Please help with research questions

Jamie Oliver j.oliver at
Thu Jun 21 01:07:46 EDT 2001

Dear Juliet,

Thank you for your efforts to provide accurate information on coral
reefs in the World Book Encyclopaedia. Due to relocation of the ReefBase
office, I was not able to respond to your email from last Thursday. I'd
like to take this opportunity to  address questions 1-4 through the
coral list (see below), to allow for further feedback/comments from other
coral scientists. Hope this is of help.


Dr. Jamie Oliver
Project Leader
ICLARM-The World Fish Center

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.
The Great Barrier Reef Marine Park Authority  (, lists a
length of 2300 km and a total area of 347 800 km2 for the Great Barrier Reef
World Heritage Area. This includes deep waters, non-reef areas etc, but
excludes the area of the Torres Straits north of the tip of Cape York. About
6% of the listed area is estimated to be actual coral reefs, amounting to 20
868 km2. Whether this is the largest area for any reef system in the world,
depends on your definition of a Reef System. The 4000 km you mentioned for
the Red Sea, probably reflects the Red Sea coastline where coral reefs are
abundant but highly scattered. Even if you consider all Red Sea reefs to be
a single system in the same way that the GBR is considered a single system,
then the total area of reefs is probably less than the GBR (although the
length is greater). However if you consider the archipelagic fringing reefs
of Indonesia to be a single system then this would certainly amount to more
than the GBR.

If you define reef system to be a visually distinct aggregation of shallow
reefs then the GBR is clearly the largest in the world, with the Belize
Barrier Reef system coming in second.

UNEP-WCMC have recently completed a World Atlas of Coral Reefs which
contains the most accurate information on coral reef area per country
(  This atlas will be published
in a few months time.  Ultimately it is hoped that queries on reef area and
other UNEP-WCMC derived reef statistics will be possible via UNEP-WCMC and
ReefBase websites.


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?
Yes, coral reefs do occur in the subtropics where currents provide warm
tropical water, but they are best developed in the tropics.   A good example
is Bermuda (32.3 N), which is in the Gulf Stream. Other examples of
sub-tropical reefs can be found for Japan. The highest latitude reefs have
been reported for Iki Island, Japan (N 33'48"/E130'00"). In the southern
hemisphere, examples of high latitude reefs include Lord Howe Island (31.5
S) and the Houtman Abrolhos reefs (29 S) off eastern and Western Australia
respectively.  An excellent source for further information on coral
biogeography is: Veron, J.E.N. (1995). Corals in Space and Time. Australian
Institute of Marine Science. Cornell University Press, Ithaca, USA.


3. To what family do the sea grasses belong? The lily family?
Seagrasses are the sole marine representative of the Angiospermae. They
all belong to the order Helobiae, in two families: Potamogetonaceae and
Hydrocharitaceae. They are closely related to lillies (family
Lilliacea), but belong to different families. E.g. see:


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?

I would not like to hazard a guess regarding the total number of species on
coral reefs. However, there are 794 hermatypic Scleractinia (reefbuilding
which have been described. The authoritative publication on coral species
taxonomy is: Veron, J.E.N. (2000). Corals of the World. Australian
Institute of Marine Science, Townsville, Australia.

Jamie Oliver
Senior Scientist (Coral Reef Projects)
ICLARM - The World Fish Center
PO Box 500, Penang 10670

Phone: (604) 626 1606
Fax: (604) 626 5530

email:  J.Oliver at

Jamie Oliver
Senior Scientist (Coral Reef Projects)
ICLARM - The World Fish Center
PO Box 500, Penang 10670

Phone: (604) 626 1606
Fax: (604) 626 5530

email:  J.Oliver at

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