Why are corals called the rainforest of the ocean?

Chasing CoralFeb 26, 2022

Coral reefs are often called the "tropical rainforests of the sea" for their astounding richness of life. ... Corals are tiny animals that live in colonies and derive nourishment and energy from a symbiotic relationship with zooxanthellae algae.

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Why are corals called the rainforest of the ocean?