Saharan dust clouds travel thousands of miles and fertilize the water off the West Florida coast with iron, which kicks off blooms of toxic algae, according to a new study. The research was partially funded by a NASA grant as part of ECOHAB: Florida (Ecology and Oceanography of Harmful Algal Blooms), a multi-disciplinary research project designed to study harmful algae.
Toxic algal blooms, sometimes called red tides, have in the past killed huge numbers of fish, shellfish, marine mammals, birds, and can cause skin and respiratory problems in humans.
Each year iron from Saharan dust clouds is deposited in the waters off the West Florida coast. Once there, plant-like bacteria use the iron to set the stage for red tides. When iron levels go up, this bacteria, called Trichodesmium, 'fixes' nitrogen in the water, converting it to a form usable by other marine life. The addition of biologically usable nitrogen in the water makes the Gulf of Mexico a more likely environment for toxic algae to bloom.
"This is one of the first studies that quantitatively measured iron from the dust and tied it to red tides through Trichodesmium," said Jason Lenes, a graduate student at University of South Florida's College of Marine Science, and the lead author in the study. Lenes works under John J. Walsh, one of the principal investigators for ECOHAB, and one of the paper's coauthors. The research appears in the September issue of the scientific journal, Limnology and Oceanography.
Storm activity in the Sahara Desert region generates clouds of dust that originate from fine particles in the arid topsoil. Easterly trade winds carry the dust across the Atlantic Ocean and into the Gulf of Mexico. "Because iron is one of the most common elements in most soils, a certain percentage of the dust contains iron," said Lenes.
The study used satellite and ground based measurements to track large dust clouds leaving Africa on June 17, 1999. Lenes and his
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Contact: Cynthia M. O'Carroll
Cynthia.M.OCarroll.1@gsfc.nasa.gov
301-614-5563
NASA/Goddard Space Flight Center
28-Aug-2001