Plankton generally thrive in areas of the ocean with sufficient concentrations of certain nitrogen compounds near the surface, where plankton live  Nevertheless, some areas, though rich in these nitrogen compounds, have few plankton  These areas have particularly low concentrations of iron, and oceanographers hypothesize that this shortage of iron prevents plankton from thriving
However, an experimental release of iron compounds into one such area failed to produce a thriving plankton population, even though local iron concentrations increased immediately
The iron compounds released into the area occur naturally in areas of the ocean where plankton thrive.