Part 2

[Eric Borneman]

Sorry for earlier multiple replies...

Finally:

For anyone interested in reading more real information about coral disease, I would highly suggest the following papers:

Richardon, L. L. 1998. Coral diseases: what is really known?" Trends in Ecology and
Evolution 13 (11): 438-443

Santavy, D. L., and E. C. Peters. 1997. Microbial pests: coral disease in the western
Atlantic. Proceedings of the 8th International Coral Reef Symposium, Panama. 1:
607-612.

Antonius, Arnfried. 1995. Pathologic syndromes on reef corals: a review. In: Coral Reefs
in the Past, Present and Future (Lathuiliere, Bernard and Jorn Geister, eds.). ISRS,
Proceedings of the Second European Regional Meeting, Luxembourg September 6-9, 1994: 161-169.

White Band Disease (WBD)

Both Antonius and Gladfelter first described this disease in 1977. White-band disease is common to many small-polyped and large-polyped corals. A progressive white band of skeleton occurs, resulting from tissue loss that advances at a rate of several millimeters per day across the coral colony (Antonius 1981, 1981, 1985, Peters 1997). WBD frequently begins at the shaded base of corals or in weakened areas of the skeleton. According to Antonius, White Band Disease often serves as a starting point for Black Band Disease (Antonius 1977-85). Peters (1997, personal communication 1998) has also indicated that WBD can begin in A. cervicornis at the mid-branch level, and her work indicates that the base tissue does not necessarily require shading. Although tissue may superficially appear normal at early stages, degenerative changes and partial necrosis may be present. It is slow acting, and is seldom reversible when it occurs in wild coral communities.

WBD has not yet been found to be contagious to other corals (Antonius 1981, 1981a, 1985). There is no unusual accumulation of organisms at the denuded skeleton/tissue interface, and analysis of microorganisms at local sites of infection reveal a group of bacteria, fungi, and microorganisms - all of which would be typical fauna of healthy corals. It is unaffected by antibiotics. Peters, in one study, found gram-negative rod shaped bacteria in the interstitial space in Acropora colonies with WBD (Peters 1984, 1997). Again, the correlation between WBD and these aggregates has remained elusive since previous attempts have also not been conclusive. Some suggestion of an algae correlation has been made, and also to one of temperature. Ritchie (1996, 1998) found a trend from Psuedomonas spp. to Vibrio spp. in the necrotic areas, and she asserts that Vibrio spp. may be better adapted to utilizing necrotic tissue for their growth. Follow up studies still continue in an attempt to isolate any potential bacteria and to determine if any causal relationships exist (Peters personal communication 1998). More recently, work in France suggests that the gram-negative areas are not bacteria but dense bodies found intracellularly at the base of the calicoblastic epithelium that may play a role in an self-mediated tissue sloughing (Guest et al. 1999).

Corals in an aquarium may also show signs of a white-band type loss of tissue. Stress from collection is likely to be partly causal. Any further changes, including the relatively high nutrient levels commonly found in reef aquariums, may mark the beginning of a white-band type infection in captive corals. Many report a slow recession from the base of small polyped and large polyped stony corals that seem to match the descriptions of WBD in the literature. Such recession of tissue often seems to be a result of the inherent stress of captivity, including inadequate lighting conditions inadequate water flow, or poor water quality. It has also been noticed that some corals (Montipora, Acropora, Pocillopora, Seriatopora sp. etc.) progress to a more rapid tissue slough similar to some of the descriptions below. I have also experienced the remission of apparent WBD after a period of stability within a low stress captive environment. Since there is currently no known pathogen associated with WBD, and (to my knowledge) no microscopic work-up for the previously described bacterial aggregates has been done in captive cases, ascribing a diagnosis of WBD in the aquarium are merely hypothetical.

White-Band Type II

White-Band Disease, Type II, causes a more rapidly advancing band of denuded tissue than the Type I WBD described above. Kim Ritchie has found a bacterium associated with this disease that may be causative, but no papers have been published to support it. Studies are still underway, but though the progression of WBD type I and II may appear similar, it is not yet known whether they are related, the same, or different (Cervino 1997).

White Plague Type I

This disease is characterized by a slow loss of tissue from the base and sides on non-Acroporid type corals. It typically affects massive corals (Colpophyllia, Mycetophyllia, and others), and has been under study since the late 1970's by Dr. Philip Dustan. Thus far, no causative role of pathogens has been isolated, though studies continue (Cervino 1997). Peters (personal communication) states that it resembles her own described stress-related necrosis in appearance.

