In an interconnected world, sometimes the most surprising connections are hidden right before our eyes. Or rather, above our heads. Think about the Sahel, that vast swath of land that separates the Sahara from sub-Saharan Africa. An arid place, seemingly hostile to life. Yet, this barren landscape is playing a crucial role in sustaining life thousands of miles away, in the middle of theAtlantic Ocean. How? Through dust. Yes, you understood correctly: dust. That same dust that bothers us when we clean the house is fueling an entire Marine ecosystem. It is a story that challenges the imagination, a journey that crosses continents and oceans, and that shows us how complex and surprising our planet is.
A few days ago we talked about the project that someone wants to carry forward to make the desert green, and I expressed my doubts because its dust has its own ecological value: a news like this from the Sahel confirms it. It makes us reflect on how, sometimes, what we perceive as useless or annoying can actually play a fundamental role in the balance of our global ecosystem.
Iron: the key element of this story
Il Iron is a micronutrient essential for life. It enables vital processes such as respiration, photosynthesis and DNA synthesis. In today's oceans, the availability of iron is often a limiting resource. This means that increasing the flow of iron into the oceans can increase the amount of carbon fixed by phytoplankton1, with consequences for the global climate.
But how does iron get into the oceans? Through rivers, melting glaciers, hydrothermal activity and, above all, the wind. However, not all chemical forms of iron are “bioreactive,” that is, available for absorption by organisms from their environment.
“Here we show that iron bound to Saharan dust blown westward over the Atlantic has properties that change with the distance it travels: the greater this distance, the more bioreactive the iron is,” said Dr. Jeremy Owens, associate professor at the Florida State University and co-author of a new study on Frontiers in Marine Science (that I link to you here).
Sahel-Sahara and away, a journey of transformation
Owens and his colleagues measured the amounts of bioreactive and total iron in sediment cores taken from the bottom of the Atlantic Ocean, collected by theInternational Ocean Discovery Program (IODP) and its predecessors. The IODP aims to improve our understanding of climate and ocean changes, geological processes, and the origin of life.
The researchers selected four cores, based on their distance from the so-called Sahara-Sahel Dust CorridorThe latter extends from Mauritania to Chad and is known to be an important source of dust-bound iron for downwind areas.
Atmospheric Chemistry in Action
The results showed that the proportion of bioreactive iron was lower in the westernmost cores than in the easternmost ones. This implied that a correspondingly larger proportion of bioreactive iron had been lost to dust and presumably used up by organisms in the water column, so it never reached the bottom sediments.
“Our results suggest that during long-distance atmospheric transport, the mineral properties of the originally non-bioreactive iron bound to dust change, making it more bioreactive. This iron is then taken up by phytoplankton, before it can reach the bottom,” explained Dr. Timothy Lyons, professor at theUniversity of California at Riverside and final author of the study.
Sahel Dust and Ocean Nourishment, the Global Implications
This discovery has implications that go far beyond the Sahel and the Atlantic. It shows us how interconnected our planet's land and marine systems are. Dust reaching regions like the Amazon Basin and Bahamas It may contain particularly soluble and life-sustaining iron, thanks to its great distance from North Africa and therefore longer exposure to atmospheric chemical processes.
Yes, even the driest regions of our planet play a crucial role in sustaining global life. Let’s rethink the ecological value of places we might consider “useless” or “sterile.”
- In 10 words: Phytoplankton are microscopic photosynthetic aquatic organisms at the base of food chains. ↩︎
