Coral Reef Ecosystem Division's field assessment of Indo-Pacific coral diseases and compromised health states

Overview of Coral and Algal Diseases
Type of Lesion Lesion Category Lesion Name
Tissue loss Predation
Non-predation: white syndromes
Non-predation: colored bands
Tissue discoloration White
Non-white
Skeletal growth anomalies Skeletal growth anomalies
Other Aggressive infestations/overgrowth:
  • Algal overgrowth
  • Cyanophyte overgrowth
  • Sponge (Terpios) overgrowth
  • Barnacle infestation
  • Tubeworm infestation
  • Flatworm infestation
  • Sediment damage
  • Alcyonarian necrosis
Coralline Algal Diseases Coralline Algal Diseases

Tissue Loss

Predation

Crown-of-thorns Seastar (Acanthster planci Predation

Description: Conspicuous scars, forming focal-to-diffuse tissue loss lesions that expose the bare coral skeleton. Recent lesions are white and generally exhibit discrete borders.

Distribution and abundance: Occasional to common on reefs with populations of crown-of-thorns seastars (COTS)

Snail Predation

Description: Focal, multifocal, or diffuse scars that expose the bare coral skeleton. Recent lesions are white and generally exhibit discrete, scalloped borders; hazy, pale borders are not uncommon, however.

Non-predation: White Syndromes

Acute Tissue Loss

Description: This term is a collective one used to describe lesions characterized by the rapid loss of tissue that leaves 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 six Pacific genera representing four 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 at French Frigate Shoals (Northwestern Hawaiian Islands), occasional at Kingman Reef, Palmyra Atoll, and Jarvis Island and in the main Hawaiian Islands, and uncommon to rare elsewhere.

Subacute Tissue Loss

Description: We use this collective term to describe lesions that result in slow but progressive loss of tissue. Subacute 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, and Hawaiian Archipelago and at Kingman Reef, Palmyra Atoll, and Jarvis Island; rare elsewhere.

Non-predation: Colored Bands

Banded Fungal Infection

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

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

Black Band Disease

Description: This condition is characterized by a distinct black mat, ~ 0.5-4 cm wide, on living coral tissue, leaving behind a 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.

Cyanophyte Infection

Cyanophyte Infection Cyanophyte Infection
Photos by Darla White, DAR Hawaii.

Description: Lesions are variable in shape and size and are characterized by a diffuse grey to black band or patch ~ 0.5 to 3 cm wide of flocculent material, separating the healthy tissue from the exposed coral skeleton. The unaffected coral tissue appears normal in color and morphology; lesions exhibit a semi-circular to amorphous pattern of tissue loss. Generally, filamentous and turf algae appear on the exposed skeleton as tissue is lost.

Distribution and abundance: Rare, with sightings registered around the main Hawaiian Islands (Kauaʻi, Maui and Hawaiʻi), affecting preferentially Montipora capitata, M. flabellata, and M. patula. An outbreak of this disease has resulted in widespread mortality of Montipora corals in Hanalei Bay (Kauaʻi).

Tissue Discoloration

White

Patchy Bleaching

Patchy Bleaching Patchy Bleaching
Patchy bleaching—multifocal spots (left) and focal stripe (right).

Description: Patchy bleaching usually occurs as focal to multifocal discrete patches of absent or reduced pigmentation; it can be distinguished from thermal bleaching, which is generally widespread reef-wide, typically affecting the upper to entire colony surfaces. Recent studies also indicate that patchy bleaching can be caused by intracellular bacterial pathogens of the genus Vibrio.

Distribution and abundance: Although not rare, patchy bleaching is occasional to uncommon.

Thermal Bleaching

Thermal Bleaching Thermal Bleaching
Left: thermal bleaching at Howland in the Pacific Remote Island Areas. Right: thermal bleaching at Kure Atoll, Northwestern Hawaiian Islands .NOAA photos by Bernardo Vargas-Ángel and Jason Helyer.

Description: This condition is the result of a reduction in the intensity or complete absence of coloration within coral tissues, due to loss of pigmentation in 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, and reproduction) and colony death.

