[Coral-List] Lionfish and African Dust

Eugene Shinn eugeneshinn at mail.usf.edu
Wed Feb 5 15:51:18 EST 2014

After reading remarks by Doug Fenner, Matt Johnson, and Samuel Purkis 
regarding my short note relative to lionfish and /Diadema,/ it occurred 
to me that readers might have missed my point. It has been 14 years 
since we hypothesized that the 1983 Caribbean-wide near die-off of 
/Diadema/ and acroporid corals, and initiation of sea-fan disease, were 
likely caused by something carried in African dust *(Shinn et al., 2000, 
African Dust May be Cause of Coral Death. Geophysical Research Letters, 
v. 27, no 19, p. 3029-3032).* The smoking gun, /Aspergillus sydowii/ (a 
soil fungus), shown by Smith et al. (1996) using Koch's postulate, was 
the cause of the sea-fan disease. That African dust had negative 
environmental effects was regarded as an outrageous idea. However, 
abundant research has been conducted over the past 14 years that shows 
the good as well as deleterious effects of African dust on the environment.

African dust passing over the Cape Verde Islands is now widely 
recognized to hinder hurricane formation (some meteorologists still call 
it dry air). Iron in dust has been proposed to stimulate red tides, and 
iron is now recognized by chemical oceanographers (as originally 
proposed by John Martin) to stimulate primary productivity in the open 
ocean. Ligands in seawater are recognized for their ability to convert 
insoluble iron to bioavailable iron. That such dust clouds carried by 
trade winds often blanket the entire Caribbean has been repeatedly 
demonstrated in NOAA and NASA satellite images. The year 1983, a major 
El Niño year, correlated with coral bleaching in the eastern Pacific off 
Central America. Interestingly, major bleaching in the Caribbean and 
Florida did not occur until 1987. Besides being an El Niño year, 1983 
was the peak year of African dust flux to the Caribbean as measured at 
the Barbados monitoring station in operation by Joe Prospero since 1965. 
Dust flux at his station began rising in 1980 and continued to rise each 
year, culminating in the peak year 1983. Levels fell a little in 1984 
and 1985 (dropped to the 1981 level in 1986) but rose again in 1987 
before dropping back to 1979 levels. These were all significant years 
for coral distress, and diseases were reported well before 1983. In 
fact, black-band disease in brain coal was reported in Bermuda in 1973, 
which was also an earlier peak year for dust flux at Barbados. 
Correlation is not proof of causation of course, but correlation is 
certainly a stimulus for further research. In the case of African dust, 
no systematic experiments (controlled bioassays) other than the work on 
sea-fan disease have been conducted to test the hypothesis. Likewise, 
there have been no systematic controlled bioassays conducted on the 
effects of sewage pollution. The supposed association of sewage effects 
has also been one of correlation. Fortunately, some controlled 
experiments are now being conducted on the effects of sunscreen 
ingredients and pesticides on corals. One should wonder why such obvious 
experiments were not conducted years ago considering the seriousness of 
coral demise.

However, we now know more about the composition of African dust which, 
although dominated by silica, also includes P, Fe, Hg, Au, Al, Be-7, 
Pb-210, and in fact, most all of Earth's elements. Be-7 is a radiogenic 
gamma-ray emitter with a short half-life of only 53 days. It is produced 
high in the stratosphere by cosmic-ray spallation of nitrogen atoms and 
is continually raining to Earth at low levels but somehow becomes 
concentrated in dust clouds that reach the Caribbean. The levels of Be-7 
in the red sediment that accumulates in rainwater cisterns on Caribbean 
islands is many orders of magnitude greater than that ordinarily found 
in lawn grass. People in the Windward Islands and elsewhere in the 
Caribbean ordinarily breathe the dust during periodic dust-flux events 
whose densities often cause closure of airports on Caribbean islands. 
Residents there are well aware of its effects on respiratory systems. 
African dust also carries modern pesticides (some, such as DDT, still 
used in the Sahel region of Africa, are known immunosuppressants). The 
dust also transports many viable microorganisms.

USGS microbiologists have identified a profuse and diverse microbial 
community in airborne African dust; many microbes identified to the 
species level (bacteria and fungi) are known pathogens for plants and 
humans. The impact or influence of viruses associated with these 
globally dispersed dust storms is just beginning to be explored. Given 
that we can only culture approximately 1% of bacteria in any given 
sample type, the true extent and influence of these microbes that fall 
out of the atmosphere in downwind environments has only been touched upon.

