Coral reef communities are vital to ocean health.

Vibrant, colorful, a treat to the eyes—coral reefs are dubbed “rainforests of the sea” for good reason. Less than one percent of the ocean floor is covered by coral reefs but they are an essential environment for marine life. These reefs are an ecosystem housing a diverse species of fish eggs, developing larvae, and fish.

They may look like rocks, but corals are actually alive! Corals are animals that secrete calcium skeletons to form the complex reef structures we see. These animals, called polyps, belong to the invertebrate group Coelenterates. Also home to jellies and sea anemones, these organisms have a cylindrical soft body with an opening surrounded by tentacles. These tentacles have stinging cells that help the coral catch prey.

Not every type of coral forms reefs. Of the two main types of corals—hard and soft—hard corals have the ability to form calcium skeletons, and these are mainly reef-builders. Soft corals cannot build skeletal structures, but they are found along with hard corals. These corals look more like fans or brushes and have a feathery appearance. A coral reef has both these corals forming a varied community.

Hard corals (left) and soft fan corals (right). Photo credit: NOAA.

Corals themselves are translucent, but some of their flamboyant colors are due to algae called zooxanthellae, which co-exist with the corals symbiotically. These algae produce food for the corals and in return, receive nutrients and protection from them. Thus, coral is a combination of animal, vegetable, and mineral.

Most corals are found in the shallow tropical waters near the equator, as the algae need sunlight to produce food. But there are deep-sea corals widely distributed in the waters of the United States, Canada, Japan, Norway, and New Zealand. Some of the deep sea corals in the Northeast Canyons and Seamounts Marine National Monument are hundreds of years old—older than the California redwood trees. Deep sea corals do not require sunlight, instead, they get their nutrients by trapping organisms floating in passing water currents.

deep sea corals in northeast coral canyons and seamounts marine national monument
Deep sea corals in Northeast Canyons and Seamounts Marine National Monument.

The Corals at the New England Aquarium

Here at the New England Aquarium, our exhibits feature live corals as well as artificial ones. Search for Nemo in the Living Corals exhibit in our Tropical Gallery on the first floor or head to the top of the Giant Ocean Tank and explore the Yawkey Coral Reef Center. Press your face to the glass and experience the floor-to-ceiling immersion  of our newest exhibit: the Indo-Pacific Coral Reef

Photo/Reba Saldanha New England Aquarium The Tide event April 11, 2019
Indo-Pacific Coral Reef. Photo/Reba Saldanha.

Corals require lots of care and maintenance to thrive in aquarium tanks. They require light, a steady flow of Calcium-enriched water, and a safe space to grow. Aquarists work hard to make sure that the fish placed in the tanks don’t eat the coral polyps. Corals also compete with each other for food and space—they are territorial. So, they need to be constantly kept in check to see if the corals are “getting along well,” said Sarah Tempesta an aquarist in the Tropical Gallery.

“Coral will actually fight with each other. So, I keep tabs and make sure that one coral is not overgrowing the other,” said Sarah.

xenia living coral
Xenia in the "Living Corals" Exhibit.

When you think of the Aquarium’s coral reef communities, you probably think about our four-story Giant Ocean Tank and its Caribbean reef habitat, or our 9,000-gallon Indo-Pacific coral reef community. Both of these exhibits feature artificial corals as a backdrop for hundreds of fishes. Artificial corals require less maintenance. These corals are made mostly from polyurethane or rubber. The ingredients are animal-safe and sourced from manufacturers who specifically design these for aquariums and zoos.

Aquarium artists, Peter Brady, and Cailigh MacDonald refer to live coral pictures and mold the artificial ones similarly. “We try our best to make it look as close to the real coral as possible,” said Cailigh. 

Behind the Scenes: Making an Artificial Reef

The recently-unveiled aquarium exhibit, the Indo-Pacific Coral Reef, houses their handiwork at replicating an entire reef system. The floor-to-ceiling exhibit display a vibrant community of fishes and corals existing together, similar to the real ones on the tropical ocean floor. The handmade corals are cleaned regularly using animal-safe cleaning supplies. They are durable and long-lasting.

Conservation Context

Warming temperatures due to climate change, pollutant-dumping into oceans causing acidification—all affect coral reefs severely. Warm water stresses the corals making them lose their algae, in turn losing all color—a process called coral bleaching. Bleached corals are even more vulnerable to external stresses. Bleached reefs remain vulnerable and often die.
Corals take hundreds of years to grow into reefs. The Great Barrier Reef of Australia has corals that are almost 8,000 years old! These ancient animals have inhabited the oceans long before humans evolved, but due to the impacts of human-caused climate change and pollution, the future of these reefs is in jeopardy. The best chance for corals to revive right now is to slow climate change and reduce human-caused stresses on the oceans.

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