Waves

• Waves are some of the biggest threats to coral reefs because they cause erosion. Large waves can break the coral, shattering its fragments.
  
  

Storms

• Storms are a danger because they also can break off pieces of the colony. Although a storm generally does not kill an entire colony, it damages enough that by the time it would take to repair itself, algae overgrows the colony and kills it.
  
  

Low Tides

• Low tides expose the reefs, causing them to die from ultraviolet radiation.
  
  

Weather

• El Nino weather causes great harm to the reefs because the warm water, low salinity and water causes damage to the reef's physiology.
  
  

Predation

• Coral reefs are often eaten by fish and other sea life. These creatures eat the soft polyps of the coral. This can kill the entire colony.