Extensive, severe coral bleaching, also known as thermal bleaching, generally coincides with abnormally high and persistent sea-surface temperatures. Since 1979, nine major coral bleaching episodes have affected important coral reef provinces around the world.

Distribution and abundance: Widespread, thermal bleaching has been observed at Howland and Baker Islands as well as at Pearl and Hermes, Midway, and Kure Atolls and Lisianski Island in the Northwestern Hawaiian Islands (Aeby et al. 2003).

Non-white

Endolithic Hypermycosis

Description: Patchy dark discolorations that occur in irregular patterns scattered on the surface of corals. 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, with cases reported for the main Hawaiian Islands, Northwestern Hawaiian Islands, American Samoa, Guam, the CNMI, and Kingman Reef, Palmyra Atoll, and Jarvis Island.

Pigmentation Response

Description: This type of response appears only in the Indo-Pacific Poritidae. Lesions are characterized by bright pink patches of discolored, swollen tissue that often occur in irregular shapes and patterns, scattered on the surface of the colony or adjacent to the sediment or 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 also are common.

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

Trematodiasis

Description: Pink to pale protuberances ~ 5 mm in diameter that are focal or widely distributed on the coral surface. These lesions 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.

Skeletal Growth Anomalies

Skeletal Growth Anomalies

Tumors

Description: Lesions characterized by changes in normal shape or form of coral colonies; changes include unusual growths 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. Changes fall into two main groups: 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 at Johnston Atoll; occasional elsewhere.

Other

Aggressive Infestations/Overgrowth

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

Distribution and abundance: These various conditions range from occasional to abundant throughout the US. Pacific Islands and Territories. They tend to be more common on reefs adjacent to human settlements or areas that are subject to some type of environmental stress.

Alcyonarian necrosis

Description: Lesions are variable in size but generally characterized by irregular patches of exposed skeleton flanked by a variable-width zone of degenerating tissue. 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.

Coralline Algal Diseases

Coralline Algal Diseases

Although not coral, crustose coralline algae are included here because of their importance to coral reef environments. Similar to corals, coralline algae deposit layers of calcium carbonate and are important reef-builders. In addition, because crustose coralline algae provide essential chemical cues and substrate for coral larval recruitment, destruction of this group due to disease has the potential to significantly affect the development and recovery of coral reefs.

Coralline Cyanophyte Disease

Description: Irregularly shaped patches or bands of slimy, fuzzy, green or tan cyanobacterial material that spreads across the algal surface and leaves behind the bare carbonate skeleton; turf and filamentous algae often colonize the bare coralline tallus. Commonly, lesions are distinguishable not only by the conspicuous appearance of the cyanobacterial mat but also because bright red, orange, or green, discolored coralline tallus is observable in areas where the mat has been lifted or disrupted. The etiology of this disease is still largely unknown.

Distribution and abundance: Very rare; only a few sightings in American Samoa and the CNMI.

Coralline Fungal Disease

Description: Characteristics are unlike any other fungal pathogen or black band disease and are denoted by striated bands that are non-glossy with a blue-black color and matte texture (Littler and Littler 1998). At the time when it was first discovered in American Samoa, this disease co-occurred with coralline lethal orange disease and also primarily attacked Porolithon onkodes.

Distribution and abundance: Common to abundant at Swains Island in American Samoa and at Kingman Reef and Palmyra Atoll; rare elsewhere.

Coralline Lethal Orange Disease

Coralline Lethal Orange Disease Coralline Lethal Orange Disease
NOAA photo by Erin Looney.

Description: Characterized by a band of bright orange, slimy, stringy material that is spread across the surface of algae and leaves behind the skeletal carbonate remains of algae; turf and filamentous algae often colonize the bare coralline thallus. Individual lesion sizes vary considerably but typically range from 1 to 10 cm in maximum diameter. CLOD is a bacterial disease first reported by Mark and Diane Littler in 1993 on South Pacific coral reefs (Littler and Littler 1995). It appears that the CLOD pathogen is highly virulent and the orange material is easily transferable and, therefore, can infect other plants (Littler and Littler 1995). A consortium of five bacterial species have been consistently identified as associated within the CLOD condition — these species are closely related to the genera Planococcus, Bacillus, and Pseudomonas (Cervino et al. 2005).

