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Abiotic Factors

Abiotic factors are non living factors that influence ecosystems such as temperature, light and available nutrients.

Reef Around North West Island: courtesy of Great Barrier Reef Marine Park Authority

Temperature- Coral reefs thrive in water temperatures of 77° to 84° Fahrenheit ( 25° and 29° Celsius ). Certain corals have evolved to survive outside this temperature range such as ahermatypic corals. (see Adaptations and Relationships) The types of corals you find in the Great Barrier Reef are hermatypic corals- meaning they contain zooxanthellae algae and are colorful. These corals can survive in the reef's ranging water temperatures of 64 - 91° Fahrenheit (18-33° Celsius) 

Nutrients -  Corals survive only in clear  water, without much sediment, where light can breach the surface of the water.  Since there isn't much debris floating around, the water  is usually low in nutrients. These waters would not naturally have many animals living in them because of the lack of nutrients, but since corals live here, many thousands of animals survive by eating either  the coral, or the animals that eat the coral.

Light- Light is incredibly important for coral reefs.  The reason corals are able to survive in such non-nutritious  water is because of the zooxanthellae algae produces food for the coral as well as itself.  In order to photosynthesize to produce food however, the algae needs light.  Without light, this ecosystem cannot exist.

Wave Acton on Reef Crest: courtesy of Great Barrier Reef Marine Park Authority

Salinity- Corals tend to live in  salty water, surviving in a range of 27-40 parts per thousand (ppt) but preferring 36 ppt.

Depth- Corals live in shallow water and are usually found to a depth of 60 meters (197 feet) but ahermatypic corals go far deeper. 

Wave Motions-  Water movements help take away waste and bring food.