Revista Chilena de Historia Natural 79 (4): 517-535, 2006
RESEARCH ARTICLE
Seasonal variability of cadmium in a coastal upwelling system off northern Chile (Mejillones
bay, 23º S)
Total and dissolved cadmium were measured from surface to 100 m water depth,
between June 2002 and April 2003, in Mejillones bay. Total and dissolved cadmium range concentration was 0.41-10.7 and 0.08-1.61
nM, respectively. Cadmium profiles and water structure were used to study seasonal variability patterns of this metal in this upwelling
system. Oceanographic conditions during this period correspond to a normal (non- El Niño) year. Water masses present in this bay
correspond to subantartic superficial water, subtropical superficial water and Equatorial subsuperficial water with different degree of
mixture and stratification during sampling period. Cadmium profiles showed a classic nutrient-type distribution. Whereas some
differences in this profiles could be attributed to a water masses mixing condition into the bay. Multivariate analysis indicates that
temporal cadmium variations were associated with chlorophyll-a concentration and temperature fluctuation, indicating that, at this
temporal resolution, phytoplanktonic biomass production is the principal factor controlling cadmium concentration in surface waters of
Mejillones bay. By other hand, in spite of cadmium being a redox-sensitive metal, any significant influence of dissolved oxygen on this
metal were founded, thus microxic condition of bottom water of Mejillones bay is not the principal factor that promotes cadmium flux to
the sediments. Cd/PO4 ratio is in agreement with normal values reported for the Chilean coast, and its low values, compared with the
northeast Pacific coast, can be explained either by the fact that PO4 is more efficiently removed than cadmium from the surface layer,
or that cadmium remineralization is occurring much faster than in the case of PO4.
Key words:
cadmium, upwelling
system, Mejillones, Chile