Distribution and abundance: CLOD is the most abundant of the five coralline-algal diseases identified by CRED. This disease occurs most frequently around American Samoa and Guam but also occurs in lower abundances in the CNMI and Northwestern Hawaiian Islands.

Coralline Target Phenomena

Description: This term is a collective one used to describe lesions characterized by discolored (white, light yellow, or pale green), concentric, annular or horseshoe-shaped bands that measure 0.5-3 cm in width, radiate from a focal point, and leave behind the bare skeletal carbonate remains of coralline algae. Lesions can range from a few centimeters up to 100 cm in maximum diameter. Littler and Littler (2003) propose that these conspicuous lesion shapes are probably formed by patterns of thallus death and regrowth. The etiological aspects of this disease are still poorly understood.

Distribution and abundance: Occasional to rare.

Coralline White Band Syndrome

Description: This term is a collective one used to describe poorly characterized lesions typified by a loss of tissue that leaves behind a sharp, clean, white band (1–3 cm wide) where the dead coralline thallus is exposed. Often, but not exclusively, the edges of spreading lesions exhibit a thin (~ 0.5 cm wide) band of discolored yellow, green, or pink tissue. Earlier referred to as "coralline lethal disease", this condition was first recognized by Tom Goreau in the Caribbean in 1996, with more recent observations across the Indian Ocean and off the Philippines. The etiology of this disease is still largely unknown.

Distribution and abundance: Occasional to rare with sightings in American Samoa, the CNMI, Palmyra Atoll, and Jarvis Island.

References cited and other related resources

Aeby GS, Kenyon JC, Maragos JE, Potts DC
2003. First record of mass coral bleaching in the Northwestern Hawaiian Islands. Coral Reefs 22: 256.
Cervino JM, Littler MM, Littler DS, Polson S, Goreau TJ, Brooks B, Smith GW
2005. Identification of microbes associated with coralline lethal algal disease and its relationship to glacial ice melt (global warming). Phytopathology 95(6): 120-121, S120 Publication No. P-2005-0005-SSA.
Littler M, Littler D
1995. Impact of CLOD pathogen on Pacific coral reefs. Science 267: 1356-60.
Littler M, Littler D
1998. An undescribed fungal pathogen of reef-forming crustose coralline algae discovered in American Samoa. Coral Reefs 17: 144.
Littler MM and Littler DS
2003. South Pacific reef plants: a diver’s guide to plant life of South Pacific coral reefs. Offshore Graphics, Washington DC, 330 pp
Raymundo LJ, Couch CS, Harvell DC (eds.)
2008. Coral disease handbook: guidelines for assessment, monitoring, and management. Currie Communications, Melbourne, Australia, 98p + Appendix.
Vargas-Ángel B
2010. Crustose coralline algal diseases in the U.S.-Affiliated Pacific Islands. Coral Reefs 29: 943–956.
Willis BL, Page C, Dinsdale E
2004. Coral diseases on the Great Barrier Reef. In: Rosenberg E and Loya Y (eds.). Coral health and disease, pp. 69-104. Springer-Verlag, Berlin.
Wobeser GA
2006. Essentials of disease in wild animals. Blackwell Publishing Professional, Ames, Iowa 243 p.
Work TM, Aeby GS
2006a. Diseases of Hawaiian corals. Underwater identification cards. Funded partly by Bishop Museum, Hawai`i Coral Reef Initiative, Hawaii Division of Aquatic Resources, Hawai`i Institute of Marine Biology, and U.S. Geological Survey.
Work TM, Aeby GS
2006b. Faamai o amu a American Samoa (Diseases of American Samoa corals). Underwater identification cards. Funded partly by Bishop Museum, Hawaii Coral Reef Initiative, Hawai`i Division of Aquatic Resources, Hawai`i Institute of Marine Biology, and U.S. Geological Survey.


For more information about CRED surveys for coral and algal diseases, contact Bernardo Vargas-Ángel. Also, additional information on coral disease can be found at these websites:

*All photos are NOAA photos by Bernardo Vargas-Ángel, except where noted.