Desert storms could be kiss of death for coral

A dust storm swirls off the northwestern coast of Africa on February 26

By Environmental News Network staff

March 8, 2000
Web posted at: 11:54 a.m. EST (1654 GMT)

Are huge dust storms from Africa's deserts killing the coral in the Caribbean Sea?

"I've been watching this for about 40 years," said U.S. Geological Survey scientist Gene Shinn. "The years with high dust were the same years most of the coral were damaged."

"No one has gotten into looking at the potential health effects or what dust does to the environment," said Shinn, a self-proclaimed "dust nut" who's hoping to raise awareness and funds for his cause.

Coral reefs throughout the Caribbean have been plagued by algal infestation, disease and attrition since the 1970s. Beginning about the same time, scientists noticed that desertification in North Africa was moving sand and other particulate across the Atlantic Ocean.

Changes in climate send strong winds loaded with African dust, soil, and organisms westward over the Atlantic. Earlier this week, NASA's SeaWiFS satellite, which takes pictures of Earth from space, captured one of the largest dust storms ever recorded by the spacecraft.

The dust ball is full of bacteria, viruses and fungi that are deadly to coral, according to Dick Barber of Duke University in North Carolina. It is also rich in iron, which fertilizes reef-choking algae, he said.

This large, nearly dead star coral, photographed in 1998 at Grecian Rocks, Florida, was ravaged by "black band" disease

Shinn believes algal infestation, coral bleaching and coral killers such as "white band" and "black band" diseases are connected to the nearly two billion tons of dust that each year blow from North Africa to the Caribbean.

"After we looked around and noticed coral was dying all over the Caribbean, not just in Florida where we have sewage and other problems, I found some literature on the Amazon rain forest," Shinn said. "In the late '80s and early '90s, scientists determined that the African dust supplies most of the essential nutrients for the rain forest."

The best evidence of Shinn's theory is Aspergillis, a fungus normally found in soil, that has devastated a particular species of coral. Since 1983, when Aspergillis first appeared, it has killed more than 90 percent of the Caribbean's sea fans. The same year — an exceptionally dusty one — Diadema sea urchins drastically declined, which, in turn, triggered algal infestations in the reefs.

Dust from Africa carries millions of spores similar to Aspergillis. "It's a veritable soup of stuff," he said.

Millions of dollars have been spent researching sedimentation, sewage, pollution, ship groundings, temperature and other coral enemies, Shinn noted. But none of these potential killers explain why coral disease and algal infestation occur simultaneously throughout the Caribbean, especially in remote areas with little human activity.

One theory blamed deforestation runoff on coral demise. Shinn blames dust balls. "We looked at the dust," said Shinn. "That would explain how it could be all around the Caribbean, even in areas with no forests around."

Understanding the relationship between African dust and the demise of coral reefs could redirect research efforts.

Shinn and colleagues are analyzing dust trapped in coral skeletons. The data will be compared with climate records and dust levels from key Caribbean collection sites.

New coral cores will be collected from Caribbean reefs in the Virgin Islands. Older coral cores, stored at a St. Petersburg, Florida, laboratory, will be analyzed for any correlation with the new cores.

Other microbiologists will examine fresh dust collected in the Virgin Islands for fungal and bacterial spores.

"All I'm trying to do is make people aware because most don't even think of this," said Shinn. "And it does affect people's health, no doubt about it."

Copyright 2000, Environmental News Network, All Rights Reserved

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NASA's SeaWifs project
USGS site on coral mortality and African dust

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