Place - The Sea - Coral Reefs

Facts -

The world's first coral reefs occurred about 500 million years ago, and the first close relatives of modern corals developed in southern Europe about 230 million years ago. By comparison, the Great Barrier Reef is relatively young at just 500,000 years old. The current reef's structure is much younger at less than around 8,000 years old.

What Is A Coral?

Despite the fact that corals look more like rocks or plants, they are definitely animals. Coral colonies are composed of many tiny, cup-shaped animals called polyps, which are related to jellyfish. A single coral polyp may be as large as a saucer or smaller than the head of a pin. Millions of polyps working together in a cooperative colony generation after generation create the limestone skeletons that form the framework of the beautiful coral reef.

How Do Corals Start Out Life?

Corals begin life in tropical waters as free-floating larvae. After a relatively short period of time, the larva eventually attaches itself to a hard surface and becomes a polyp. Polyps divide asexually and form colonies. Coral colonies reproduce both sexually and asexually. In sexual reproduction, the coral polyps release both eggs and sperm into the water. (This is also known as coral spawning.) One type of asexual reproduction occurs when fragments of coral are broken off as a result of storm action. The broken pieces of corals usually survive and continue to grow and produce a new colony. This process is referred to as “fragmentation”.

What Do Corals Eat?

A coral polyp consists primarily of tentacles, a mouth and a gut (think upside down jellyfish). Many corals are passive feeders on plankton. Most corals also get nutrition from microscopic algae (zooxanthellae) living within their tissue. Coral polyps are generally nocturnal feeders and are provided sugars made by their photosynthetic zooxanthellae during the day.
Top of Page

Where Does The Framework Of A Coral Reef Come From?

Corals extract calcium and carbonate from seawater to build an inner skeleton that is external to the coral. This external skeleton lies underneath a thin layer of tissue. Over the years millions of coral polyps in colonies create the framework of the coral reef. Coral reefs grow very slowly. It may take up to a hundred years for a coral reef to grow one meter (around three feet).

What Is The Largest Coral Reef In The World?

As the name implies, the Great Barrier Reef, located off Australia’s East Coast is the largest coral reef in the world. This enormous reef is over 2023 kilometers (1257 miles) long and covers more than 300,000 square kilometers (about 186,000 miles). Home to more than 1500 species of fish, dolphins, whales and sea turtles, the Great Barrier Reef is actually a collection of more than 3000 smaller reefs. The second largest reef lies off the coast of Belize, in Central America.

Coral reefs are among the most biologically diverse ecosystems on earth. Second only to tropical rain forests in the number of species they harbor, they are sometimes called the “rainforests of the sea”. Although coral reefs only occupy about 0.07 percent of the ocean floor (an area roughly the size of Texas), they are home to as many as one quarter of the world’s marine species. Coral reefs offer important income sources for their human neighbors through tourism and fishing, which provide both subsistence and trade. Recently, scientists have begun to discover that coral communities may contain valuable medicines that may one day lead to treatments for cancer and HIV. For coastal communities, coral reefs also play an important role in protecting their coastlines from storms.