Saharan fish dust fertilizes Amazon rainforests

BBC : Although the rainforests of the Amazon have long been fertilized by dust originating in the Sahara, the composition of that dust had not been extensively studied. Now Karen Hudson-Edwards of Birkbeck, University of London and colleagues show that one of the dust’s key nutrients, phosphorus, comes from the bones and scales of fish and other organisms that lived thousands of years ago in Megalake Chad . When they died, they sank to the bottom of the lake, which dried up and created a vast, dry dustbowl called the Bodélé Depression , the world’s greatest single source of dust. Strong surface winds regularly sweep across the area and carry millions of tons of dust across the Atlantic Ocean every year. By examining the crystalline structure of the apatite mineral found in the dust, the researchers determined that it came not from the weathering of rock but from once-living organisms. That type of phosphorus is more readily soluble and is commonly used in soil fertilizers. Hence, it is extremely important for maintaining the health of the Amazon rainforest. However, the Bodélé dust won’t last forever, and the researchers plan to look into precisely how long the essential material can be sustained.