Comparison of ecotoxicological and physico-chemical data by use of multivariate analyses and graphical displays

Bioassays allow the appreciation of the toxicity of complex effluents, which is difficult to characterize by the sole measurement of some physico-chemical parameters. We have developed a macroinvertebrate multi-test (M.M.T.) with species characteristic of different trophic levels in order to appreciate the ecotoxicological impact of various effluents (especially landfill leachates) and chemicals on aquatic environments. Our aim was: (i) to compare the sensitivity of the macroinvertebrates among themselves and with regard to those of three standard bioassays; (ii) to characterize the effluents according to their toxicity on one hand and according to their physico-chemical composition on the other hand; (iii) to search for possible correlations between the physico-chemical composition of an effluent and its toxicity. In order to achieve these objectives we used first a combination of graphical displays of the raw data, and secondly multivariate analyses: clustering techniques and scaling (ordination) techniques (Principal Components Analysis).