1. Can they use rusted iron (since it is in the water)2. How does the iron keep from sinking since they live at the surface
Phytoplankton require a variety of essential nutrients, including iron, to fix carbon dioxide and fuel ocean food webs, but the oxidized form of iron, Fe(III), that prevails in the ocean is only sparingly soluble in oxygenated seawater. The solubility of iron is enhanced through chelation with organic ligands, and nearly all of the dissolved iron in seawater is bound to natural ligands. More details in link.
