Comparison of river and coastal water as potential sources of bioavailable iron

The assimilation of dissolved iron by phytoplankton depends on its chemical speciation and/or oxidation state. In this study river and coastal water was irradiated with a sunlight simulator and monitored for photoproduction of bioavailable reduced iron using a colorimetric method. The 0.01 μΜ steady-state concentration of ferrous ion was detected in river water during irradiation. The apparent quantum yield, an estimate of process efficiency, suggests qualitative differences between organic iron complexes in river and coastal water. The amount of photoproduced bioavailable iron may be of importance in relieving iron stress in potentially toxic diazotrophs in the area affected by the river plume.