Trace metal changes associated with age of marine vertebrates.

Concentrations of selected trace metals in feral populations of marine and coastal elasmobranchs, teleosts, birds, and pinniped mammals are clearly related to age. Regardless of species or tissues, all data for individual metals, except Mn, showed the following trends: increases in Cd, Pb, Hg, and Se with increasing age of the organism; and decreases in Cr, Cu, Fe, Ni, and Zn. For Mn, mammals showed an increase with age whereas birds and fish exhibited decreases. The biological implications of these observations are imperfectly understood at this time. Factors that may account, in part, for these trends include differential uptake at various life stages, reproductive cycle, diet, general health, bioavailability of different chemical species, metal-metal interactions, metallothioneins, critical body parts, and anthropogenic influences.