Interspecific comparison of cadmium and zinc contamination in the organs of four fish species along a polymetallic pollution gradient (Lot River, France)

The impact of cadmium (Cd) and zinc (Zn) discharges related to an old zinc ore treatment facility in the Lot River (France) was investigated in four f ish species (the chub: Leusciscus cephalus, the roach: Rutilus rutilus, the perch: Perca fluviatilis and the bream: abramis brama brama). The organism s were sampled in four stations along the polymetallic contamination gradie nt. Cd and Zn analysis were carried out in five organs (gills, posterior in testine, liver, kidneys and skeletal muscle) in order to highlight the pote ntial pathways of uptake, storage and elimination of metals. The results in dicate a very strong Cd contamination in fish collected downstream from the metal source. The kidneys have the highest cadmium concentrations, but the gills and the intestine, as exchange organs, present the largest variation s between the stations in close relation with the contamination gradient. C d concentrations measured in the liver vary only slightly among the samplin g stations. Unlike the trends observed for Cd, Zn levels in fish population s are strongly regulated and do not follow ambient Zn concentrations. The c oncentrations measured vary also according to fish species, for both Cd and Zn. This study shows that the trophic habits can explain the interspecific differences in Cd bioaccumulation. Zn levels observed for each species in non-contaminated populations also help to understand metal bioaccumulation patterns in polluted sites, suggesting that the determinism of interspecifi c differences is constitutive. (C) 2000 Elsevier Science B.V. All rights re served.