Lead sources to California sea otters: Industrial inputs circumvent natural lead biodepletion mechanisms

Lead levels (as Pb/Ca atom ratios) and stable isotopic compositions were measured in teeth of preindustrial and contemporary California sea otters ( Enhydra lutris) to determine if postindustrial changes had occurred in the magnitude and source of accumulated lead. Lead/calcium atom ratios ( x¯ ± SD) in teeth of some contemporary animals (110 ± 37 × 10 −8, n = 3) were significantly elevated compared to levels in other contemporary (13 ± 6.0 × 10 −8, n = 4) and preindustrial (7.3 ± 3.9 × 10 −8, n = 6) otters. The isotopic ratios ( x¯ ± 2σ x¯ ) revealed a change in the sources of accumulated leads, from natural continental-derived leads in the preindustrial animals ( 207Pb/ 206Pb = 0.820 ± 0.002) to industrial sources dominated by aerosol leads in the contemporary otters ( 207Pb/ 206Pb = 0.836 ± 0.003). The one exception was a contemporary Monterey Bay animal ( 207Pb/ 206Pb = 0.853), who contained lead derived from an industrial waste lead deposit in Monterey Harbor. These data establish distinguishable sources of lead assimilated by sea otters, and indicate that elevated exposures to some animals circumvented the natural biodepletion of lead through marine trophic pathways.