[Coral-List] Excess algal symbionts increase coral susceptibility to bleaching

Eugene Shinn eshinn at marine.usf.edu
Fri Nov 16 17:34:11 EST 2012

Andrew, This is very interesting information especially because 
you're findings relate the combined effects of temperature, oxygen, 
and nutrients to bleaching.  We certainly have all three, including 
anthropogenic nutrient sources, in Florida but I keep remembering the 
sudden die-off of Acroporids at San Salvador in 1983. That was a time 
when there were few anthropogenic sources on that sparsely populated 
island surrounded by deep oceanic water. John Martins original 
discovery that iron was necessary for algal growth has been re 
confirmed by many experiments since then. Because 1983 and 1984 were 
peak years for African dust flux to the Caribbean I continue to 
wonder if it contained sufficient iron (also phosphate) to provide 
this necessary micro nutrient? It is certainly the source of the red 
soil on that otherwise limestone island. Could the 5-6 percent iron 
contained in African dust be sufficient to cause overstimulation of 
both cyanobacteria and dynoflagelate zooxanthellae and thus cause 
their expulsion i.e. bleaching?
       Considering the co incidence of bleaching events with years of 
increased dust flux and warm quiescent summers makes one wonder. The 
year 1998 was especially warm and dust flux as measured at Barbados 
by Joe Prospero was almost as high as it was in 1983 and 1984. With 
such obvious correlations one would think that some curious coral 
biologist would have performed dosing experiments to validate or 
discard the dust hypothesis. Gene  PS: here is a great image of the 
dust belt provided by Douglas Fenner. 


No Rocks, No Water, No Ecosystem (EAS)
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E. A. Shinn, Courtesy Professor
University of South Florida
College of Marine Science Room 221A
140 Seventh Avenue South
St. Petersburg, FL 33701
<eshinn at marine.usf.edu>
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