About CRED » Ecological Assessment » Coral

Coral Health and Disease Assessment

Disease is defined as any impairment that interferes with or modifies the performance of normal physiological functions, including responses to environmental factors such as nutrients, toxicants, and climate; infectious agents; inherent or congenital defects; or a combination of these factors (Wobeser 2006). CRED has embarked on a long-term, broad-scale coral disease assessment and monitoring program aimed at documenting the prevalence of coral diseases on U.S. Pacific reefs and investigating factors that may be contributing to the occurrence of disease. With direct support from NOAA's Coral Reef Conservation Program, between 2006 and 2007, CRED conducted a total of 326 coral disease surveys at: Johnston and Wake Atolls, the Line and Phoenix Islands, American Samoa, the main Hawaiian Islands, the Northwestern Hawaiian Islands, Guam, and the Commonwealth of the Northern Mariana Islands (CNMI). Disease prevalence, for which no data existed in many of the U.S. Pacific jurisdictions prior to this project (e.g., Howland, Baker, and Jarvis Islands, Kingman Reef, Wake Atoll, and the CNMI), is now better characterized, and a better understanding of disease occurrence and potential impacts on U.S. Pacific coral reefs is emerging.

Description and status of commonly recognized coral lesions and diseases on the U.S. Pacific Territories

