REAL-TIME BIOMONITORING OF WATER CONTAMINATION BY CYANIDE BASED ON ANALYSIS OF THE CONTINUOUS ELECTRIC SIGNAL EMITTED BY A TROPICAL FISH - APTERONOTUS ALBIFRONS

A new early warding system for monitoring the quality of water was dev eloped using the information conveyed by the continuous electric organ discharges of the tropical fish Apteronotus albifrons (Gymnotiformes, family Apteronotidae). The principle is based on the time characteris ation of the electric signal emitted by the fish and uses the fact tha t the frequency and the form of the signal vary as a function of the p hysico-chemical quality of the ambient water. Eight test fish were ind ividually confined in a heat-proof test chamber in which a continuous water current, thermo-regulated at 27 degrees C, was maintained. The e lectric signal sampled over 1 a periods were amplified. The computer p rocessed the signals and their frequencies and determined the coordina tes of the points where the temperatures were recorded. The results of the A. albifrons electrical activity were then visualised on a visual display unit. Subsequent mathematical processing helped to detect unu sual electrical behaviour (crossing of lower and upper bounds). To ill ustrate the principle of this new early warning system, the electric r esponse of the A. albifrons exposed to cyanide was tested and compared with the detection thresholds of other biological early warning syste ms. A. albifrons is able to detect a cyanide concentration of 34.6 mu g l(-1) in less than half an hour. The recorded results suggest that t his new biomonitor corresponds very well with the requirements of warn ing stations for surface waters subject to cyanide pollution. Copyrigh t (C) 1996 Elsevier Science Ltd