Illustration depicting sources of dissolved iron in seawater

Scientists have long thought the majority of the ocean's iron a key biological nutrient comes from atmospheric dust, with smaller inputs from terrestrial sediment and hydrothermal vent fluids. Although iron is soluble in low-oxygen conditions around vents and along continental margins, it was believed iron remained localized and didn’t contribute much to the overall iron content of the ocean. But a recent study led by WHOI researchers found that deep-ocean vents and sediments are a major source of dissolved iron in the central Pacific Ocean and that iron from these sources can be transported long distances. (Illustration by Jack Cook, © Woods Hole Oceanographic Institution)