Vast dust clouds originating from Africa are making their way across the Atlantic and through the Caribbean and US to Bermuda.

And scientists are seeking to determine which bacteria, fungi and viruses are hitchhiking with the dust and what effect they may have on living organisms where they end up.

Scientists with the US Geological Survey Center for Coastal Geology (USGS) in St. Petersburg, Florida, said the first small samples of dust from air over the US Virgin Islands are carrying contaminants that could play a role in triggering asthma in the US and Caribbean nations, where the rate of respiratory illness is high, the Associated Press reported.

And USGS marine geologist Eugene Shinn said the dust was linked to the demise of certain Caribbean corals and might be linked to the presence of mercury in the Everglades, Red Tide outbreaks along the coasts and disease in some amphibians.

There is nothing new about clouds of dust blowing westward across the Atlantic. The prevailing winds that guide the dust clouds are the same "trade winds'' that drove early exploration vessels and cargo ships and still blow hurricanes toward US and Caribbean shorelines every year.

A long drought in the Sahel grasslands near the Sahara in Northern Africa has caused huge and more frequent dust storms in recent years. Hundreds of millions of tons of soil are being blown away every year, scientists estimate.

Bermuda Biological Station for Research director Anthony Knap said viruses were likely carried in the winds but what diseases were carried and what effect they had on humans, animals and plants was not known yet.

The atmosphere played a huge role in the transportation of material, he continued, and this was one of the areas being looked at by the Station's Centre for Ocean and Human Health.

Dr. Knap said the first theories surrounding dust transport were developed from research conducted in the 1960s and 1970s at Bermuda's own Tudor Hill.

He said Bermuda received dust particles in the wind that originated in Africa, particularly from the Sahara, and followed the trade winds past Barbados and into the weather area known as the Bermuda High before being deposited on and around the Island.

Other dust sources for the Island included areas of the US at different times of the year, added Dr. Knap, and the amount of airborne particles depended upon the aridity of the region they came from.

The Tudor Hill study began looking at contaminant transport in 1974 through a project called the Western Atlantic Ocean Experiment which was funded by the US government, he said.

What was known, Dr. Knap added, was that amongst the dust blowing in from Africa was a large amount of iron -- an essential micro-nutrient required for plankton to grow.

And plankton is responsible for taking up large amounts of carbon dioxide from the atmosphere.

High concentrations of iron prompted more plankton growth which, in turn, encouraged more carbon dioxide absorption, said Dr. Knap.

However the dust also increases the cloudiness of the ocean, he continued, which affects light levels. Lower light levels cause the algae growing amongst the corals to die and this is believed to cause coral bleaching and degradation of reefs.

HEALTH HTH