Coral ReefsBy Seeley Phillips

What Is a Coral Reef?

Underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny animals found in marine waters that contain few nutrients.

Coral reefs form one of the most diverse ecosystems on this planet. They provide home for 25 percent of all marine species.

Where Can I Find Coral Reefs?

• They are most commonly found at shallow depths in tropical waters, but deep water and cold water corals also exist on smaller scales in other areas.

How Does a Reef Form?

• Coral reefs begin to form when free-swimming coral larvae attach to submerged rocks or other hard surfaces along the edges of islands or continents.

What is the Importance of Coral Reefs?

Coral reefs support more species per unit area than any other marine environment, including about 4,000 species of fish, 800 species of hard corals and hundreds of other species. This biodiversity is considered key to finding new medicines for the 21st century. Many drugs are now being developed from coral reef animals and plants as possible cures for cancer, arthritis, human bacterial infections, viruses, and other diseases.

Behavior and Diet

The polyps of a coral reef extend their tentacles at night to sting and ingest tiny organisms called plankton and other small creatures. Reefs only occur in shallow areas that are reachable by sunlight because of the relationship between coral and algae. Various types of microscopic algae, known as Symbiodinium, live inside of the coral, providing them with food and helping them to grow faster.

Coral reefs are found all around the world in tropical and subtropical oceans. They are usually found in shallow areas at a depth of less than 150 feet. However, some coral reefs extend even deeper, up to about 450 feet deep. Despite how important coral reefs are to life in the ocean, all of them in the world add up to less than one percent of the sea floor – an area about the size of France.

Reefs at Risk

There are a number of things damaging precious coral reefs:

• Fertilizer used on farms or home gardens washes into the oceans. The fertilizer creates conditions that make algae increase. The extra algae cover the coral and it dies.

• As CO2 emissions increase, more CO2 is absorbed into the oceans. This makes the water more acidic which makes it harder for coral to make their shells.

• Increased greenhouse gas emissions are making the water warmer. Coral can’t live in water that is too much warmer or colder than 26–27 degrees Celsius.

• Chemicals from sunscreen, pollution from sewage, and herbicides and pesticides used in farms or home gardens can all wash into oceans and poison coral.

• Dangerous fishing methods, like cyanide or blast fishing, harm and kill coral.

Why are Reefs Important?

They:• Protect shorelines from big waves by absorbing wave

energy • Provide a safe place for fish to spawn (release eggs into

the water) • Provide habitats for a large variety of organisms • Provide food (fish and shellfish) for many people living

along coastlines • Are a source of medication—some anti-cancer drugs and

painkillers come from reefs • Help in the carbon cycle • Are a good sign of ocean water quality: Healthy reefs =

Healthy water.