Lesions involving tissue loss
Acute Tissue Loss (white syndrome) Description: This is a collective term to describe lesions characterized by the rapid loss of tissue, leaving behind a sharp, clean band, where tissue is completely removed from the skeleton. A progression of filamentous and turf algae generally covers the exposed skeleton. Our assessments have recorded white syndrome on at least 6 Pacific genera representing 4 scleractinian families, with species of Acropora and Montipora being the most common hosts. In the Northwestern Hawaiian Islands this disease is lethal to tabular acroporids. Distribution and abundance: Occasional to common at Johnston Atoll and French Frigate Shoals (Northwestern Hawaiian Islands); occasional in the Line Islands and the main Hawaiian Islands uncommon to rare elsewhere.
Sub-acute Tissue Loss Description: We use this collective term to describe lesions resulting in slow but progressive loss of tissue. Sub-acute tissue loss is distinguished from white syndrome by the narrow width of the zone of recently exposed skeleton. Because a particular type of gross lesion can present multiple microscopic manifestations, coral disease assessments and studies require biopsies for histological, microbiological, and molecular evaluation and verification. Distribution and abundance: Occasional sightings in Guam, the CNMI, Line Islands and Hawaiian Archipelago; rare elsewhere.
Alcyonarian Necrosis Description: Lesions are variable in size but generally characterized by irregular patches of exposed skeleton flanked by a zone of degenerating tissue, of variable width. In some cases, discolored tissue flanks the black margin of active tissue loss, suggesting an already compromised health state. Distribution and abundance: Very rare; only two cases, at Palmyra Atoll.
Lesions involving discoloration and tissue loss
Endolithic Fungal Infection (mycosis) Description: Patchy dark discolorations occurring in irregular patterns scattered on the coral surface. Most commonly observed on a variety of encrusting taxa including Pavona, Porites, Leptastrea, and Cyphastrea. Microscopic examination of tissues reveals extensive endolithic fungal proliferation. In Porites, upward migration of fungal hyphae into the thecal cavity is generally associated with disruption of the polyp body wall and sloughing of gastrodermis. Distribution and abundance: Rare to occasional; cases reported for the main Hawaiian Islands, Northwestern Hawaiian Islands, American Samoa, Guam, the CNMI, and Line Islands.
Black Band Disease Description: This condition is characterized by a distinct black mat, ~0.5 to 4 cm wide, on the living coral tissue, leaving behind the bare white skeleton. The unaffected coral tissue appears normal in color and morphology. Research indicates that there is a lack of concordance in the cyanobacterial species associated with the microbial consortium of black band disease between Caribbean and Indo-Pacific coral taxa (see Willis et al. 2004). Distribution and abundance: Very rare; only one sighting registered in American Samoa.
Banded Fungal Infection Description: Diseased colonies exhibit a distinct yellow to bright green mat about ~1 to 3 cm wide on the coral tissue. A progression of filamentous and turf algae generally appears on the exposed skeleton as the tissue is lost. As in black band disease, the unaffected coral tissue appears normal in color and morphology. Microscopic examination of diseased tissue reveals that the microbial mat is mainly composed of fungal hyphae. Distribution and abundance: Very rare; only two sightings registered, one in the CNMI and the other at Palmyra Atoll.
Tissue discoloration not necessarily associated with tissue loss
Bleaching Description: Our disease assessments tally colonies exhibiting full, partial, or spotty bleaching. This condition is the result of a reduction in the intensity or complete absence of coloration within the coral tissues, due to loss of pigmentation in, and/or expulsion of the endosymbiotic zooxanthellae. Bleaching has been attributed to exposure to increased water temperatures. However, high levels of ultraviolet radiation, salinity, turbidity, and sedimentation may also induce bleaching. Although bleaching is considered a generalized response to stressful conditions, it is a sign of disease when it results in an impairment or inhibition of normal coral functioning (e.g., growth, calcification, reproduction) and colony death. Recent studies also indicate that bleaching can be caused by an intracellular bacterial pathogen of the genus Vibrio. Distribution and abundance: Temperature-related widespread bleaching has been observed in Northwestern Hawaiian Islands (Aeby et al. 2003). Patchy, focal bleaching is occasional to rare elsewhere.
Trematodiasis Description: Pink to pale, about ~5 mm in diameter protuberances, focal or widely distributed on the coral surface. These are caused by an encysted parasitic digenetic trematode. The main host for this disease is the genus Porites. Distribution and abundance: Infected colonies are occasional to abundant in the main and Northwestern Hawaiian Islands; absent elsewhere.
Hyper-pigmented Irritations - Pink Line/Spot Description: This type of response appears only in the Indo-Pacific Poritidae. Lesions are characterized by bright pink patches of discolored, swollen tissue, often occurring in irregular shapes and patterns, scattered on the surface of the colony or adjacent to the sediment/algal margins of a colony. Often, but not exclusively, lesions appear to be associated with small areas of tissue loss or filamentous algal infections; however, uncomplicated lesions are also common. Distribution and abundance: Lesions are common in the main Hawaiian Islands, Guam, and the southern CNMI; occasional elsewhere.
Lesions involving skeletal growth anomalies
Tumors Description: Lesions characterized by changes in normal shape or form of coral colonies; unusual growths and/or protuberances associated with an abnormal deposition of the skeleton. Skeletal growth anomalies are caused by changes in the coral cells that deposit the carbonate skeleton. Such changes are: 1) Hyperplasia: a process resulting in an increase in the number of cells in a tissue or organ, thereby increasing the bulk of the tissue or the organ; 2) Neoplasia: a pathology resulting in the formation and growth of an undifferentiated mass of cells that continues after the cellular stimulus ceases. Distribution and abundance: Coral tumors and skeletal growth anomalies are common to abundant in the main Hawaiian Islands and Johnston Atoll; occasional elsewhere.
Other lesions
Coral-algae and other biotic interactions may result in an impairment or inhibition of normal coral functioning (e.g., growth, calcification, reproduction). These morphologies, together with barnacle and tube worm infestations, as well as other unidentified cases are grouped under 'other lesions' in our disease prevalence surveys.

Lesions involving tissue loss

Acute Tissue Loss (white syndrome)

Description: This is a collective term to describe lesions characterized by the rapid loss of tissue, leaving behind a sharp, clean band, where tissue is completely removed from the skeleton. A progression of filamentous and turf algae generally covers the exposed skeleton. Our assessments have recorded white syndrome on at least 6 Pacific genera representing 4 scleractinian families, with species of Acropora and Montipora being the most common hosts. In the Northwestern Hawaiian Islands this disease is lethal to tabular acroporids.

