White band disease

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White band disease
Other namesAcroporid white syndrome
White band disease affecting elkhorn coral ("Acropora palmata") in Africa.
SpecialtyMarine biology

White band disease is a

acroporid corals and is distinguishable by the white band of exposed coral skeleton that it forms.[1] The disease completely destroys the coral tissue of Caribbean acroporid corals, specifically elkhorn coral (Acropora palmata) and staghorn coral (A. cervicornis).[1] The disease exhibits a pronounced division between the remaining coral tissue and the exposed coral skeleton.[2] These symptoms are similar to white plague, except that white band disease is only found on acroporid corals, and white plague has not been found on any acroporid corals.[3] It is part of a class of similar disease known as "white syndromes", many of which may be linked to species of Vibrio bacteria. While the pathogen for this disease has not been identified, Vibrio carchariae may be one of its factors. The degradation of coral tissue usually begins at the base of the coral, working its way up to the branch tips, but it can begin in the middle of a branch.[1]

Appearance

White Syndrome in the Indo-Pacific

White band disease causes the affected coral tissue to spin off the skeleton in a white uniform band for which the disease was given its name.

filamentous algae.[6]

There are two variants of white band disease, type I and type II.

Bahamas, does produce a margin of bleached tissue before it is lost.[7] Type II of white band disease can be mistaken for coral bleaching.[7] By examining the remaining living coral tissue for bleaching, one can delineate which type of the disease affects a given coral.[7]

Pathogen

No known

Vibrio carchariae population.[9][10] Histopathological examinations of diseased tissue provide some insight into the specific pathogen or combination of pathogens that cause this disease.[5] However, substantial samples of rickettsiales have been present in the surface layer, which causes scientists to suspect that this bacteria may be one of the factors of the disease.[5][10]

The disease, however, typically begins from the base of the coral and works its way up the coral branches.[1] As it progresses, the band leaves behind the white coral skeleton.[4] Many of the details of how the breakdown of coral occurs due to the bacteria are unclear mainly in part to the difficulty in isolating marine bacteria.[8] Studies have confirmed that white band disease is contagious and caused by a pathogenic bacteria.[8] Experiments have shown that Ampicillin may be able to treat white band disease type I.[8]

Impact and range

Since white band disease was first reported in the 1970s, the disease has led to the devastation of approximately 95% of the elkhorn and staghorn corals in the Caribbean region.

parrot-fish, snapper shrimps, and many other reef species, causing a sharp decline in the biodiversity of an affected region.[13] Coral reefs are also home to more than twenty-five percent of all marine fish species, making them extremely biologically diverse.[13] The loss of this coral would be particularly damaging to people living on the coast in terms of the food supply, coastal protection, economic security and more.[12] Nearly 500 million people directly depend on coral reefs for food and income (through tourism or otherwise).[12]

Elkhorn coral absorbs much carbon dioxide from the ocean every year, preventing

substratum space for further algal growth.[6] Prospects are poor for the recovery of the elkhorn coral, given its asexual method of reproduction, which relies on coral fragments breaking off from the main body and growing in a new area.[6] Staghorn coral also relies on asexual fragmentation as its primary method of reproduction, however, staghorn coral possesses a higher rate of sexual recruitment than Elkhorn coral.[6]

White band disease has been reported most notably in the Caribbean region.[6] However, white band disease has also been sighted in the Red Sea, and the Indo-Pacific region, including the Philippines, the Great Barrier Reef, and Indonesia.[15] Unlike white band disease in the Caribbean region, white band disease in the Indo-Pacific region has been found on approximately 34 species of massive, branching and plating corals instead of just simply Elkhorn and Staghorn corals.[15]

Transmission

White band disease is highly contagious through direct contact between diseased and healthy coral tissue.

fireworms, or other such aquatic organisms.[10] Waterborne transmission helps to explain how the disease spread across the Caribbean so rapidly, given that direct contact between affected corals is limited to physical interaction between the diseased and healthy coral and that the corallivorous snail, C. abbreviata that carries the disease, does not travel across long distances.[10]

Insights into the nature of white band disease transmission provide understanding of how the disease might be managed and controlled to prevent major losses in coral.[10] Waterborne transmission of white band disease may prove difficult to manage however, given the flowing nature of ocean currents.[10] An alternative method would be to control C. abbreviata populations to reduce the incidence of white band disease by manually removing samples of the population, similar to efforts to remove Pterois from the Gulf of Mexico.[10]

Effects of climate change

White band disease prevalence in the Caribbean varies seasonally.[10] It is more active in summer and less prominent in winter, suggesting that warmer water temperatures contribute to the waterborne spread of the disease to affected corals.[10] The impacts of climate change and increasing carbon emissions only serve to heat the waters surrounding the coral reef ecosystems, which may allow for the spread of diseases such as white band disease and others.[14] The severity of marine diseases such as white band disease increase for several reasons. Elevated water temperature can cause corals physiological stress.[14] This possibly undermines their immune systems and makes them more susceptible to infection from white band disease or other coral diseases.[14] Furthermore, elevated temperatures make bacterial and fungal pathogens much more virulent. However, the disease is not limited to elevated water temperatures as white band disease can still be prevalent even when water temperatures are cool.[10][13][14]

Anthropogenic

climate change is negatively impacting the world's corals and coral reef ecosystems. Over the next few decades as climate change continues, oceanic warming and acidification will accelerate and further damage the fragile reef ecosystems.[14] Prediction of the impacts of future climate change on coral reefs can be difficult given the uncertainty in certain involved socioeconomic factors (i.e. political response, future technology, changes in human behavior, the Earth's climate system, and the realtime effects on coral reefs).[14] Despite these uncertainties, humans could see the extinction of the coral reef ecosystem by the end of the 21st century if actions are not taken to protect them.[14] According to forecast models of increasing oceanic temperature, mass mortality events will likely occur as early as the summer of 2030 and continue to occur on an annual basis.[13][14]

See also

References

  1. ^ a b c d e f Gladfelter, W. B. "Population Structure of Acropora palmata on the Windward Fore Reef, Buck Island National Monument, St. Croix, U.S. Virgin Islands". U.S. Department of the Interior, National Park Service. {{cite web}}: Missing or empty |url= (help)
  2. ^ "White band disease".
  3. ^ Vargas-Angel, and Wheeler, Bernardo, and Benjamin. "Coral Health and Disease Assessment in the U.S. Pacific Territories and Affiliated States" (PDF).{{cite web}}: CS1 maint: multiple names: authors list (link)
  4. ^ a b c d "Major Reef-Building Coral Diseases". NOAA's Coral Reef Information System.
  5. ^ a b c Peters, E. C. "Diseases of coral reef organisms". Life and Death of Coral Reefs. Chapman & Hall. {{cite web}}: Missing or empty |url= (help)
  6. ^
    S2CID 34863063.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  7. ^ a b c Ritchie and Smith. "Type II White-Band Disease" (PDF).
  8. ^
    PMID 22355526
    .
  9. ^ Ritchie and Smith. "Preferential carbon utilization by surface bacterial communities by water mass, normal, and white band diseased Acropora cervicornis" (PDF).
  10. ^
    PMID 23150775.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  11. ^ a b c "Coral's Ecological Value".
  12. ^ a b c "Coral Reefs and Climate Change: Impacts on Humans".
  13. ^
    PMID 15150414.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  14. ^ a b c d e f g h i j Bruno, John. "Coral reefs and climate change".
  15. ^ a b Green, E. and A. W. Bruckner. "The significance of coral disease epizootiology for coral reef conservation". 96. Biological Conservation. {{cite web}}: Missing or empty |url= (help)

External links

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