Comprehensive Guide to Coral Diseases

Coral diseases are a significant threat to both wild and aquarium corals. These diseases can spread quickly, causing coral degradation, tissue loss, and even death if left untreated. Whether you are a hobbyist or a marine biologist, understanding these diseases and how to treat or prevent them is crucial for maintaining coral health. Below is a detailed guide on the most common coral diseases and pests, including their causes, symptoms, and treatment options.

1. White Band Disease (WBD)

White Band Disease primarily affects Acropora species such as staghorn and elkhorn corals. It is characterized by a white band of dead tissue that starts at the base of the coral and progresses upward.

• Causes: Thought to be caused by bacteria, though the exact pathogen is unclear. Environmental stressors such as poor water quality contribute.
• Symptoms: White bands of dead tissue that gradually expose the coral skeleton.
• Treatment: In aquarium settings, improve water quality and use antibacterial treatments. Frag healthy parts of the coral to save unaffected tissue.

2. Black Band Disease (BBD)

Black Band Disease is caused by cyanobacteria and affects a variety of coral species, including brain and staghorn corals. A black or dark brown band moves across the coral, killing tissue as it advances.

• Causes: A microbial consortium dominated by cyanobacteria, sulfide-oxidizing bacteria, and other microbes.
• Symptoms: A visible black band that moves across the coral, leaving dead tissue behind.
• Treatment: Improve water quality, reduce nutrient levels, and use targeted antibacterial treatments or hydrogen peroxide.

3. Red Band Disease (RBD)

Similar to Black Band Disease but distinguished by the presence of red-colored cyanobacteria. It primarily affects massive corals like brain corals.

• Causes: A combination of environmental stress and cyanobacteria overgrowth.
• Symptoms: Red bands of bacteria that slowly spread across the coral’s tissue.
• Treatment: Reducing nutrient levels and using antibacterial treatments or cyanobacteria removers can be effective.

4. White Plague (WP)

White Plague causes rapid tissue loss in stony corals, often starting from the base and moving outward.

• Causes: Bacterial infection, often linked to environmental stress and poor water conditions.
• Symptoms: A white area of tissue loss that rapidly spreads, exposing the skeleton.
• Treatment: Quarantine affected corals and use antibacterial treatments to stop the disease from spreading.

5. White Spot Disease

White Spot Disease affects both hard and soft corals and is characterized by the appearance of small white spots or lesions on the coral’s tissue.

• Causes: Stress from environmental changes or parasitic infections.
• Symptoms: Small white spots scattered across the coral.
• Treatment: Improve water quality and treat with iodine dips or other antiseptics.

6. Rapid Tissue Necrosis (RTN)

RTN is a devastating condition that causes coral tissue to slough off the skeleton in a matter of hours. It primarily affects small polyp stony (SPS) corals like Acropora.

• Causes: Environmental stress, bacterial infections, or sudden changes in water chemistry.
• Symptoms: Rapid tissue loss, often within hours, leaving exposed skeleton.
• Treatment: Immediate fragging of healthy coral tissue may save part of the colony. Stabilize water parameters and use antibacterial treatments.

7. Slow Tissue Necrosis (STN)

STN is similar to RTN but progresses more slowly, causing gradual tissue loss over days or weeks.

• Causes: Often linked to bacterial infections and environmental stressors like unstable water conditions.
• Symptoms: Slow, progressive tissue loss starting at the base of the coral and moving upward.
• Treatment: Stabilize water parameters and consider using bacterial treatments. Frag healthy tissue to preserve the coral.

8. Yellow Band Disease (YBD)

Yellow Band Disease is characterized by a yellow discoloration that spreads across the coral’s tissue, killing it as it advances. It primarily affects Caribbean reef-building corals.

• Causes: Bacterial pathogens and environmental stress.
• Symptoms: A yellow band or discoloration that moves across the coral, leading to tissue death.
• Treatment: Improve water quality and use antibacterial treatments to slow the spread.

9. Skeletal Eroding Band (SEB)

Skeletal Eroding Band is caused by protozoans, such as Halofolliculina, which erode the coral’s skeleton, leaving a white band of dead tissue.

• Causes: Protozoan infections.
• Symptoms: A white band that progresses across the coral, eroding the skeleton.
• Treatment: Improving water flow and reducing nutrient levels can help slow the spread of SEB.

10. Brown Jelly Disease

Brown Jelly Disease affects LPS corals such as hammer, frogspawn, and torch corals. It is characterized by a brown, jelly-like substance that rapidly destroys coral tissue.

