Saharan dust is feeding oceanic life in the Bahamas
A groundbreaking study shows that sand rich in iron, a vital micronutrient, is feeding species thousands of miles from its source.
Published in the journal, Frontiers in Marine Science, research points to a change in the properties when dust blows westward from the Sahara into the Atlantic ocean. The greater the distance, the more these molecules become ‘bioreactive’ – available for organisms to consume.
Focusing on the so-called Sahara-Sahel Dust Corridor, which runs from Mauritania to Chad, total iron concentrations and concentrations of isotopes were measured at two locations in this region. A third site, 500km east of the Florida coast, also had sand sediment measured. The results showed that bioreactive iron depleted the further it travelled, and scientists believe this is caused by organisms using it up.
‘Rather than focusing on the total iron content, as previous studies had done, we measured iron that can dissolve easily in the ocean, and which can be accessed by marine organisms for their metabolic pathways,’ said Dr Jeremy Owens, co-author of the study and Associate Professor at Florida State University. ‘Only a fraction of total iron in sediment is bioavailable, but that fraction could change during transport of the iron away from its original source. We aimed to explore those relationships.
‘Our results suggest that during long-distance atmospheric transport, the mineral properties of originally non-bioreactive dust-bound iron change, making it more bioreactive. This iron then gets taken up by phytoplankton, before it can reach the bottom,’ added Dr Timothy Lyons, a professor at the University of California at Riverside and the study’s final author. “We conclude that dust that reaches regions like the Amazonian basin and the Bahamas may contain iron that is particularly soluble and available to life, thanks to the great distance from North Africa.’
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