[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.
<http://www.nasa.gov/multimedia/imagegallery/image_feature_2393.html>
--
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>
Tel 727 553-1158----------------------------------
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