Estandarizacion del bioensayo de toxicidad agudacon diplodon chilensis usando un toxico de referencia

Abstract

A wide range of species vulnerability to toxicans makes necessary to use a combination of different species in environmental toxicity assessment. Species specific bioassays are standarized to minimize variations in successive measurements. The freshwater bivalve molluscs Diplodon chilensis is a potential test species for toxicity bioassay based on its widespread and abundant populations in rivers and lakes of Chile and its ecological significance in the plancktonic community as a powerful filter feeder. A standardized procedure with D. chilensis is herein described followed by the method's calibration. Juveniles of this species were exposed to a concentration gradient of potassium dichromate (K2Cr2O7) as reference toxicant for 96 h. The measured effect was mortality. After eight successive estimations of the median lethal concentration (LC50.96h) a mean value ±SD of 20,4 ±3,3 mg L-1 was found. Intra laboratory precision, estimated by means of the variation coefficient (VC), was 16,2 % and the superior and inferior control limits for future LC50 values derived from the control chart were 27 and 17,1 mg L-1 respectively. This bivalve can then be used as test organism in ecotoxicity assessment increasing the diversity of species in environmental testing batteries, with the extra benefit of being a mollusc, zoological group poorly represented among freshwater testing animals in ecotoxicological bioassays.