Iron enters remote HNLC regions through two primary methods: upwelling of nutrient-rich water and atmospheric dust deposition. Iron needs to be replenished frequently and in bioavailable forms because of its insolubility, rapid uptake through biological systems, and binding affinity with ligands. Dust deposition might not result in phytoplankton blooms unless settling dust is in the correct bioavailable form of iron. Additionally, iron must be deposited during productive seasons and coincide with the appropriate RKR-ratios of surface nutrients. Aeolian dust has a larger influence on Northern Hemisphere HNLC regions because more land mass contributes to more dust deposition. Due to the Southern Ocean's isolation from land, upwelling related to eddy diffusivity provides iron to HNLC regions.