A Walk on the Great Barrier Reef

In her nonfiction work, A Walk on the Great Barrier Reef (1988), award-winning children’s author Caroline Arnold describes the diverse lifeforms that make their homes in Australia’s unique Great Barrier Reef. Arnold has written more than 170 fiction and nonfiction books for children. A Walk on the Great Barrier Reef was listed as an Outstanding Science Trade Book by the Children’s Book Council and the National Science Teachers’ Association (CBC /NSTA). The book features full-color photographs by Arthur Arnold. Booklist praises A Walk on the Great Barrier Reef as a “photographer’s delight,” and School Library Journal calls the photographs “stunning.”

Arnold first describes the magnitude of the Great Barrier Reef. Extending in a chain for more than 1,200 miles along the northeast coast of Australia, the Great Barrier Reef is in the Coral Sea part of the Pacific Ocean. The longest coral reef in the world, the Great Barrier Reef is known as one of the world’s natural wonders. Arnold explains that a reef is essentially an underwater wall, the top of which sits just below the surface of the ocean. There are three different kinds of reefs: the fringing reef, the barrier reef, and the atoll. Barrier reefs, of which the Great Barrier Reef is an example, have a lagoon between the reef and the shore of an island or continent. Reefs can be formed of different things, such as sand, coral, and rocks. The Great Barrier Reef is a coral reef. Coral may look like a plant, but it is really a colony of tube-shaped animals called coral polyps. Coral reefs require warm, clean water for the coral to grow.

There are more than 350 kinds of coral on the Great Barrier Reef. Coral polyps have soft bodies, but hard skeletons for protection. Coral polyps are small, only 1 mm to 8 mm across. They feed by using their tentacles to pull zooplankton into their mouths. Arnold explains that coral colonies grow when coral polyps “bud” or produce new polyps, which make new skeletons. New colonies are formed when the corals produce planulae; tiny pear-shaped growths with small hairs that allow them to swim. The planulae attach to hard surfaces and use calcium carbonate to grow hard skeletons. Algae are tiny plants that live in the coral and help build the reef by making calcium carbonate deposits, giving the planulae a place to attach. There are many different kinds and colors of coral, including some that look like brains, and others that look like the undersides of mushrooms. Over time, waves grind the dead coral to sand, making a hard surface on the reef, and creating small islands called coral cays.



Arnold describes other creatures that live in the Great Barrier Reef, including the beautiful but dangerous sea anemone, which releases poison threads to paralyze its prey. The clownfish enjoys a symbiotic relationship with the sea anemone. A special coating on the fish’s body protects it from the anemone’s poison. The anemone offers the clownfish shelter from other predators, and the fish helps the anemone by protecting and cleaning it. Giant anemones can grow to be 3 feet across.

Sea stars, or starfish, are echinoderms that also live in the Great Barrier Reef. They can have between 4 and 50 arms. They use tube-like feet to move and push their stomachs out of their mouths to eat their food. The poisonous crown-of-thorns sea star is a threat to the reef. It feeds on coral polyps and has nearly destroyed sections of the Great Barrier Reef. Arnold details other reef inhabitants: brittle stars and serpent stars, sea cucumbers, and crabs. Sea worms also live in the Great Barrier Reef. They are known as “magic carpet worms” for their bright colors. Octopus, sea hares, and clams are other diverse forms of life found in the Great Barrier Reef.

Many kinds of fish also inhabit the Great Barrier Reef, but Arnold advises that one must snorkel or dive to see them. They include grouper, zebrafish, the square-shaped boxfish, and sharks. On summer nights, Arnold explains, one might see a giant green sea turtle. The female green sea turtle returns to the same island, or coral cay, every year to lay her eggs. She digs a hole in the sandy beach and lays around 100 eggs, then covers them with sand. This is the only time the sea turtle comes ashore. Loggerhead and hawksbill turtles also lay their eggs in the sand. Coral cays in the Great Barrier Reef also provide food for migrating and nesting birds. Some coral cays, like Heron Island, have trees. These trees may have sprouted from seeds washed up on shore or dropped by visiting birds.



Arnold concludes with a warning: The Great Barrier Reef is in danger. People damage the Great Barrier Reef when they disturb its “delicate balance” of life. She notes that in 1979, the Australian government designated part of the Great Barrier Reef as a national park, helping to protect its wildlife.

Throughout A Walk on the Great Barrier Reef, scientific terms and other vocabulary words appear in bold print. These terms are defined in a glossary at the end of the book. A Walk on the Great Barrier Reef also features an index, diagrams, and maps. The book is a part of the acclaimed Carolrhoda Nature Watch series.