 

[Eric Borneman]

White Plague Type II

White Plague Type II is one of the most widespread diseases in the Caribbean and Gulf of Mexico. It affects a number of genera of predominantly massive-type corals and is being studied by several researchers. Kim Ritchie and Laurie Richardson have isolated a new species of Sphingomonas bacterium from the skeleton/tissue interface that appears to play an active role in the progression of the disease. Unfortunately, it now appears that there may be more than one bacteria in different cases of White Plague, and a consortium may also be present. The original paper that identified the sample was based a problematic, very limited sample size (n=2) (Bruckner, pers comm). White Plague Type II is responsible for a rapid loss of tissue from affected corals, and there appears to be a seasonal component.

Yellow-Blotch Disease (YBD)

This disease (1994) has been found to affect the massive reef building star coral genus, Montastraea. It was first discovered in the Florida Keys, and is characterized by tissue necrosis resulting in a denuded skeleton and algal overgrowth. The receding tissue margins have a distinctive pale yellow band of variable width. The recession is not rapid and no causative pathogens have been isolated, although Cervino and Smith may have isolated a pathogen of the zooxanthellae (Cervino pers comm.). The unusual appearance of tissue and predictable histological changes would tend to indicate a specific causal element or vector (Cervino 1997, Peters 1997). Remissions do occur, and there may be a seasonal component in some locations.

Black-Band Disease (BBD)

First discovered over twenty five years ago by Antonius (1973), Black-Band disease (BBD) is one of the most well understood of coral diseases. While the initiating factors are not established, stress or injury seems to play a critical role (Antonius 1981, 1985, et. al., Peters 1993, 1997, et. al.). BBD affects many types of corals, from massive corals to small polyped corals and gorgonians, though degrees of resistance and total immunity are reported (Antonius 1984, 1985, 1988 et. al). It is transferable through close contact (Antonius 1985). Once established, a black band consisting of primarily Phormydium corallyticum, (a cyanobacteria), Spirulina sp. (a cyanobacteria), sulfide-reducing bacteria (responsible for the black color of the band), Beggiatoa sp. (a sulfur-oxidizing bacteria), ciliates, protozoans and other associated bacteria participate in the tissue degeneration activities of the advancing band (Peters 1997, et. al.). BBD occurs worldwide, although the mixture of organisms responsible for the black band may vary to some degree. P. corallyticum may be a constant associative cyanobacteria, and studies are underway to determine if this is the case (Antonius 1984, Peters 1997). BBD is rarely seen in the aquarium, though it is susceptible to the paste application of topical antibiotics and certain other treatment protocols (Antonius 1981, Delbeek and Sprung 1994, Borneman pers. obs.). On the other hand, local areas of tissue loss in both stony corals and octocorals frequently become covered by "slime algae." I have examined some of these cyanobacterial accumulations under a microscope and found that there are at least four different types of cyanobacteria that can accumulate on denuded skeletal areas in the aquarium, together with various protozoans and bacteria. Some are quite filamentous while others or more slimy or jelly-like. I suspect that the necrotic tissue simply provides substrate for those species in any individual tank that can utilize them efficiently, and that the "classic" accumulations of BBD seen in the wild may not be present. These areas may progress similar to a BBD or a RBD (below). While it is not known if they are the same, the equivalence in terms of their effect is pronounced.

Red-Band Disease (RBD)

A cyanobacterial association with octocorals, predominantly gorgonians, may be the cause of Red-Band Disease (RBD). Originally thought to be a BBD, RBD has been found to affect both octocorals and stony corals. P. corallyticum has not been found to be a species present in the cyanobacterial population. Rather, several cyanobacteria from the genus Schizothrix have been isolated from the centimeter-wide, dark red band at the margins of tissue loss in some studies, with cyanobacteria of the genus Oscillatoria discovered in microscopic exams of RBD affecting stony corals in the Bahamas. The band advances only during the day, and thus proceeds at a slower rate than BBD (Peters 1997).

Brown-Band Disease

Another recent band disease has been reported affecting numerous species of stony corals in the Great Barrier Reef. Brown-Band Disease was first reported in Acropora formosa. It appears that this is another cyanobacterial mediated progression, though its relation to either RBD or BBD has yet to be established (Peters 1997).

Yellow Band Disease

Recently reported from the Gulf of Oman in 1998, the corals found to afflicted are various Acropora spp, Porites spp., Turbinaria reninformis and Cyphastrea sp. In this disease, a broad yellow band, similar to BBD, is present but the denuded skeleton can remain yellow instead of white. It occurs more frequently and progresses faster in warmer months, and so far has been associated with corals located near sulfur mining operations. The nature of this disease seems to indicate that specific agents - either alone or in a consortium, will be found.