Lemon Drop Damsel in Yellow (Black) Coral

A Lemon Drop Damsel (Pomacentrus moluccensis) in Black Coral (Order Antipatharia)

This small Lemon Drop Damsel found a pleasant, color-coordinated home amidst the branches of a black coral.

Black corals are found in all the world's oceans, but are most common in tropical and subtropical waters, and at depths below 50 m (164 feet), although they can be found at thousands of feet. Unlike most corals, they do not host symbiotic photosynthesizing zooxanthellae, the photosynthesizing algae that contribute to coral nutrition. Because they don't rely on that side gig, they can live at depths where sunlight is absent. They depend on capturing passing plankton and other lifeforms. In the Sea of Cortez, upwelling brings a lot of deep-water nutrients to shallow waters, and black corals live at diveable depths of 20 m (66 ft).

Black corals usually aren't black, when encountered underwater. They take their name from the color of their skeletons, the branching structures that hold up the individual polyps. Each branch in the image above contains many polyps, striving for food with their yellow tentacles. Skeletons of black coral are made of protein and chitin, a tough natural polymer that makes up the shells of insects. Most corals seen by divers and snorkelers have skeletons made of calcium carbonate, also the main component of seashells and limestone.

The damselfish does look like a delicious lemon drop. It's about the size of my thumb. Damselfish live primarily in tropical and subtropical waters; coral reefs hold many species. Garibaldi are the largest species of damselfish; they are common in the kelp forests of Southern California, although lately they've been found as far north as Monterey. Perhaps as the planet warms, black coral and lemon-drop damsels will appear off the California coast.