CORAL REEF

What is a coral reef?

A coral reef is a community of living organisms. It is made up of plants, fish, and many other creatures. Coral reefs are some of the most diverse ecosystems in the world. They are home to about 25% of all marine life!

There are sponges, sea slugs, oysters, clams, crabs, shrimp, sea worms, starfish and sea urchins, jellyfish and sea anemones; various types of fungi, sea turtles, and many species of fish. Think of them as the “rainforests of the oceans.”

Coral reefs have been around for millions of years. Less than 0.1% of the world’s ocean floor is covered by coral reefs. The reefs grow best in warm, shallow, clear, sunny and moving water. However, they grow very slowly—anywhere from 0.3 cm to 10 cm per year. The reefs we see today have been growing over the past 5 000 to 10 000 years.

Coral reefs are made of tiny animals called “polyps” that stay fixed in one place and are the main structure of a reef. Polyps have a hard outer skeleton made of calcium (similar to a snail’s shell).

Each polyp is connected by living tissue to form a community. Only the top layer of a coral reef contains living polyps. As new layers of the coral reef are built, the polyps leave the lower layers.

Each polyp has a ring of tentacles shaped like a cup around a central opening. The tentacles are like long arms with tips that can sting. They are used either for defense or to capture zooplankton (small animal life) for food.

The Great Barrier Reef is the largest coral reef. It is made up of over 2 900 individual reefs and 900 islands stretching for over 2 600 kilometers off the northeast coast of Australia.

Why are they important?

Coral reefs do a number of amazing things! Reefs

1. Protect shorelines from big waves by absorbing wave energy
2. Provide a safe place for fish to spawn (release eggs into the water)
3. Provide habitats for a large variety of organisms
4. Provide food (fish and shellfish) for many people living along coastlines
5. Are a source of medication—some anti-cancer drugs and painkillers come from reefs
6. Help in the carbon cycle
Are a good sign of ocean water quality: Healthy reefs = Healthy water.

Coral Reefs at Risk

Coral reefs are fragile ecosystems. They are very sensitive to any changes. Worldwide, coral reefs are disappearing for a number of reasons.