coral reef diversity

Marjorie Reaka mr9 at
Thu Jun 21 13:35:06 EDT 2001

	The appropriate citation for my work on estimates 
of the number of DESCRIBED and POTENTIAL (described plus 
undescribed) species in coral reef ecosystems, along with a 
discussion of the methods and numerical basis of the 
calculations, and the assumptions and complexities involved 
in such a calculation, is Reaka-Kudla, M. L. 1997. The 
global biodiversity of coral reefs: a comparison with 
rainforests. In: M. L. Reaka-Kudla, D. L. Wilson, and E. O. 
Wilson, eds., Biodiversity II: Understanding and Protecting 
Our Natural Resources.  Joseph Henry/National Academy 
Press, Washington DC, pp. 83-108.  I concluded that there 
are about 93,000 described species of all taxa (including 
microoganisms) and about 68,000 described species of 
macrobiota.  This is about 5% of the described global 
	If one tries to estimate how many total species 
there MIGHT be on global world reefs, one can use a variety 
of data and methods, including the estimates of the % of 
species among all organismal groups that have already been 
described (e.g., Systematic Agenda 2000 and other 
reports)--and thus how many remain to be described, and how 
many species coral reefs might have IF they possessed the 
same species/area as rainforests (and using bracketed 
numbers from published estimates of total numbers of 
species in rainforests).  I concluded (p. 102) that total 
coral reef diversity (known plus unknown species, including 
microorgansisms) might be about a million species (the 
calculation suggested 950,000).  However, the number could 
be higher, since microorganismal diversity is so poorly 
known, since even most macroscopic species on coral reefs 
are cryptic and difficult to collect, since many of these 
species of small body size have small geographic ranges, 
and since the tropics and marine environments (especially 
in remote regions) receive less study than terrestrial and 
higher latitude environments.  It has been a source of 
considerable consternation to me that this work, and the 
careful bracketing of assumptions and numbers underlying 
it, has been badly misquoted by some individuals and the  
World Resources Institute who apparently did not read the 
paper and treated it as if it was just a wild guess.  

  On Mon, 18 Jun 2001 09:32:22 
-0500 Juliet Martinez <Juliet.Martinez at> wrote:

> Dear Coral List,
> I am a researcher/fact checker at World Book 
Encyclopedia, currently checking the article entitled 
"coral reef" that will appear in the 2002 print edition. I 
have a few questions on statements that appear in the most 
recent draft, but which I am having difficulty verifying in 
current literature. Austin Bowden-Kerby answered some of my 
questions and suggested I address the list with the others. 
> > 1. Does everyone agree that the Great Barrier Reef is 
the world's largest reef system by area? Does anyone know 
the actual length (I know it's about 2000 km, but would 
prefer a more exact measurement)  and area for the GBR? One 
source I have says that the largest reef system is a 
fringing reef system in the Red Sea, at 4000 km long.  In 
search of these answers I have emailed the Australian 
Geological Survey and Reefbase, but gotten no response. > 
> 2. Do coral reefs occur in the subtropics? The article 
contributor says they do, but since most of my sources say 
that coral reefs occur in the tropics only, I could use 
some examples of sub-tropical coral reefs. I also realize 
that non-hermatypic corals grow in much colder water, 
deeper in the ocean, and outside of the tropics, but do 
they occur as far north as the Arctic Circle? > 
> 3. To what family do the sea grasses belong? The lily 
family? > 
> 4. What is the best authoritative estimate of the total 
species richness of coral ecosystems? I've found the 
following: "thousands" (Castro and Huber. Marine Biology. 
1992), "tens of thousands" (NOAA's coral page), and "one to 
nine million" (Marjorie Reaka-Kudla, cited in Science, and 
by the World Resource Institute). How would most of the 
coral reef scientists ballpark it? I'm looking for the 
current scientific consensus on it. Also: What is the 
ballpark number of reef-building coral species? > 
> 5. How old are the oldest known coral reefs? > 
> 6. Some sources list coral reefs as an important carbon 
sink. Others say that the coral reefs only account for 
about 2% of global carbon storage, and contend that as 
such, they are not a significant carbon sink. Again, I'm 
looking for the scientific consensus on this, if one 
exists. > 
> I appreciate the assistance of any and all who can take 
the time to reply. Please bear in mind that the goal of the 
article is to present an informative article that reflects 
current scientific consensus. Also, please include your 
position and credentials so that I can cite your assistance 
in my list of sources. > 
> Thank you, > 
> Juliet Martinez > 
> Research Department > World Book Encyclopedia
> 233 N. Michigan, Suite 2000 > Chicago, IL 60601
> P: 312-819-6554 > F: 312-729-5612
> E: jmartine at > 
> ~~~~~~~ > For directions on subscribing and unsubscribing 
to coral-list or the > digests, please visit, click on Popular on the > menu bar, 
then click on Coral-List Listserver. > 

Dr. Marjorie L. Reaka-Kudla Professor
Department of Biology
The University of Maryland
College Park, Maryland 20742
Telephone 301-405-6944
Fax 301-314-9358
mr9 at

For directions on subscribing and unsubscribing to coral-list or the
digests, please visit, click on Popular on the
menu bar, then click on Coral-List Listserver.

More information about the Coral-list-old mailing list