Use of bacterial bioluminescence (Microtox test) as a tool for assessing the toxicity of pure substances and complex effluents (Moroccan Atlantic coast)

The Microtox test is a rapid, simple, and widely used test in the context of screening and comparative studies. The aim of this study is to use the Vibrio fischeri bacteria luminescence inhibition test to assess the toxicity of metals and those of industrial unit discharges. The assessment of the effects of discharges on V. fischeri luminescence reveals the great sensitivity of this bioindicator to discharges and highlights a high risk of deterioration in the quality of the marine environment, particularly in the areas where discharges, with EC50s which can reach 0.25% discharge into the test medium for petrochemical effluents after 5 minutes of exposure. The analysis of these results made it possible to classify the discharges according to their toxicity towards the bacterium V. fischeri and to draw up a profile of the impact of these discharges according to the EC50 values. The results of tests carried out on metals show that mercury is the most toxic metal (EC50 = 0.63 mg Hg L-1), followed by lead (EC50 = 1.08 mg Pb L-1) and cadmium (EC50 = 1.87 mg Cd L-1) and finally copper (EC50 = 2.57 mg Cu L-1). The results obtained during this study show that the Microtox test represents a good model for evaluating the toxicity of complex discharges and pure substances and that bacterial luminescence constitutes an excellent bioindicator for screening the medium quality.