu), zinc (Zn), Iron (Fe) nickel (Ni) and non-essential metal cadmium (Cd) to juvenile C. destructor was also determined. The toxicity of trace metals to juvenile C. destructor decreased in the order of: Cd>Cu>Ni> Zn >Fe. While it is possible to use the body tissues of C. destructor to detect nickel and iron contamination in Australian freshwaters, it is recommended that this species not be used as a biomonitor of nickel pollution because of its ability to depurate nickel. Furthermore juvenile C. destructor could be used in routine toxicity testing of trace metal contaminated waters. Key words: crayfish , trace metals, accumulation, toxicity |
