Reef-building corals cannot tolerate water temperatures below 18 c. optimal growth for these corals is in water between 23 c and 29 c, but some can tolerate temperatures as high as 40 c for short periods. most also require very salty water ranging from 32 to 42 parts per thousand, which must also be clear so that a maximum amount of light penetrates it.
climate change appears to be a major threat to the survival of reef-building coral. mass coral bleaching events and infectious disease outbreaks are becoming more frequent. several events might push ocean environments out of the temperature tolerance zones for reef-building corals. they include all but one of the events described below.
a) altered ocean circulation patterns and currents change temperatures throughout the global ocean.
b) global warming causes ice melting, which in turn dilutes the salt concentrations of the global ocean.
c) global climate change causes thermal stress as surface water temperatures in the oceans continue to rise.
d) thermal pollution of coastal waters due to the use of water as a coolant by power plants and industrial manufacturers.