Distribution and abundance: Occasional to common at Johnston Atoll and French Frigate Shoals (Northwestern Hawaiian Islands); occasional in the Line Islands and the main Hawaiian Islands uncommon to rare elsewhere.

Sub-acute Tissue Loss

Description: We use this collective term to describe lesions resulting in slow but progressive loss of tissue. Sub-acute tissue loss is distinguished from white syndrome by the narrow width of the zone of recently exposed skeleton. Because a particular type of gross lesion can present multiple microscopic manifestations, coral disease assessments and studies require biopsies for histological, microbiological, and molecular evaluation and verification.

Distribution and abundance: Occasional sightings in Guam, the CNMI, Line Islands and Hawaiian Archipelago; rare elsewhere.

Alcyonarian Necrosis

Description: Lesions are variable in size but generally characterized by irregular patches of exposed skeleton flanked by a zone of degenerating tissue, of variable width. In some cases, discolored tissue flanks the black margin of active tissue loss, suggesting an already compromised health state.

Distribution and abundance: Very rare; only two cases, at Palmyra Atoll.

Lesions involving discoloration and tissue loss

Endolithic Fungal Infection (mycosis)

Description: Patchy dark discolorations occurring in irregular patterns scattered on the coral surface. Most commonly observed on a variety of encrusting taxa including Pavona, Porites, Leptastrea, and Cyphastrea. Microscopic examination of tissues reveals extensive endolithic fungal proliferation. In Porites, upward migration of fungal hyphae into the thecal cavity is generally associated with disruption of the polyp body wall and sloughing of gastrodermis.

Distribution and abundance: Rare to occasional; cases reported for the main Hawaiian Islands, Northwestern Hawaiian Islands, American Samoa, Guam, the CNMI, and Line Islands.

Black Band Disease

Description: This condition is characterized by a distinct black mat, ~0.5 to 4 cm wide, on the living coral tissue, leaving behind the bare white skeleton. The unaffected coral tissue appears normal in color and morphology. Research indicates that there is a lack of concordance in the cyanobacterial species associated with the microbial consortium of black band disease between Caribbean and Indo-Pacific coral taxa (see Willis et al. 2004).

Distribution and abundance: Very rare; only one sighting registered in American Samoa.

Banded Fungal Infection

Description: Diseased colonies exhibit a distinct yellow to bright green mat about ~1 to 3 cm wide on the coral tissue. A progression of filamentous and turf algae generally appears on the exposed skeleton as the tissue is lost. As in black band disease, the unaffected coral tissue appears normal in color and morphology. Microscopic examination of diseased tissue reveals that the microbial mat is mainly composed of fungal hyphae.

Distribution and abundance: Very rare; only two sightings registered, one in the CNMI and the other at Palmyra Atoll.

Tissue discoloration not necessarily associated with tissue loss

Bleaching

Description: Our disease assessments tally colonies exhibiting full, partial, or spotty bleaching. This condition is the result of a reduction in the intensity or complete absence of coloration within the coral tissues, due to loss of pigmentation in, and/or expulsion of the endosymbiotic zooxanthellae. Bleaching has been attributed to exposure to increased water temperatures. However, high levels of ultraviolet radiation, salinity, turbidity, and sedimentation may also induce bleaching. Although bleaching is considered a generalized response to stressful conditions, it is a sign of disease when it results in an impairment or inhibition of normal coral functioning (e.g., growth, calcification, reproduction) and colony death. Recent studies also indicate that bleaching can be caused by an intracellular bacterial pathogen of the genus Vibrio.

Distribution and abundance: Temperature-related widespread bleaching has been observed in Northwestern Hawaiian Islands (Aeby et al. 2003). Patchy, focal bleaching is occasional to rare elsewhere.

