Nutrients in Dust from the Sahara Desert cause Microbial Blooms on the East Coast of the United States

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Saharan dust nutrients, particularly iron, deposited episodically in tropical marine waters stimulate marine microbial bloom growth and change microbial community structure.

Satellite image of a dust cloud from the Sahara Desert moving across the Atlantic Ocean

Satellite image of a dust cloud from the Sahara Desert moving across the Atlantic Ocean. Photo Credit: Photo provided by the SeaWiFS Project, National Aeronautics and Space Administration/Goddard Space Flight Center and ORBIMAGE. Image taken on August 8, 2001.

Saharan desert dust transported by easterly trade winds across the Atlantic Ocean provides pulses of nutrients, including iron, to ocean surface waters, yet the biological response to these events is not fully known, especially in the microbial community. Vibrio is a ubiquitous genus of marine bacteria that constitute a small fraction of the microbial community and are important in biogeochemical cycling of nutrients and trace metals. This genus also includes many well-known pathogens of marine organisms and humans, including the causative agent of the severe diarrheal disease cholera, shellfish-associated gastroenteritis, and seawater-associated wound infections; however, the research reported here did not assess the health effects or exposures to pathogens.

Scientists used a unique combination of simulated dust events in a laboratory setting and field sampling during a Sahara dust event in the Florida Keys to understand the effects of the dust on Vibrio bloom growth and changes in microbial community structure. The scientists determined that Saharan dust nutrients can promote rapid growth of the relatively rare Vibrio's and indicate that Vibrio species are "first responders" to dust-associated iron. This work indicates that marine bacteria play an important role in biogeochemical cycles related to periodic input of iron from Saharan dust-deposition and emphasizes that the periodic iron pulses rapidly increase the growth of marine bacteria, some of which are known to cause disease in humans and marine organisms.

The study was supported by the National Oceanic and Atmospheric Administration Oceans and Human Health Initiative S0867882; National Science Foundation Grants EF-1015342 and OCE- 1357423 and OCE-1357140, the United States Geological Survey's Toxic Substances Hydrology Program, and the Association of Marine Laboratories of the Caribbean.

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This article was featured in the USGS GeoHealth Newsletter, Vol. 13, No. 1, 2016