Short-term and long-term uptake of zinc by the mussel, Mytilus edulis: a study in individual variability.

Abstract

In previous studies, the zinc concentration of the whole soft tissue of the musselMytilus edulis showed a high degree of unexplained residual variability which could not be accounted for by any known ecological or physiological factors. This high variability was almost entirely due to the unusually high degree of variability in kidney zinc concentrations (range 97-7,864 μg/g; n=561). In the present study, unfed mussels were exposed to natural levels of zinc (labelled with zinc-65) in clean seawater in a laboratory aquarium. In spite of the environmental homogeneity in the laboratory environment, the kidney showed a high coefficient of variation (around 70%) for zinc-65 concentrations after 66 days of exposure to the radioisotope. Other tissues showed only low coefficients of variation (10–30%). This suggested that the high variability of kidney zinc was not a result of unknown ecological factors (differences in microhabitat), but was due to biochemical differences between individual mussels. In a second experiment, it was noted that the zinc-65 and stable zinc concentrations of the kidney showed significant positive correlation after only six days exposure to zinc-65, indicating that the factors leading to the high variability of zinc in the kidney were operative within the first few days after uptake. Hence, kidney zinc variability appeared more likely to be the result of short-term processes (zinc uptake, elimination of zinc from short term compartments) than long-term processes (granule excretion). Female mantle had a higher stable zinc concentration but a lower radio-zinc concentration than male mantles. The radio-zinc concentration of the mantle's edge was greater than that of the mantle without an edge. MSRL Contribution Number 701