Metal concentrations in fish otoliths in relation to body composition after laboratory exposure to mercury and lead

Juvenile sand gobies Pomatoschistus minutus, plaice Pleuronectes platessa, and sole Solea solea were exposed to high or low levels of mercury or lead for 45 d in the laboratory. Points on the otolith corresponding to the core (pre-treatment), the start of exposure, midway through the exposure, and the termination of exposure were sampled and analysed by laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS). There were significant increases in the metal content of the goby and sole otoliths after exposure to mercury or lead, and the differences between the treatment levels for each element were significant. Plaice otoliths showed Little increase in metal accumulation, and the difference between treatments was not significant. The relationship between exposure level, otolith metal concentration, and the metal concentration in fish muscle tissue was complex. In general, lead accumulated faster in the otolith and uptake was higher at low exposure levels. Mercury concentrations in fish tissue generally paralleled the concentration measured in the otoliths and the exposure level. Lead concentrations in fish otoliths were inversely related to tissue concentrations.