Abstract To assess the magnitude of metal levels of the Blanca bay seawater and to evaluate future potential changes due to anthropogenic activity, the seasonal and spatial variations of both dissolved and total copper, cadmium and zinc, as well as temperature, salinity, pH, suspended matter and particulate carbon were measured in 114 samples taken between April 1980 and April 1981. All parameters measured showed seasonal variations, with similar patterns for all metals, suspended matter, particulate carbon and nutrients. Both dissolved and total copper and cadmium concentrations showed increased seawards, originating from progressive contaminant inputs to the bay. Zinc, pH, temperature and particulate carbon showed nearly uniform levels throughout the Blanca bay. Salinity was found to increase seawards due to dilution effects of freshwater inputs. The major percentage of metals were present as dissolved fractions, and part of these were associated with organic matter. The average levels for metals found in seawater from the Blanca bay were higher than average values found in geographical areas not affected by anthropogenic inputs, but most of the levels were comparable with data reported for contaminated regions.