Coral Bleaching// Oceanography// wbslst// upper primary// kvs//nvs

Coral Bleaching

Definition

Coral bleaching is the whitening of coral colonies caused by the loss or expulsion of symbiotic zooxanthellae algae from coral tissues.

Without these algae, corals lose their major food source and eventually die if stressful conditions persist.

Process

Rise in sea surface temperature stresses corals.

Zooxanthellae leave the coral tissues.

Corals lose their natural colour.

White calcium carbonate skeleton becomes visible.

Prolonged bleaching leads to coral mortality.

Major Mass Bleaching Events

1982–83: Strong ENSO (El Niño) event caused extensive bleaching in the eastern Pacific.

1997–98: One of the most severe global bleaching events affecting reefs in the Indian, Pacific and Atlantic Oceans.

Causes of Coral Bleaching

Global Causes

1. Global warming
2. Increased sea surface temperature
3. El Niño–Southern Oscillation (ENSO)
4. Ocean acidification
5. Biological Causes
6. Disease outbreaks
7. Pathogenic infections

1. Local Causes

1. Marine pollution
2. Increased sedimentation
3. Oil spills
4. Coastal development
5. Mining activities
6. Overfishing
7. Destructive fishing practices

Effects

• Loss of zooxanthellae
• Decline in coral growth
• Reduced biodiversity
• Destruction of reef ecosystem
• Loss of fish habitat
• Economic loss to fisheries and tourism
• Coral mortality
• Coral Recovery
• Corals can recover if:
• Environmental stress is removed.
• Zooxanthellae recolonize coral tissues.
• Water temperature returns to normal.
• Human disturbances are minimized.
• Recovery may take 30–100 years, depending on the severity of damage and local environmental conditions.