So how does lionfish distribution support the dust hypothesis? 
Regardless of where the infestation began (probably in multiple 
locations), it took several years for the lionfish to be observed in the 
Windward Islands. Does anyone know exactly when the fish arrived there? 
I do not. For them to reach those islands, they would have to have moved 
against strong prevailing east-to-west currents. Alternatively, 
migration would require a circuitous route. After establishment in the 
Bahamas (where they were abundant before they were observed in the 
Florida Keys), they would then have to have worked their way 
southeastward to the northern Windward Islands and slowly emigrate 
southward along the island chain. From what I have read, it remains 
unclear whether they have bridged the current-swept gaps to reach the 
southernmost Windward Islands. At any rate, they apparently did not 
reach the Windward Islands as quickly as the /Diadema/ disease.

Now consider the /Diadema/ die-off events as reported in a comprehensive 
paper *(Lessios et al., 1984, Spread of /Diadema/ mass mortalities 
through the Caribbean. Science, v. 226, p. 335-337)*.According to those 
authors, mortalities began in the vicinity of the Panama Canal in the 
southwestern part of the Caribbean (the disease agent was initially 
thought to have come from a ship's bilge water) and within one year 
spread over the entire Caribbean including the Windward Islands. To 
accomplish this, the unidentified infecting agent, unlike swimming fish 
or fish larvae, had to have traveled against the strong prevailing 
east-to-west current that passes through the Windward Islands chain. 
Spread of the disease also reached remote Bahamian islands such as San 
Salvador and Rum Cay within one year. I do not know how long it took 
lionfish to reach San Salvador, but I suspect it was more than a year. 
Surely someone on that island likely knows when the fish first arrived.

These were the kinds of observations that initially led us to 
hypothesize that the infecting agent, whether elemental, chemical, or 
biological, had settled throughout the southern Caribbean from African 
dust clouds. The level of dust flux had been rising for several years 
before peaking in 1983. Dust levels remained high and did not subside to 
levels recorded between 1965 through 1968. Various coral diseases have 
not subsided since 1983, and although /Diadema/ exists in pockets 
throughout the Caribbean, pre-1983 levels have not been reported. They 
are extremely rare in the Florida Keys. One should remember that once 
material in the dust lands in the water, currents would then carry the 
agent northward in the manner that they transport Caribbean-derived 
lobster larvae that mature in the Florida Keys.

For reasons discussed, the relatively delayed arrival of lionfish in the 
Windward Islands versus the rapid Caribbean-wide dispersal of the 
/Diadema/ disease lends support to our original hypothesis that whatever 
infected /Diadema/, acroporid corals, and sea fans had dropped out of 
the atmosphere. That the levels of dust flux had been increasing for 
several years likely caused local outbreaks of coral disease. Key 
observations of reefs in St. Croix support this supposition. 
Nevertheless, the peak of coral disease and the/Diadema/ die-off 
occurred in 1983. Donald Gerace, head of the Finger Lakes Laboratory at 
San Salvador, described to me how a well-known nearshore /Acropora/ 
/cervicornis /reef had begun to die in a short period of time (less than 
2 months) during the summer of 1983. Those corals were entirely dead 
when I swam over the reefs with Phil Dustan a few months later. In 
addition, most all /A/. /palmata /around the island was also dead but 
still standing. Some time later, I observed similar dead acroporids 
around nearby Rum Cay, where locals told the same story we heard at San 
Salvador. San Salvador and Rum Cay are both surrounded by deep-Atlantic 
water and are isolated eastward of the other Bahamian islands. In 
Florida, acroporids showed signs of stress in the late 1970s as revealed 
in serial photographs that date back to 1960. These photographs clearly 
show that the main period of sudden and synchronous demise at the photo 
sites occurred in 1983. At San Salvador, acroporid death was sudden.

The red soil on San Salvador (called pineapple loam) is derived from 
African dust, and pottery there that pre-dates the arrival of Columbus 
was made from clay that had been fired. The only source of clay minerals 
in the Bahamas is African dust, the influx of which is not new. What is 
new is what the dust contains today.

In conclusion, the apparent delayed arrival of lionfish to the Windward 
Islands versus the swift and synchronous outbreak of /Diadema/ disease 
throughout the Caribbean is considered supportive of the African dust 

The recent identification of /Serratia marcescens/ in Florida Keys coral 
is a good step toward solving an evolving mystery. However, evidence 
that human fecal bacteria, and other elements in sewage, caused 
acroporid death simultaneously throughout the entire Caribbean, 
especially at sparsely populated isolated locales such as San Salvador 
seems a stretch.



No Rocks, No Water, No Ecosystem (EAS)
------------------------------------ -----------------------------------
E. A. Shinn, Courtesy Professor
University of South Florida
College of Marine Science Room 221A
140 Seventh Avenue South
St. Petersburg, FL 33701
<eugeneshinn at mail.usf.edu>
Tel 727 553-1158
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