Monitoring of Labile Zinc in Cultures ofSkeletonema costatumUsing a Salt Groundwater

Labile Zn concentration was monitored by differential pulse anodic stripping voltammetry (DPASV) throughout the exponential growth phase of the marine diatomSkeletonema costatum(Grev.) Cleve. Algal blooms were induced both under natural conditions and in laboratory experiments using a salt groundwater (salinity 33) from the Bay of Bourgneuf, northwest coast of France. Salt groundwater is a very complex medium containing high concentrations of dissolved organic matter and other trace metal adsorbents, such as phosphate, iron oxyhydroxides, and manganese and silicon oxides, which can bind metal ions, reducing their availability and toxicity to algae. Besides metal uptake by algae and complexation of Zn by algal exudates, the rapid decrease in the labile Zn concentration during the algal blooms was ascribed mainly to the adsorption or coprecipitation of Zn ion onto freshly formed iron hydroxides.