Iron is a micronutrient indispensable for life, enabling processes such as respiration, photosynthesis, and DNA synthesis. Iron availability is often a limiting resource in today's oceans, which means that increasing the flow of iron into them can increase the amount of carbon fixed by phytoplankton, with consequences for the global climate. Iron ends up in oceans and terrestrial ecosystems through rivers, melting glaciers, hydrothermal activity, and especially wind. But not all its chemical forms are "bioreactive," that is, available for organisms to take up from their environment. "Here we show that iron bound to dust from the Sahara blown westward over the Atlantic has properties that change with the distance traveled: the greater this distance, the more bioreactive the iron," said Dr. Jeremy Owens, an associate professor at Florida State University and a co-author on a new study in Frontiers in Marine Science. "This relationship suggests that chemical processes in the atmosphere convert less bioreactive iron to more accessible forms." Owens and colleagues measured the amounts of bioreactive and total iron in drill cores from the bottom of the Atlantic Ocean, collected by the International Ocean Discovery Program (IODP) and its earlier versions. IODP aims to improve our understanding of changing climate and oceanic conditions, geological processes, and the origin of life. The two cores closest to this corridor were collected approximately 200km and 500km west of northwestern Mauritania, a third in the mid-Atlantic, and the fourth approximately 500km to the east of Florida. The authors studied the upper 60 to 200 meters of these cores, reflecting deposits over the last 120,000 years - the time since the previous interglacial. They measured the total iron concentrations along these cores, as well as concentrations of iron isotopes with a plasma-mass spectrometer. These isotope data were consistent with dust from the... |