Cadmium in the Coastal Upwelling Area Adjacent to the California – Mexico Border

Cadmium concentrations ([Cd]) were measured in samples from the water column of the coastal upwelling zone adjacent to the California – Mexico border. Temperature and nutrient distributions showed an intense upwelling event during our sampling. Lowest [Cd] were found at locations offshore (50 km) (0•03–0•058 nM), whereas the maximum concentrations were found inshore (0•14–0•166 nM). Both nutrients and [Cd] were enriched in coastal waters. Our inshore [Cd] values are about 25% of those reported for waters off central California. This is possibly due to the intrusion of oligotrophic waters from the eastern edge of the North Pacific Central Gyre to the Southern California Bight. Multivariate analysis indicates that high [Cd]s were associated with high phytoplankton biomass, nutrients and low temperature. Our data present no evidence of a [Cd] gradient due to the San Diego and Tijuana sewage discharges, which indicates that they maintain a very local effect.