Trematodiasis

Description: Pink to pale, about ~5 mm in diameter protuberances, focal or widely distributed on the coral surface. These are caused by an encysted parasitic digenetic trematode. The main host for this disease is the genus Porites.

Distribution and abundance: Infected colonies are occasional to abundant in the main and Northwestern Hawaiian Islands; absent elsewhere.

Hyper-pigmented Irritations - Pink Line/Spot

Description: This type of response appears only in the Indo-Pacific Poritidae. Lesions are characterized by bright pink patches of discolored, swollen tissue, often occurring in irregular shapes and patterns, scattered on the surface of the colony or adjacent to the sediment/algal margins of a colony. Often, but not exclusively, lesions appear to be associated with small areas of tissue loss or filamentous algal infections; however, uncomplicated lesions are also common.

Distribution and abundance: Lesions are common in the main Hawaiian Islands, Guam, and the southern CNMI; occasional elsewhere.

Lesions involving skeletal growth anomalies

Tumors

Description: Lesions characterized by changes in normal shape or form of coral colonies; unusual growths and/or protuberances associated with an abnormal deposition of the skeleton. Skeletal growth anomalies are caused by changes in the coral cells that deposit the carbonate skeleton. Such changes are: 1) Hyperplasia: a process resulting in an increase in the number of cells in a tissue or organ, thereby increasing the bulk of the tissue or the organ; 2) Neoplasia: a pathology resulting in the formation and growth of an undifferentiated mass of cells that continues after the cellular stimulus ceases.

Distribution and abundance: Coral tumors and skeletal growth anomalies are common to abundant in the main Hawaiian Islands and Johnston Atoll; occasional elsewhere.

Other lesions

Coral-algae and other biotic interactions may result in an impairment or inhibition of normal coral functioning (e.g., growth, calcification, reproduction). These morphologies, together with barnacle and tube worm infestations, as well as other unidentified cases are grouped under 'other lesions' in our disease prevalence surveys.

References and related links

Aeby G.S., J.C. Kenyon, J.E. Maragos, D.C. Potts

(2003) First record of mass coral bleaching in the Northwestern Hawaiian Islands. Coral Reefs 22:256.

Willis B.L., C. Page, E. Dinsdale

(2004) Coral Diseases on the Great Barrier Reef. Pages 69-104 in E. Rosenberg and Y. Loya, eds. Coral Health and Disease, Springer-Verlag, Berlin, 488p.

Wobeser G.A.

(2006) Essentials of disease in wild animals. Blackwell Publishing Professional, Ames, Iowa, U.S.A. 243p.

Work T.M., G.S. Aeby

(2006a) Diseases of Hawaiian corals. Underwater identification cards. Funded partly by Bishop Museum, Hawaii Coral Reef Initiative, Hawaii Division of Aquatic Resources, Hawaii Institute of Marine Biology, and U.S. Geological Survey.

Work T.M., G.S. Aeby

(2006b) Faamai o amu a American Samoa (Diseases of American Samoa corals). Underwater identification cards. Funded partly by: Bishop Museum, Hawaii Coral Reef Initiative, Hawaii Division of Aquatic Resources, Hawaii Institute of Marine Biology, and U.S. Geological Survey.

Coral Disease and Health Consortium (CDHC)

Coral Disease Identification and Information (NOAA's Coral Health and Monitoring Program)

http://ourworld.compuserve.com/homepages/mccarty_and_peters/Coraldis.htm

CRED MENU

CRED HIGHLIGHTS

Coral Reef Ecosystem Monitoring Report for American Samoa (2002-2006): The Coral Reef Ecosystem Division has completed a report of the extensive Reef Assessment and Monitoring Program (RAMP) research conducted in American Samoa by PIFSC scientists and their partners during 2002-2006. The report has been published (PIFSC Special Publication, SP-08-002) and is now available online. Click here to view the report.