31 - Coral reef disappearance
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1Cause
Coral is a symbiosis between colonies of polyps and photosynthetic algae, zooxanthellae, which give coral its beautiful color.
If the water temperature increases (due to climate change), the coral expels its micro-algae (the symbiosis is broken). Depigmented, it reveals its white skeleton.
If this continues, the coral dies, and filamentous algae covers its skeleton.
At +1.5°C, 70 to 90% of corals disappear At +2°C, more than 99% of corals disappear.
1Consequence
“We must consider here the yields of fishing. 25% of marine biodiversity depends on coral reefs. Fewer corals means fewer fisheries resources.”
2Other possible causes
Acidification alters the calcification processes which limit the development of corals, shelled animals and plankton which are at the base of the marine food chain. All marine biodiversity is thus threatened. For corals, the main cause of disappearance is not acidification but marine heat waves (climate change)
It is mainly marine heat waves that kill corals. The “disappearance of corals” map can therefore be linked upstream by the participants to the “climate change” or “increase in climatic hazards” map, of which marine heat waves are a part.
1Other possible consequence
25% of marine biodiversity depends on coral reefs. Fewer corals mean fewer fisheries resources.