• Causes: Protozoan infections, often triggered by injuries or environmental stress.
• Symptoms: Brown, jelly-like substance covering parts of the coral, followed by rapid tissue degradation.
• Treatment: Fragging affected areas and using iodine dips can help. Improving water quality is critical.

11. Coral Bleaching

Coral Bleaching occurs when corals expel their symbiotic zooxanthellae, resulting in a pale or completely white appearance. This makes corals more susceptible to disease.

• Causes: High water temperatures, excessive light, or other environmental stressors.
• Symptoms: Corals lose their color, turning pale or white.
• Treatment: Lower water temperatures and adjust light levels to help the coral recover. Maintaining stable conditions is crucial.

12. Fungal Infections

Fungal infections can occur in both hard and soft corals, leading to tissue damage and discoloration.

• Causes: Poor water conditions or injury to the coral.
• Symptoms: Discoloration, tissue loss, or the appearance of fungal growth on the coral.
• Treatment: Use antifungal treatments and improve water quality to prevent the spread of the infection.

13. Pink Line Syndrome

Pink Line Syndrome is characterized by a pink line or band that forms on the coral’s skeleton, typically around the base of SPS corals like Acropora.

• Causes: Linked to environmental stress and poor water conditions.
• Symptoms: A pink line or band at the base of the coral.
• Treatment: Improve water parameters and use appropriate antibacterial treatments.

14. Brown Band Disease

Brown Band Disease, also known as Ciliate Protozoan Infection, affects hard corals and is caused by ciliates, protozoans that feed on coral tissue, leaving behind a brown trail.

• Causes: Protozoan infections, often in weakened or stressed corals.
• Symptoms: A brown band of tissue destruction, progressing from the base to the tips of coral branches.
• Treatment: Remove infected tissue, improve water conditions, and use treatments like iodine dips.

15. Yellow Blotch Disease

Yellow Blotch Disease primarily affects massive reef-building corals. It appears as yellow blotches that slowly spread across the coral, killing tissue as it advances.

• Causes: Likely bacterial pathogens, exacerbated by environmental stressors.
• Symptoms: Yellow blotches on the coral’s surface, followed by tissue death.
• Treatment: Improve water quality and use antibacterial treatments to prevent further tissue loss.

16. Hyperplasia

Hyperplasia, also known as “coral tumors,” occurs when coral tissue begins to grow abnormally, forming bumps or nodules on the coral’s surface.

• Causes: Genetic mutations or environmental stressors like UV radiation or pollution.
• Symptoms: Abnormal growths or lumps on the coral’s tissue.
• Treatment: No specific treatments exist, but improving water conditions can slow the growth of hyperplasia.

17. White Pox Disease

White Pox is a highly contagious bacterial infection that causes rapid tissue loss in stony corals, particularly affecting elkhorn corals.

• Causes: The bacterium Serratia marcescens, commonly found in human sewage.
• Symptoms: Rapid tissue loss, leaving the coral’s skeleton exposed.
• Treatment: Quarantine affected corals and use antibacterial treatments to stop the disease from spreading.

18. Ulcerative White Spot

Ulcerative White Spot disease causes small, ulcer-like lesions on the coral’s surface, leading to tissue death.

• Causes: Bacterial infections, often linked to poor water quality or injury to the coral.
• Symptoms: Small white spots or ulcers on the coral’s surface.
• Treatment: Improve water conditions and use antibacterial dips or treatments to control the disease.

19. Patchy Necrosis

Patchy Necrosis is a bacterial disease that causes irregular patches of dead tissue to appear on the coral’s surface, spreading rapidly in some cases.

• Causes: Bacterial infections, often related to environmental stress or injuries.
• Symptoms: Irregular patches of tissue loss on the coral’s surface.
• Treatment: Quarantine affected corals, improve water quality, and treat with antibacterial solutions.

20. Pests

Pests such as flatworms, nudibranchs, and Aiptasia anemones can also harm coral health by feeding on coral tissue or competing for resources.

• Common pests: Flatworms, nudibranchs, Aiptasia, red bugs.
• Symptoms: Coral bleaching, tissue loss, or stunted growth.
• Treatment: Use pest-specific treatments such as flatworm exit, nudibranch removal, or biological control like peppermint shrimp for Aiptasia.

Conclusion

Coral diseases and pests are a major challenge in both wild and aquarium environments. By monitoring your corals closely, maintaining stable water conditions, and taking immediate action when you spot symptoms, you can help prevent and treat these issues before they become widespread. Understanding these common diseases and pests is the first step toward ensuring a healthy and thriving reef system.