Black Band Disease (BBD)

Why in news?

A recent study reveals that heat stress combined with a rare disease has wipe out 75% of Goniopora coral colonies on Great Barrier Reef.

Goniopora corals – Commonly known as flowerpot/daisy corals, are a genus of colonial stony corals found throughout the Indo-Pacific in lagoons and turbid water conditions.

• Black Band Disease – It is a severe, globally occurring coral disease characterized by a visible black, expanding band that degrades coral tissue, leading to tissue death and bare skeleton.
• Caused by – Consortium of microbes such as
  • Cyanobacteria (photosynthetic, toxin-producing).
  • Sulfate-reducing bacteria (SRB) (thrive in oxygen-free zones).
  • Sulfide-oxidizing bacteria (SOB) (use chemical energy).
• Together, they create toxic sulfides and anoxic conditions, leading to coral tissue death.
• Historical Context – 1^st reported by Antonius (1973) in Belize, Caribbean.
  • BBD is common in the Caribbean but historically rare in the southern Great Barrier Reef,
• It was distinguished from other coral diseases (white plague, white band) by its visible microbial biomass.
• Environmental triggers – The incidence of this disease is associated with sharp rises in sea surface temperature & nutrient pollution, driven by environmental stressors like ocean warming and contamination.
• Symptoms
  • Black Band Formation – A distinct, dark, tar-like band appears at the leading edge of the infection.
  • Tissue Degradation – The band moves across the coral, completely consuming the living tissue.
  • Exposed Skeleton – Behind the band, the white coral skeleton is left exposed.
• Treatment – The BBD is manually treated by removing the infected tissue and microbial mat.
• Prevention – Reducing stressors like pollution and addressing climate change to lower water temperatures are crucial for prevention.
• Impact
  • High virulence – BBD is a highly virulent disease that can rapidly kill coral colonies.
  • Widespread threat – It affects numerous coral species and reefs globally, impacting reef health.

References

1. Down to Earth | Black Band Disease (BBD)
2. Springer Link | Black Band Disease (BBD)