Where are the major coastal regions and coral reefs?

In this chapter:

Coastal regions are places where the ocean meets the land
Coral reefs are found in shallow, often coastal waters
Coral reefs need very specific conditions to form
There are extensive coral reefs in many tropical waters
Not all tropical waters have coral reefs and not all coral reefs are in tropical waters

Introduction

Coastal regions are places where the ocean meets the land. Most people think of the coast as beaches but they are any place where dry land meets water, including cliffs and glaciers (as found in Antarctica). The coast also refers to land a little way off shore that is always covered with water. Since every continent is surrounded by water on most sides, coasts are found all over the world wherever the sea meets the land.

Coral reefs are found in shallow, often coastal waters. Coral reefs need very specific conditions to form. The water in a coral reef must stay above 20 degrees Celsius for most of the year. Any colder and coral polyps begin to die off after only a few days. Water also must be very clear and shallow, as coral polyps live in a symbiotic relationship (a mutually beneficial relationship between two organisms) with an algae that provides food through photosynthesis (the process by which plants make food from sunlight and carbon dioxide).

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There are three main kinds of coral reef. Fringing reefs are reefs that are found right next to the coast of a continent or island. Barrier reefs are found a bit further out from the shore, and there is a lagoon, or an area of deeper water, separating the reef from the land. The Great Barrier Reef, as you may have guessed from the name, is a barrier reef. Finally, atolls are reefs that are found in shallow water surrounding what many scientists believe are submerged extinct volcanoes that collapsed. Atolls are ring-shaped, sometimes including small islands and reef structures and have a lagoon in the middle.

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The conditions in these different kinds of reefs vary slightly - for example, tidal currents are stronger in fringing reefs than other reefs, and there are more endemic species (species only found in a certain place) in atolls.

There are extensive coral reefs around Indonesia, the Philippines, Papua New Guinea and northern Australia because conditions are favourable there. Warm ocean currents and shallow water allow coral to grow, creating some of the biggest coral reef systems in the world, including the Great Barrier Reef, which covers over 350 000 square kilometres of sea floor. Other extensive coral reef systems exist in the Caribbean Sea between North and South America and on the east coast of Africa. Not all tropical marine regions have coral reefs, however, and not all coral reefs are within the tropics. Due to cold ocean currents, places like western Africa and western South America have no coral reefs. Warm ocean currents have allowed coral reefs to develop in places like Southern Japan, south-western Australia and the Gulf of Mexico in North America.

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