Your Online Guide to the World of the Coral Reef

Coral Reef Biome

The coral reef biome is one of the most important and distinctive types of biomes to be found on Planet Earth.

Coral reefs provide us with many benefits, not the least of which are food resources, new medicines, and protection of island shores.

In terms of biodiversity, that of the coral reef is the richest of all marine biomes. Although accounting for only a tiny fraction of the total surface area of the sea, coral reefs are nonetheless home to nearly 25% of all known marine species.

Unfortunately, among all of the earth's marine biomes it is that of the coral reef that is the most threatned by the ever-expanding impacts of human activities.

WHAT IS A "BIOME"? - A BIOME is best defined as a major biological community-type that recurs over a broad geographic scale under a particular set of environmental conditions.

Geography of the Coral Reef Biome

Examples of the coral reef biome are mainly found in shallow tropical portions of the Western Pacific, Indian, and Atlantic Oceans.

geography of coral reef biome
Geography of the coral reef biome

These are the places on Earth most ideally suited for the settlement, growth, and survival of reef-building hard corals.

For more information on where coral reefs are found, visit our web page on coral reef distribution.

Dominant Species of the Coral Reef Biome

Coral reefs are home to thousands of different species of plants,fishes, and other coral reef animals, but the coral reef biome is dominated by just a few main groups.

These "dominant groups" include one type of unusual animals called the stony or Scleractinian corals, and a type of marine algae called crustose coralline red algae.

Stony (Scleractinian) Corals

Most of the accumulated calcium carbonate that forms the foundation of modern coral reefs is derived fromt the hard, protective skeletons of countless numbers of small individual coral animals called polyps.

But coral polyps do not lead solitary lives. Instead, they live as parts of large cohesive groups called coral colonies that generally exhibit one of three basic growth forms, called massive, branching, or plate-like (pictured below).

coral growth forms
Massive (left), branching (center) and plate-like (right) are the most common growth forms of scleractinian coral colonies.

Each coral colony is composed of a great number of genetically identical individuals. Within each colony, only the outermost layers are composed of living polyps. Succeeding generations are built upon the skeletal remains of their forbearers.

The exact shape, size, and color of these colonies are subject to modification by local environmental conditions such as wave action, currents, prevailing winds, etc., often leading to substantial variability in the appearance of colonies of the same species.

Occasionally isolated colonies may be found, but coral colonies typically grow in larger multi-species assemblages that we call coral reefs.

Crustose Coralline Algae (CCA)

Unlike terrestrial biomes - whose physical structure and complexity is primarily determined by large plants - large-scale aspects of the physical structure of the coral reef biome is largely determined by animals.

crustose coralline algae
Crustose coralline algae

Still, corals are not the only dominant species found in the coral reef biome.

One group of red algae (Phy. Rhodophyta) called the crustose coralline algae or "CCA" (Subclass Corallinophycidae) are ubiquitous on coral reefs, and play an important structural role in the formation of coral reefs.

Coral Reef Plants ►