The copper-complexing capacity of seawater

The strong copper-complexing capacity of seawater varies over three orders of magnitude. High values are associated with high phytoplankton biomass. When the biomass is low, the copper-complexing capacity is low providedthat a moderate productivity (14C uptake) is sustained by a reliable source of nutrients. In such cases, the low biomass results from physical (deep mixing) or biological (heavy grazing) processes. In nutrient-limited, oligotrophic waters of low average productivity, the copper-complexing capacity is variable with occasional high values occurring. In the western Pacific, we found no evidence that water upwelling along the equator was conditioned by the production of organic ligands. These results also suggest that active grazing by herbivores does not release organic compounds into the water column.