Coral reefs..

Coral reefs are a group of coral animals that are symbiotic with algal plant species...

Coral reefs generally live on the beach or areas that are still exposed to sunlight or about 50 meters below sea level.
Some types of coral reefs can live deep in the sea and do not require light, but this coral reefs are not symbiotic with algae and do not form corals.

Coral reef ecosystems are predominantly in tropical waters, coral reefs are very sensitive to changes in their environment, especially temperature, salinity, sedimentation, and it also requires the quality of natural waters. Similarly, the change in environmental temperature due to global warming that hit tropical waters a few years ago has led to coral bleaching followed by mass deaths of 90 to 95 percent..

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