Effects of chronic sublethal exposure to waterborne Cu, Cd or Zn in rainbow trout 2: tissue specific metal accumulation

Tissue specific metal accumulations (gills, liver, kidney and whole body) i n rainbow trout (Oncorhynchus mykiss) were compared during chronic exposure (up to 100 days) to sublethal levels of waterborne Cd (3 mu g.l(-1)), Cu ( 75 mu g.l(-1)) or Zn (250 mu g.l(-1)) in moderately hard water (hardness of 140 mg.l(-1), pH 8.0). A general pattern of tissue metal increase and stab ilization was evident for all three metals, although the degree and time co urse of accumulation varied. The exception to this general pattern was a la ck of Zn accumulation in the liver and kidney although small amounts did ac cumulate in the gills and whole body. Accumulation of Cu occurred primarily in the liver while for Cd the kidney was the major organ of accumulation. Exponential modeling was employed to compare and contrast the saturation co ncentration and time to half saturation of various tissues. Accumulation of essential metals (Cu and Zn), if it occurred, was rapid and increases were relatively low. For example the time to half saturation during Cu exposure s was always less than 2 weeks and the maximum level of accumulation was le ss than four times background levels. For non-essential Cd, time to half sa turation for the liver and kidney was always longer than 5 weeks and modele d saturation concentrations were up to 80-fold higher than background. The response to Cu and Zn suggested an active regulation of tissue burdens whil e that of Cd appears to be more passive, resulting in continuous metal accu mulation over an extended time course. While the initial patterns of accumu lation for each metal were generally consistent with the damage, repair and acclimation pattern from concurrent physiological measurements it was clea r that tissue metal accumulation was not a good indicator of either exposur e of physiological impact. (C) 2000 Elsevier Science B.V. All rights reserv ed.