Coral Reef

Coral reefs are the most biodiverse marine habitat on Earth. Built by colonial cnidarian animals over millennia, they support thousands of fish species per reef - clownfish, angelfish, parrotfish, groupers, wrasses, and countless invertebrates. Reefs are climate-threatened: mass bleaching from warming waters has decimated the Great Barrier Reef and Caribbean reefs alike.

Zooxanthellae (photosynthetic algae) live in coral tissue - the foundation of the food web. Herbivorous fish (parrotfish, tangs) keep algae in check. Predatory fish (groupers, moray eels) top the pyramid. Cleaner fish/shrimp form iconic mutualisms.