Persistent winds across the Sahara lift sand into the atmosphere, causing it to travel towards the USA and the Caribbean. According to a team led by Peter Swart of the University of Miami, this dust is responsible for the existence of the Great Bahama Bank, which built up over the past 100 million years. The dust particles, the team contends, provided the nutrients necessary to fuel cyanobacteria blooms, which in turn, produced the calcium carbonate sediment that makes up the bank.
Swart and his team collected 270 seafloor samples along the Great Bahama Bank over a three-year period and then measured the concentrations of two trace elements characteristic of atmospheric dust – iron and manganese. They found the highest concentrations in samples collected to the west of Andros Island. This area has the largest concentration of so-called whitings – white sediment-laden bodies of water that are produced by photosynthetic cyanobacteria.
‘Cyanobacteria need ten times more iron than other photosynthesisers because they fix atmospheric nitrogen,’ said Swart. ‘This process draws down the carbon dioxide and induces the precipitation of calcium carbonate, thus causing the whiting.’