A new study conducted in collaboration with a group of scientists from the University of Georgia suggests the Vibrio bacteria, commonly found in the world's oceans, and well-known for its capabilities of causing serious illness to both human population and marine organisms, are highly responsive to an influx of iron-rich Saharan dust. This influx causes large, widespread blooms of the potentially harmful bacteria across the surface waters.
Vibrio bacteria are capable of swift reproduction and are highly receptive to newly available resources, newest research shows.
"Part of what makes these normal marine bacteria also potentially pathogenic is their ability to grow quickly when conditions are favorable, whether in a host, or, in the environment," said Erin Lipp, a professor of environmental health science in the UGA College of Public Health, and a co-author of the study.
"While we are interested in how the population dynamics of Vibrio might cause disease, for this study we wanted to use Vibrio's opportunistic behavior as a model for how bacteria could exploit the availability of new nutrients and, in particular, iron delivered in dust."
Saharan dust heading west toward South America and the Gulf of Mexico on June 25, 2014. Image credit: NASA/Aqua MODIS/Suomi NPP/Norman Kuring/NASA’s Ocean Color web/Adam Voiland
Iron, contained in dust particles is certainly capable of causing test cultures of Vibrio bacteria to grow, according to laboratory-based results. The team has traveled to the Florida Keys and Barbados to confirm this finding in natural conditions by measuring the Vibrio growth during naturally occurring Saharan dust events.
The experts had observed the dissolved iron increases in ocean surface waters when the dust arrived, and the growth of Vibrio bacteria from a background level of only 1% to almost 20% of the total microbial community in a 24-hour exposure interval.
Saharan dust is a major source of iron for the oceans across the globe. Iron is extremely important to biological production, and seeding ocean regions have been investigated as a means of stimulating the phytoplankton growth. Generally, phytoplankton is considered highly important for the Earth's climate, as they are capable of absorbing carbon dioxide, thus potentially mitigating effects of climate changes. This outlook is mainly based on an assumption that the phytoplankton is the first responder to nutrients influx.
This portrait of global aerosols was produced by a Goddard Earth Observing System Model, Version 5 simulation at a 10-kilometer resolution. Dust (red) is lifted from the surface, sea salt (blue) swirls inside cyclones, smoke (green) rises from fires, and sulfate particles (white) stream from volcanoes and fossil fuel emissions. High-resolution global atmospheric modeling run on the Discover supercomputer at the NASA Center for Climate Simulation at Goddard Space Flight Center, Greenbelt, Maryland, provides a unique tool to study the role of weather in Earth's climate system. Credit: William Putman, NASA/Goddard
However, the new research shows the Vibrio's responsive abilities potentially surpass the phytoplankton's, which suggest the Vibrio bacteria could be a highly important factor in the biogeochemical iron cycle, and critical to numerous planetary processes.
"Previous studies have primarily focused on the biological response of phytoplankton and algae to Saharan dust disposition, so the role that bacteria play has largely been overlooked," said Jason Westrich, a postdoctoral research associate in the College of Public Health, the lead author of the study.
Vibrio bacteria illness cases are increasing at a rapid rate, higher than numerous other bacterial pathogens in the US. This could, partially, be related to Vibrio bacteria populations in coastal waters spreading as the sea surface temperatures rise. Also, an increased desertification in the Sahara could produce more dust events inducing potentially harmful Vibrio blooms.
"Knowing the connection between Saharan dust and Vibrio population blooms is significant from the perspective that we are able to track these dust events using satellites in real time. This allows some predictive power to understand when there is an increased risk for Vibrio infection in humans and other marine organisms," Westrich said.
- "Saharan dust nutrients promote Vibrio bloom formation in marine surface waters" – Jason R. Westricha, Alina M. Eblingc, William M. Landingc, Jessica L. Joynera, Keri M. Kempa, Dale W. Griffind, and Erin K. Lippa – Proceedings of the National Academy of Sciences (2016) – doi:10.1073/pnas.1518080113
Featured image credit: William Putman, NASA/Goddard
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