As Cd is quite toxic, the accumulation of a significant amount of the total cytosolic Cd in the HMW pool could have toxicological significance. Total Cd levels in these organisms, however, were very low when compared to Zn and Cu. As a consequence, the amount of Cd associated with the HMW pool represents less than 0.05% of the total metals in the pool. As for Zn, it appears that the HMW pool is saturated and excess Zn is effectively accumulated in the MT pool. A similar situation is suggested for Cu. These observations suggest that urchins are not being stressed by the ambient metal levels at the three stations.