Corals are a type of invertebrate, meaning they don’t have a backbone. There are thousands of different species of corals. Each coral consists of many tiny animals called polyps.

Corals can be categorized into two main types: soft and hard. Soft corals cannot build reefs, while hard corals, also known as stony corals, have tough structures and are responsible for creating reefs. Sadly, many hard corals that help build reefs are in danger. 

At the Columbus Zoo, we’re dedicated to coral conservation, specifically through participation in the Association of Zoos and Aquariums' (AZA) Saving Animals from Extinction (SAFE) program and the support of the Florida Reef Tract Rescue Project.

Scientific Name: Anthozoa

Conservation Status:

Size: Varies, depending on the species and whether they are reef-builders.

Weight: Varies, depending on the species and whether they are reef-builders.

Coral from reef tract rescue project
Nutrition
Corals mainly eat tiny animals called zooplankton and tiny bacteria called bacterioplankton that are floating in the water. They use their tentacles, which are part of their polyps, to catch this food.
Current Range and Historic Range
Corals are found in all oceans worldwide. However, reef-building corals are typically only found in tropical and subtropical waters. The global coverage of living coral in reefs has severely declined over the past several decades.
Habitat
Corals need saltwater to live and can be found in both shallow and deep areas. Reef-building corals usually thrive in shallow, clear waters where sunlight can penetrate. This light is important because it helps tiny algae called zooxanthellae, which live inside the corals, to perform photosynthesis. This process allows the corals to convert sunlight into energy, which is essential for their growth and survival.
Predators and Threats
Corals are an important food source for many animals, including some species of fish, sea stars, and sea slugs. 

One of the biggest dangers to corals is climate change. It leads to ocean acidification, which makes it hard for corals to grow and recover quickly from damage. Another issue is bleaching, which occurs when corals are stressed and eject tiny organisms called zooxanthellae. These organisms not only give corals their color but also help them get energy. Other threats to corals include pollution, overfishing, trash in the ocean, and human activities.
Physical Description and Adaptations
Calcium carbonate is really important for hard corals because they use it to build their skeletons. Each small coral animal, known as a polyp, produces calcium carbonate, which helps form its tough structure. As more polyps grow together, the coral reef becomes larger. In contrast, soft corals don’t produce calcium carbonate. Instead, they have flexible skeletons made of protein.
Reproduction
Corals can reproduce in two main ways: sexually and asexually. Most hard corals mainly reproduce through something called broadcast spawning. During this event, many corals in the same area release their eggs and sperm at the same time, allowing for fertilization. Some corals, however, use a method called brooding, where the baby coral larvae stay close to the parent and don’t travel far away.

Corals have two main techniques for asexual reproduction: budding and fragmentation. In budding, new corals grow out from the parent coral, while in fragmentation, a piece of the coral breaks off and can grow into a new colony.
Communication
Corals communicate by releasing chemical signals to attract fish and other organisms to reefs.
Behaviors
Broadcast spawning is one example of a fairly complex and remarkably timed behavior that some corals demonstrate to reproduce. During this process, many corals release their eggs and sperm into the water at the same time, showing a complex and well-timed behavior. In addition to spawning, corals can also display social behaviors and ways of feeding.