[Coral-List] African Dust?

John McManus jmcmanus at rsmas.miami.edu
Tue Jul 26 17:53:21 EDT 2005

Robert Carpenter showed many years ago that the central Caribbean Sea was
highly iron-limited. Adding small amounts of iron enabled cyanobacteria
(blue-greens) to fix nitrogen and bloom in massive amounts. This may or may
not be the case for waters near shore, including most Caribbean reefs.
However, I would be surprised if the iron-rich Saharan dust did not cause at
least offshore blooms. 
	Basically, the offshore waters had excess phosphorous in
biologically accessible forms, but not enough useable nitrogen to support
much phytoplankton. Cyanobacteria require iron and molybdenum within the
complex molecule they use to "fix" nitrogen (get it into a form that can be
assimilated biologically). In lakes, either or both metals can limit
cyanobacteria. In seawater, molybdenum is not hard to get, but iron is often
limiting. If the blooms do occur over reefs, they may affect reef ecology --
not only because of the large amounts of cyanobacteria (and maybe oxygen
depletion as they die), but also because the nitrogen that has been fixed is
not available to the reef food web. 
	All this is in addition to the other potential impacts of the dust,
such as possibly the coral diseases discussed by Shinn, Grice, and others.
Of course, previous dust storms have been shown to lead to increases in
asthma and other non-reef problems.   


 *** Please note new phone numbers (361 now 421) ***
John W. McManus, PhD.
Professor, Marine Biology and Fisheries
Director, National Center for Caribbean Coral Reef Research (NCORE)
Rosenstiel School of Marine and Atmospheric Science
4600 Rickenbacker Causeway, Miami, FL, 33149
305-421-4814, 305-421-4820,       Fax: 305-421-4910
jmcmanus at rsmas.miami.edu
"If I cannot build it, I do not understand it." -- Richard P. Feynman, Nobel

-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of
kalai21 at earthlink.net
Sent: Tuesday, July 26, 2005 7:36 AM
To: Jesse Miller; coral-list at coral.aoml.noaa.gov
Subject: Re: [Coral-List] African Dust?

I would think that its biologically signficant, b/c of the minerals it will
be depositing into the ocean. The interesting part is to see where the bulk
of it lands. 

-----Original Message-----
From: Jesse Miller <jessem at olemiss.edu>
Sent: Jul 25, 2005 11:38 AM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] African Dust?

Hello Coral-Listers.

Does anyone have any thoughts about the cloud of dust approaching us from
the Sahara?  Is anyone worried about this in light of recent articles on the
subject? http://coastal.er.usgs.gov/african_dust/reference.html
Just wondering how the populace feels about this phenomenon as a whole.

Jesse Miller
Jesse Miller, Ph.D.
Post-Doctoral Fellow
National Institute of Undersea Science and Technology
University of Mississippi
443 Faser Hall
University, MS 38677
jessem at olemiss.edu
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