White pox disease

White pox disease on Elkhorn coral

White pox disease (also called acroporid serratiosis and "patchy necrosis"), first noted in 1996 on coral reefs near the Florida keys, is a coral disease affecting Elkhorn coral (Acropora palmata) throughout the Caribbean. It causes irregular white patches or blotches on the coral that result from the loss of coral tissue. These patches distinguish white pox disease from white band disease which produces a distinctive white band where the coral skeleton has been denuded. The blotches caused by this disease are also clearly differentiated from coral bleaching and scars caused by coral-eating snails.^[1] It is very contagious, spreading to nearby coral.^[2]

At the locations where white pox disease has been observed, it is estimated to have reduced the living tissue in elkhorn corals by 50-80%.^[3] In the Florida Keys National Marine Sanctuary (FKNMS), the losses of living coral are estimated to average 88%.^[1] Elkhorn coral was formerly the dominant shallow water reef-building coral throughout the Caribbean but now is listed as a threatened, due in part to disease.^[4] This is the first species of coral to be listed as threatened in the United States.^[5]

Pathogen

S. marcescens on an agar plate

The pathogen responsible has identified as Serratia marcescens, a common fecal intestinal bacterium found in humans and other animals.^[1][6] This is the first time it has been linked to the death of coral.^[7] The specific source of the bacteria that is killing the coral is currently unknown. As well as living in animal and human intestines, S. marcescens can live in soil and water as an independent microbe.^[7]

The causes for the majority of known coral diseases have not been identified.^[8] It is of vital importance to understand the relationship between coral health and environmental factors in the study of coral disease.^[9] Much more research is needed to examine the variety of potential sources for genotypes similar to the Serratia pathogen. Possible sources include the effluents of waste water and septic tanks, as well as reef fishes feces and seabird guano. The human origin of the white pox bacteria must be determined before the managers of coral reef ecosystems and waste water treatment engineers can work toward finding a solution.^[1]

See also

• White band disease The cause of this disease remains unknown.
• Brown band disease AKA Red band disease, probably caused by ciliates (possibly Helicostoma nonatum) and cyanobacteria.
• Yellow-band disease AKA Yellow blotch disease.
• Skeletal Eroding Band, caused by the ciliate Halofolliculina corallasia.
• White plague, caused by the bacterium Aurantimonas coralicida.
• Black necrosing syndrome AKA Dark spots disease, probably caused by a fungus.
• Rapid Wasting, possibly caused by a fungus growing on areas damaged by feeding action of the parrotfish Sparisoma viride.
• Black band disease, caused by a microbial consortium dominated by the cyanobacteria Phormidium corallyticum.
• Aspergillosis, caused by the fungus Aspergillus sydowii, affects Gorgonian soft corals commonly known as sea fans.

Notes

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