Copper uptake kinetics in diverse marine phytoplankton

We measured short-term uptake rates of copper using the gamma-emitting radioisotope Cu-67 in seven algal species in natural and artificial seawater. Cellular net uptake of Cu was typically rapid over periods of 2-20 min. Net uptake ceased after about 60 min. The most copper-sensitive species examined, Synechococcus sp., exhibited 2-3 orders of magnitude higher carbon and surface-area-normalized Cu-accumulation rates (46 mu mol Cu mol C-1 min(-1) and 1,100 zmol Cu mu m(-2) min(-1)) (zmol = 10(-21) moles) than those measured in diatoms, chlorophytes, a dinoflagellate, and a coccolithophore. Cu-accumulation rates for Thalassiosira weissflogii were three times faster in natural seawater than in EDTA-buffered artificial seawater containing an inorganic Cu concentration of 28 pmol L-1. Calculations showing that the diffusive flux of inorganic Cu was insufficient to account for observed short-term uptake rates suggest that some of the Cu bound to naturally occurring organic ligands is released through the rapid dissociation of those complexes in the cell's boundary layer.