Sept 15 final version

James M. Cervino cnidaria at
Mon Sep 15 22:40:43 EDT 1997

TO:   Readers of Bruckner comments on RWD and parrotfish posted on Coral List

FROM:  T. Goreau, J. Cervino, K. DeMeyer, I. Nagelkerken, R. Hayes, G.
Smith, M. Goreau

A. Bruckner has posted on the Web a claim that the condition
called Rapid Wasting Disease may actually be due to Parrotfish bites.

        Unfortunately Bruckner is criticizing data and interpretations
which have not yet been published, and therefore readers are unable to
assess the original information. We believe that his claim is in total
error, and present below some of the reasons why we think he is mistaken.

        Rapid Wasting Disease (RWD) spreads several inches a day on coral
heads in the field monitored every 24 hours, and also at a similar rate on
coral heads in aquaria and buckets which contain no parrotfish (Cervino
data). The parrotfish hypothesis was evaluated and rejected in a paper
containing photographs, transect data, distribution data, histology, and
microbiology. Because this is now under review at a leading scientific
journal, we are unable to post that manuscript with all the data at this
time, but the latest data will be available shortlyon the GCRA web site.

Microscopic examination of affected tissue edges show epidermal
inflamation and gastrodermal disruption which are consistent with a
spreading necrosis and not with physical bite excavations. We are extremely
familiar with parrotfish bite marks through detailed examination and
photography. Parrotfish bites form characteristic and unmistakeable grooves
and abrasion scars, and the affected skeleton lacks the crumbly,
dissolving, etched appearance characteristic of RWD. The
early stages of RWD are absolutely distinctive from parrotfish bites, as
the tissue pales and thins while the underlying skeleton surface any
physical damage.

When the tissue disappears the excavation can be as small as a single
polyp, an act of subtlety we have never seen parrotfishto perform. RWD
lesions in Bonaire were not seen before December 1996, andwere absent at
these sites until November 1996, according to regular long term monitoring
dives by the staff of the Bonaire Marine Park. The major RWD and Yellow
Band (YB) monitoring site in Bonaire has been the location of a large scale
study of parrotfish abundances, territories, and behaviour for many years
by researchers from the University of Groningen,who have documented in
detail all parrotfish behaviour patterns. Despite this close observation
the RWD lesions were not seen before December 1996.

 Parrotfish have been around all along, but the RWD type lesions are new.
Parrotfish bites were not a major cause of coral mortality in the past, and
parrotfish have declined greatly in most Caribbean reefs, especially the
terminal males responsible for territorial markings on coral. RWD has
increased hundreds of times in the last year. Once too rare to be noticed,
it is now too abundant to be missed. RWD is so stark
in appearance that there is no possibility that it was present but
unnoticed in the past:  we have large numbers of reef photographs from the
1940s, 1950s, and 1960s which demonstrate this. If parrotfish cause or
transmit "RWD" it should have been common and widespread in the past and
declined in overfished reefs. Instead the opposite has happened. RWD was
not seen at all in Portobelo, Panama in July 1997 despite abundant
large parrotfish (which are not eaten locally), and conversely RWD was very
common in St. John in September 1997 despite a near absence of parrotfish.
This is the opposite of what Bruckner would predict. Observations from
other locations show no particular relationship betweenRWD lesions and
parrotfish abundance.

Large numbers of very old Colpophyllia colonies which are beautifully
rounded had no signs of growth abnormalities or missing chunks until
recently, yet have been rapidly killed by RWD this year. Have remaining
parrotfish increased coral consumption hundreds or thousands of times and
suddenly wiped out ancient corals which had never been affected before,
based on their morphology? Parrotfish bite any
available algal turf and calcareous algae more frequently than corals by
orders of magnitude. Parrotfish which bite corals normally specialize on
Porites, whose wounds heal over completely with no signs of infection. In
the past when parrotfish did bite Montastrea the dead areas were surrounded
by healthy tissue which overgrew the edges of the wounds without signs of
necrosis.  If parrotfish bites cause secondary diseases to develop why did
this not happen before? Parrotfish rarely if ever bite Colpophyllia natans
tissue (although they do bite algae growing on dead Colpophyllia
skeletons). We observe parrotfish to frequently graze readily on the algal
turf which overgrows portions of colonies previously killed by RWD and
other diseases, but they confine themselves to the algae and do not attack
the coral tissue. Close observation of the bite marks is needed to see
where they actually bite.  We suspect that Bruckner confused grazing on
algae turf on dead portions of corals with attacks on the live coral. We
have video documentation of this behaviour, and the bite scars were always
found to be on algal turf and not on the coral tissue.

Bruckner claims that only one coral out of six has YB and one out of a
thousand have RWD. We are baffled at Bruckner's reports of very low disease
abundances reported for Bonaire in June. We have tracked around 16 sites in
Bonaire and Curacao between February to July and find verymuch higher
numbers of incidence. We have hours of video transects from many sites in
which the incidence of both diseases are between 30 and 80% or more. These
abundances are corroborated by transect data taken by Cervino in Bonaire
and St. John, by Nagelkerken at sites in Curacao, by obervations by the
Bonaire Marine Park, and in numerous transects around Bonaire and Curacao
in a monitoring project run by Project Reefkeeper. We suspect that Bruckner
has failed to properly identify RWD and YB.  We observe that RWD is
underestimated by many because it is commonly mistaken for bleaching, other
diseases, physical damage, and unknown causes of mortality. We note below
some differences between RWD and YB,
and why these have apparently been underestimated. RWD attacks the skeleton
as well as tissue but YB attacks only tissue. RWD usually hits the tops of
the coral heads, and YB usually hits the sides. Often after RWD has killed
the tops, YB finishes off the sides.  One must look very close up at the
surface of the recently dead coral skeleton to
distinguish these causes of mortality. After a suitable period after death
from either cause, the coral is overgrown by calcareous encrusting red
algae if nutrients are low, and by algal turf or cyanobacteria if nutrients
are high, making identification of the original cause of death much harder.

Transect data, diagnostic photographs, videos, and maps of all Caribbean
reef diseases plus global data, will be posted on the Global Coral Reef
Alliance web site within weeks. We will post the address as soon as it is
up. We invite Bruckner to submit his photographs and videos to this site
once it is running, so that he and other viewers can compare them with the
data and images from a large network of observations from around the
Caribbean. We regret that he did not contact us or the Bonaire Marine Park
to discuss the observations, or look at the photographs before posting his
claims, as these could have been easily resolved had he checked with us.

James Cervino will be presenting this data in Woods Hole (tentative date
Mon. Oct 6th 97), along with his photographs and Tom Goreau's videos.
Photos of Parrot fish bite marks and photos of RWD in a 24 hour sequence
will be shown which indicate the drastic differences. Data and photographs
of the spread of the disease in the field, in aquaria, and in buckets will
be shown.

Please send comments to cnidaria at & goreau at

Thomas J. Goreau, Ph.D., President
Global Coral Reef Alliance                                 324 Bedford Road
A non-profit organization for protection           Chappaqua, New York 10514
and sustainable development of coral reefs       USA

e-mail:        goreau at
phone:          914-238-8788
fax:              914-238-8768

James M. Cervino
Marine Biologist
Global Coral Reef Alliance
124-19 9th ave, College Point NY 11356
Phone/Fax 718-539-8155

More information about the Coral-list-old mailing list