Are Corals - Minerals, Plants or Animals?

It’s a mineral, a plant, and an animal! Here's How:

A coral reef is a colony for millions of tiny creatures called polyps. When they grow, each poly develops a hard, limestone skeleton on which the next generation polyps grow.

Coral polyps close up during the day, during night the reefs comes to life when the corals extend their tentacles into the water to trap the prey. Coral reefs cover 619,000 square kilometer of Earth’s surface. 

Types of Coral Reefs

The three types of coral reefs are

1. Fringing reefs – Grows along seashores

2. Atolls – Grows around volcanoes which have not erupted for years

3. Cay – is an island completely made of corals

How to grow a tropical coral reef? 

1. Choose a sea which is free from pollutants.

2. Check the depth of the sea, a reef won’t grow below the depth of 98ft because there’s not enough sunlight.

3. The temperature of the water must not be colder than 21 degree and warmer than 30 degree Celsius.

4. The nutrient content should be moderate to less otherwise there will be rich growth of algae which could suffocate the coral reef. 

Timeline of Coral Reefs

500 million years ago – The world’s 1^st coral reef appeared

230 million years ago – Modern corals 1^st developed in the early Triassic era

199 million years ago – At the end of the Triassic era, two third of the coral types were wiped out by a climate change

18 million years ago – The formation of Australia’s barrier reef begins but its growth started and stopped several times

18,000 million years ago – Temperature on earth falls and sea water becomes trapped as ice in enormous glaciers, causing sea levels to fall to their lowest levels ever. Any coral reefs exposed during this period dies. 

10,000 to 8,000 years ago – The reef we can see today begins to develop at the end of the last great ice age. Melting of glaciers increases the level of sea.

Why do we need Reefs on earth? 

An estimated 500 million people depend on coral reefs for their food or livelihoods.

The carbon dioxide in water is converted into limestone by coral reef.

Certain medicines are made using the chemical compound of the reef.

Without coral the water would rise, destroying precious habitat.

It acts as a natural barrier that prevents the strong waves and tides from coming ashore. 

Different Shapes and Sizes of Reefs

Brain coral:

It has a giant brain like structure due to the wrinkled edges.

Fan coral:

A large lacy skeleton, formed by linkage of polyps of fan coral

Dead Mans Fingers:

The tentacle of these polyps looks like decomposing fingers 

Staghorn Coral:

This reef grows at a high speed, which resembles antlers.

Great Reefs of the World

1. The Great Barrier Reef, Australia

One of the largest living structures on the earth formed by the combination of 3,000 reefs which covers an area more than 2010 kilometer. 

2. Kwajalein, Marshall Island

The world’s largest atoll that surrounds a lagoon 97 kilometer long.

3. Lighthouse reef, Belize

At the center of this Caribbean atoll lies the Great Blue Hole, 145 meter deep.

Threats to Coral Reefs 

1. Global Warming 

Increase in the temperature rises the ocean level which leads to the death of algae in the coral reef. 

2. Rising Seas

Global warming increases the level of sea which will have a dramatic effect on coral reef.

3. Pollution 

Reefs are damaged by the pollution of mining, fertilizers, oil spills and pesticides. 

4. Aquarium Trade 

Some fishermen in Indonesia and Philippines use cyanide poison to attract fish, that they then use to decorate their museums. 

Written By - V. Mary Adhasha

Edited By - Tushna Choksey