Reef Ecosystem

Coral reefs are built by scleractinian (stony) corals secreting calcium carbonate skeletons in symbiosis with zooxanthellae algae that provide up to 90% of the coral's energy through photosynthesis. This relationship makes reefs extremely sensitive to water temperature — above 1–2 °C above normal summer maximums triggers bleaching (zooxanthellae expulsion) and potentially coral death. Reef fish show extreme trophic and spatial specialization: cleaner wrasses operate mutualistic cleaning stations; surgeonfish graze algae preventing reef overgrowth; groupers are apex predators structuring community composition. Bleaching events since the 1980s have degraded over half of the world's reefs.