Often times when we think of coral we think of a multicolored paradise for many marine creatures. Coral actually gets its coloring from algae that feed the coral. The algae live inside the tissue of the coral essentially they share resources in a constantly changing environment. But what happens to change those terms?
Coral can only survive within a certain temperature. As ocean temperatures rise so too do the occurrences of coral bleaching. Algae also have a limited range of climate that can be tolerated. Ultimately coral cannot survive without algae.
Coral bleaching has grown substantially over the last 20 years. Coral has a symbiotic relationship with algae when external variances occur the algae often leaves the coral which then leads to bleaching. Corals vary in their response to heat and light stress. Additionally, bleaching does not always result in the death of the coral.
Zooxanthellae is a type of single-celled dinoflagellate algae. Scientists believe the primary cause of mass coral bleaching is increasing sea temperatures. Local instances of bleaching can be caused by disease, cyanide fishing, and sedimentation which comes from undersea activities like dredging, as well as changes in water salinity. Currently, 16% of the oceans coral is considered to be dead.
Not only corals are affected. giant clams and anemone also bleach in response to thermal stress. Some reefs are considered to be “resilient reefs” which can make a healthy recovery given the proper conditions.
Information on coral bleaching made available from The Nature Conservancy & NOAA