RAPID WASTING DISEASE

[Dr. Ernesto Weil]

Dear  Mr.  Cervino and coral disease colleagues,

We would like to share some important information with you all about the
recently described "Rapid Wasting Disease".  We are using Dr. Weil's
e-mail at this point because our e-mail system is down. Any comments could
be addressed to the e-mail address at the bottom or through Dr. Weil's
address if there are problems.

We have been following the coral-list information concerning the recent
increase in coral disease and the discovery of a new disease, termed rapid
wasting disease.  We have monitored reefs in Jamaica and Puerto Rico over
the last 6 years; we routinely spend 5 days per week in the field, which
provides an excellent opportunity to follow the spread and impact of coral
diseases. While our research indicates that disease is an important
component contributing to a decline of live coral, we have occasionally
identified corals with lesions (especially C. natans and M. annularis)
devoid of tissue and skeletal material, and have attributed this damage to
parrotfish.
In June 1997 we ran a series of transects on reefs of Bonaire and Curaçao
to examine the apparent health of the star coral complex (Montastraea
spp.), the major reef builder on these reefs.  Our data from 6 reefs in
Curaçao indicate that star corals were infected primarily by yellow-band
disease (YBD), with a low proportion of corals showing signs of other
diseases as well as "rapid wasting disease" (RWD).  While YBD was observed
on up to 1 in 6 corals, and was found at all depths,  RWD was rare (<0.1%),
patchy in occurrence, and absent from deeper reef areas (>25 m).  Surveys
in Bonaire indicate that YBD is also the most severe affliction, although a
high proportion of corals above 20 m exhibited signs characteristic for
RWD.  The most severe damage from RWD was observed on (but not confined to)
reefs along the northwestern half of the island.
We monitored colonies of M. annularis in Bonaire with recent tissue and
skeletal destruction for up to 70 min each.  We observed 2/3 of the
colonies with fresh lesions being attacked by stoplight parrotfish
(Sparisoma viride) at least once, and usually repeatedly.  During these
periods, 1-3 terminal phase male and several initial phase adult S. viride
removed live coral tissue and skeleton from a single coral head, returning
at 2-15 min intervals.  In two cases, fish removed the majority of the
tissue from one lobe, then began grazing on an adjacent lobe.  S. viride
also attacked C. natans; fish removed all tissue and skeletal material in a
band, moving methodically across the coral. 
Bruggemann et al. (1994) investigated the ecology of stoplight parrotfish
in detail on one of these reefs in Bonaire (Karpata), noting that these
fish maintain and defend permanent territories in 3.5-25 m depth1. While
Bruggemann et al. noted that most bites were taken on algal turf associated
with dead coral, 9.3% of the bites taken by TP males were from living
corals, primarily M. annularis, creating conspicuous white spots on the
colony.  Affected corals were located most frequently near territory
boundaries; they believe these "'white spot' bites
function in
consolidating the social interrelationships between individuals and groups"
1.   Parrotfish consumed most material bitten off, however "spilling of
material that was scraped off but not ingested was occasionally observed in
the field.  Sometimes the entire potential food mass was spit out, which
occurred mainly when bites were taken from live coral" 1.
Predation by stoplight parrotfish was the most serious cause of chronic
coral tissue loss to M. annularis in the U.S. Virgin Islands2.  Parrotfish
grazing on live coral was temporally variable; the most severe damage,
affecting over 10% of the surface area of individual genets, and 25% of the
monitored colonies, was observed during a one year period following
Hurricane Hugo2.  Frydl and Stearn  (1978) concluded that stoplight
parrotfish were the only species that caused significant bioerosion in
Barbados3.    They observed that a bite caused by the stoplight parrotfish
"leaves a well defined scar even when afflicted by a medium sized fish";
when feeding on rubble encrusted with algae and forams, fish "peel off the
encrusting layer, and remove part of the substrate beneath it" 3.
On reefs in Puerto Rico we have observed  C. natans and the species of
Montastraea with signs of  "rapid wasting disease" since 1995, although at
a much lower abundance;  this is most likely a result of intense fishing
pressure here.  Stoplight parrotfish is now predominant in the fish
markets, as other, more desirable species are becoming rare.  This is
further evidence for the extreme numbers of corals being denuded of tissue
and skeleton in Bonaire, where spear and trap fishing have been banned for
17 years.  Our observations of M. annularis in Bonaire indicates this
phenomenon has been occurring for years, as some colonies show sites of
previous damage (months to years) where the coral has begun to grow up
around the lesion.

We believe that parrotfish bites have been mistaken for this newly
described RWD and that fungus may be a secondary colonizing agent after the
 parrotfish produces the lesions. While the extent of damage caused by
stoplight parrotfish may vary temporally and spatially between reefs, our
data provide evidence that stoplight parrotfish can produce lesions on
colonies of star coral which demonstrate all the characteristics of  "rapid
wasting disease" . 

Even though rapid wasting disease may in fact be the result of something
other than a disease-causing pathogen, the importance of diseases in the
coral reef ecosystem can not be stressed enough.  Research is needed to
investigate diseases such as YBD, white plague type II,  and white pox,
which may have appeared in this decade, and are thought to have increased
in prevalence and severity over the last few years.  Regular monitoring of
the apparent health of reefs is necessary to understand the mechanics of
coral disease spread and to properly identify other destructive agents. 

1. Bruggemann, J.H., M.J.H. van Oppen and A.M. Breeman. 1994. Foraging by
the stoplight parrotfish Sparisoma viride. I. Food selection in different,
socially determined habitats. Mar. Ecol. Prog. Ser. 106:41-55.
2. Bythell, J.C., E.H. Gladfelter and M. Bythell. 1992. Ecological studies
of Buck Island Reef National Monument, St. Croix, U.S. Virgin Islands. Part
II. P 40-61. 
3.  Frydl, P. and C.W. Stearn. 1978. Rate of bioerosion by parrotfishes in
Barbados reef environments. J. sediment. Petrol. 48: 1149-1158.

Andrew and Robin Bruckner
Department of Marine Sciences
University of Puerto Rico
P.O. Box 908
Lajas, PR 00667
arbruckner at hotmail.com