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Desert Saharan Dust was Key to the Formation of the Bahamas' Great Bank

First Posted: Jul 25, 2014 08:18 AM EDT
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What does the Sahara have to do with the Bahamas Islands? The both are integrally linked, according to a new study. Scientists have found that iron-rich Saharan dust from the desert may have provided the nutrients necessary for specialized bacteria to produce the island chain's carbonate-based foundation.

In order to learn a bit more about the formation of the islands, the researchers analyzed concentrations of two trace elements characteristic of atmospheric dust, iron and magnesium, in 270 seafloor samples collected along the Great Bahama Bank. The highest concentrations of these elements were located to the west of Andros Island, which is an area which has the largest concentration of white-sediment laden bodies of water produced by cyanobacteria.

"Cyanobacteria need 10 times more iron than other photosynthesizers because they fix atmospheric nitrogen," said Peter Swart, one of the researchers, in a news release. "This process draws down the carbon dioxide and induces the precipitation of calcium carbonate, thus causing the whiting. The signature of atmospheric nitrogen, its isotopic ratio is left in the sediments."

So where do the high concentrations come from? It's likely that they're from iron-rich dust blown across the Atlantic Ocean from the Sahara. This could actually explain the existence of the Great Bahama Bank, which has been built up over the past 100 million years from sedimentation of calcium carbonate. The dust particles also provide the nutrients necessary to fuel cyanobacteria blooms which can produce the carbonate whitings in the surrounding waters.

The findings reveal how even two regions across the ocean from one another can be linked. More specifically, it shows how the Bahamas were built with the help of the desert. This could have implications for studying nutrient cycling in the future.

The findings are published in the journal Geology.

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