What causes coral bleaching?

Coral bleaching can be caused by a variety of factors including:

• Water temperature changes (usually over-heating)
• Too much sunlight, PAR or UV light
• Water chemistry changes (especially acidification)
• Excess silt
• Starvation due to insufficient prey caught from the water
• Bacterial infection
• Low tide and exposure to air
• Changes in salinity

Once coral has bleached, though it can recover, it is likely to be a struggle and have significant impact on the coral’s health. All the time that it has no zooxanthellae, it is probably struggling to find sufficient food and a downward spiral can begin, resulting in the death of the coral. These factors are all reasonably easy to control in an aquarium set-up, but globally corals are suffering, particularly due to increased temperatures and acidification of the sea. Some suggest that in as little as 50 years’ time the sea may be unable to sustain corals.

Written by Lizzi - Sparshot College - www.sparsholt.ac.uk