Water quality for nickel: Tissue residue as biomarker of exposure and resistance

JORGE HERKOVITS, ROBERTO SERVANT AND CRISTINA S. PÉREZ-COLL

Jackson, Mississippi, EEUU

Simposio; Second International Symposiumon recent advancesin environmental health research; 2005

Jackson State University

  There is an increasing concern for the establishment of water quality criteria in order to protect wildlife and human health. In the case of Ni, concentrations between 2 and 10 ug/L are considered as uncontaminated fresh water. Amphibians at early life stages are very susceptible to a large number of physico chemical agents, including Ni. The main aim of this study was to evaluate the possibility to employ Ni tissue residue values as a biomarker of both low level exposure and the resistance to adverse effects in case of a challenge to toxic concentrations to this heavy metal. Bufo arenarum embryos were treated with three different low level concentrations of nickel chloride during 14 days. The exposures started with  2; 8 and 20µg Ni2+/L for each group and concentrations were gradually increased up to: 16 (A) ; 64 (B)  and 160 µg Ni2+/L (C) respectively. Control embryos (D)  were maintained in AMPHITOX solution. Ni tissue residue at 48, 96; 240 and 360 hr post exposures were determined with an atomic spectrophotometer. Batches of 10 embryos by triplicate providing from each low level condition plus controls were challenged to 10, 20 and 30 mg Ni2+/L evaluating lethality up till 10 days post treatment. The tissue residue values were for A:0.5; B: 2.1 and C: 3.62 ug/g embryo (ww) which represent  bioconcentration factors (BCF) of 31; 33 and 23 respectively. Nickel was not detected in D. As a general pattern, the survival of embryos challenged to toxic Ni concentrations was lower than in controls in all groups but the most adverse effects were obtained in the embryos pretreated with the higher Ni concentrations. Thus, Ni tissue residue values could be considered as a biomarker for both low level exposure and the resistance to adverse effects in case of a challenge to toxic concentrations to this heavy metal in amphibian embryos. Based on these results it seems convenient for water quality criteria to evaluate both tissue residue and the response of living organisms to challenge conditions in order to establish maximal limits of chemical agents for wildlife protection purposes.