Dust clouds from the Sahara reach the Caribbean—and fertilize waters there when they arrive. Christopher Intagliata reports.
Residents of the southern U.S. might be familiar with this dusty summer phenomenon:
[TV Weather montage: "We are breathing dust that at one point originated over Africa… Dust particles are carried 15,000 feet into the atmosphere… Another dust cloud from Africa's Sahara Desert has made it all the way to Houston."]
The dust clouds surf on trade winds towards the Caribbean. And since the dust is rich in minerals, like iron, it's like an airborne delivery of fertilizer to marine life there.
"So when you get this pulse of iron that comes, it's a micronutrient, a trace metal that's needed by all of life that's all of a sudden available, at least for a short amount of time." Erin Lipp, a microbiologist at the University of Georgia. She and her team studied the phenomenon, sampling waters in Barbados and the Florida Keys. And they found that these fertilizer dumps seem to encourage bacterial blooms. Including Vibrio species, some of which can cause cholera or food poisoning.
"Vibrio and probably other bacteria that are really capable of responding to this feast that's provided to them, they just use it quite rapidly. So within that first 24 hours you see a very big population spike of these bacteria." A spike of five to 30 times their usual numbers. The finding is in the Proceedings of the National Academy of Sciences. [Jason R. Westrich et al., Saharan dust nutrients promote Vibrio bloom formation in marine surface waters]
If all this makes you want to skip the oysters after a sandstorm, "I would say that is a personal decision. But summer in general is the riskiest time to eat oysters." For now, she says, there's really no evidence to link Saharan dust to your risk of a bum oyster. So keep calm, and slurp on.
[The above text is a transcript of this podcast.]