The Southern Ocean encircling Antarctica is rich in the nutrients nitrate, phosphate and silicon but phytoplankton growth is limited by the supply of iron which is a crucial ingredient of all organisms. Iron is highly insoluble in sea water, so, unlike the other nutrients, is quickly lost in sinking particles. Addition of trace amounts of iron to these waters, whether from natural sources (contact with land masses and via settling dust blown of the continents) or by artificial iron fertilization (from a ship releasing dissolved iron sulfate to the surface layer), results in rapid algal growth leading to development of phytoplankton blooms.
Not if Nualgi is used - the iron in Nualgi is stable in water for a very long time.
Nualgi has a silica base, this keeps the iron stable. The nano size particles of Nualgi remain dispersed in water for a long time.