Would you ever mistake a coral for a jellyfish? Probably not. Yet corals are related to jellies, as well as to other invertebrates such as sea anemones and sea pens.
There are thousands of varieties of coral and one of the most recognizable is the stony, or reef-building, coral. Like all corals, these comprise thousands of tiny marine animals that live in colonies. When the animals die, they leave behind their hard skeletons, which become building blocks for new corals to attach to. As time goes by, this accretion of animals and their skeletons form reefs—some as small as a rock, others as big as the Great Barrier Reef.
Reef-building corals share some characteristics with plants—for example, they need direct light to grow. Corals thrive because of their symbiotic relationship with specialized photosynthetic algae called zooxanthellae that live within their tissue. Like rain forests, which house approximately 50% of the world’s terrestrial species, coral reefs are vital to the ecosystem, providing habitat to 25% of all marine species—including fish, mollusks, worms, crustaceans and sponges, to name just a few. Yet they occupy less than 0.1% of the ocean’s real estate.
Like the rain forest, corals are a fragile ecosystem. Corals are particularly susceptible to even the most moderate changes in their environment. Storms can break the colonies apart; pollution can dissolve the calcium carbonate structures; a few degrees change in temperature can kill the animals entirely. When a reef is in danger, the entire chain of life that depends on it is imperiled, as well.
For these reasons, collecting coral from the wild is carefully regulated. In fact, the Seattle Aquarium doesn’t collect coral at all—the majority of the reef-building corals we have here have lived in a captive environment for a very long time and much of what you’ll see in our exhibits we’ve grown ourselves.
Coral forms an important part of our Pacific Coral Reef exhibit—not only because it’s beautiful to look at, but because it is a cornerstone of the tropical ecosystem and gives us an opportunity to educate visitors about the interconnectedness of marine life, from the tiniest polyp on a reef to the vast array of marine animals, large and small, whose lives depend on its continued health.
You can find more information about the various types of corals in the Winter Fishtival: Coral Reef Fun Facts blog post.