marine biome built from calcium carbonate skeletons secreted by coral polyps
the rainforest of the sea: hosts 25% of all marine species on less than 1% of ocean floor
symbiosis between coral and zooxanthellae algae drives reef productivity through photosynthesis
three types: fringing, barrier, and atoll (formed around subsiding volcanoic islands)
Great Barrier Reef is the largest living structure visible from space
reef growth requires warm, clear, shallow water with specific climate zone conditions
threatened by ocean warming (bleaching), acidification (from carbon cycle disruption), and pollution
provides coastal protection, fisheries, tourism, and pharmaceutical compounds
evolution of scleractinian corals spans 240 million years
recovery from bleaching events takes decades if conditions stabilize
essential for marine ecology and the livelihoods of 500 million people