Coral reefs are built by mixotrophs, animals that are also plants. Corals are not only neither autotroph nor heterotroph, they are also neither female nor male. They provide habitat for over a quarter of the world’s fish species including the colorful ecosystem engineers that are parrotfish. Another notable group of ecosystem engineers inhabiting coral reefs are sea cucumbers. And humans also depend on them in various ways. Protected areas play a key role in conserving coral reefs, but diseases, eutrophication, ocean acidification and ocean warming remain a looming threat. But corals are not the only reef builders under threat. There are also shellfish reefs which fulfill similar ecosystem services.

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