CORALS: Climate change isn’t the only threat facing corals—African dust carrying fungal spores are causing deadly lesions and infections, which are killing corals

IMAGE above is a satellite image showing dust settling over the Caribbean and Amazon regions of the New World. This dust carries deadly fungal spores, which are causing deadly lesions (right) in corals.

Dust from Africa blows over to seed the Amazon rainforest and the Caribbean Sea. However, this dust may be causing coral deaths. The reason for these coral deaths is explained by the dust hypothesis. Some scientists link the increase in African dust to desertification. Desertification is the result of drought, overgrazing, and poor soil management, and it increases the volume of African dust. So how does African dust result in the death of corals living far away in the Caribbean Sea? The answer is in the dust’s makeup or contents. Fungal spores from the aspergillus fungus are found in the dust, and this fungus causes coral aspergillosis, which is a “lesion producing fungal infection” that attacks coral tissue and results in characteristic lesions all over the corals. Corals aren’t the only living things being affected by the African dust, since asthma rates are also increasing in the Caribbean region as well. From CNN International:

The drought in Africa may be partly to blame for a decline in the coral in the Caribbean Sea, according to a team of researchers who found coral-damaging fungi in dust blown across the ocean.

“Coincidental with the decline of Caribbean coral reefs over the past 25 years, there U.S. Geological Survey Center for Coastal Geology.

With the long-term drought in Africa, combined with overgrazing in many areas, the amount of dust carried across the oceans has been increasing and is now estimated at several hundred million tons annually.

And the threat may not be limited to corals, Shinn said in a telephone interview.

“We have moved into the realm of public health because the dust is bringing lots of bacteria,” commented Shinn, who said his research team has now added a microbiologist to study what types of microorganisms might be carried on the dust.

In 1989 some one-inch grasshoppers from Africa made it to the windward islands in a dust storm. “If they can make it, think of all the other things that can make it,” he said.

“Dust often reduces visibility in the Virgin Islands, sometimes causes temporary closing of airports, and is easily verified as African in origin by tracking dust clouds across the Atlantic with … satellite data,” the scientists reported.

“Our hypothesis is that some of the decline of the reefs in this region is linked to the increase in dust transport,” the team said in a paper scheduled to appear in the Oct. 1 issue of Geophysical Research Letters.

Aridity and desertification in northern Africa began increasing in the mid-1960s, worsened in the 1970s and 1980s and then began to lessen in the 1990s.

Major episodes of Caribbean coral mortality occurred in 1983 and 1987, which were also the two years of the greatest dust movement, Shinn pointed out. He said iron and other minerals in the dust affected the water conditions.

In the mid-1990s an epidemic struck sea fans in the Caribbean and the cause was found to be the soil fungus Aspergillus, the team noted.

At the time the presence of Aspergillus was attributed to increased runoff caused by deforestation on Caribbean islands, but outbreaks also occurred around isolated islands that had no forests.

Shinn’s team tested dust samples collected from the air arriving at the Virgin Islands and discovered several species of fungi, including Aspergillus.

“African dust is an efficient substrate for delivering Aspergillus spores; spores are absent when the air is clear,” they concluded.