Coral reef

Coral reefs are some of the most diverse ecosystem in the world. Thousand of species rely on the reefs for survival. Thousand of communities all over the world also depend on coral reef of food, protection and job A reef is a strip or ridge of rocks,sand or coral that rises to or near the surface of a body of water. The best known, reef are the coral reef development through biotic process dominated by coral and calcareous algae.


Corals are animals even through they may exhibit some of the characterstics of plants and often mistaken for rocks. Corals can exist as individual polyps or in colonies and communities that contain hundreds to hundreds of thousands of polyps .Corals are found throughout the oceans from deep, cold waters to shallow, tropical waters.


Most reef building coral contain polysynthetic algae called zooxanthellae that live in their tissues. The Coral and algae have Mutualistic relationships Coral provide the algae with protected environment and compounds they need for photosynthesis. In return, the algae produce oxygen and help the coral to remove wastes.
Zooxanthellae supply the coral with glucose, glycerol and amino acid which are the product of photosynthesis. The coral uses this product to make for protein fat and carbohydrate and produce calcium carbonate. This is the driving force behind the growth and productivity of coral reefs.
Zooxanthellae also responsible for unique and beautiful colours of corals. When colours become physically stressed the polyps expel there algal cell and the colony take on a stark while appearance with is commonly known Coral bleaching. It continued for long this Coral bleaching may result into death of corals.

Coral formation

Coral reef begin to form when free swimming Coral larvae attached to submerged rocks or other hard surface along the edge of Island or continent. As the Coral grow and expend reefs take on one of the form of coral reefs.

Type of coral reefs.

Following are the three primary types of coral reef

Fringing Reef

Type of Coral Reefs It is the most common type, is projected seaward directly from the shore forming border along the shoreline and surrounding Island

Barrier Reef

They also border shoreline but at a greater distance. They are separated from thier adjacent land mass by a lagoon of open, often, deep water.


It is formed when fringing reefs is formed around a volcanic Island that subside completely below sea level while the coral continues to grow up ward. Atoll are usually circular for oval with a centrallagoon.

Condition required for growth of Coral Reefs

Following condition are required for growth of coral reefs
  1. Shallow coral reefs grow best in warm water (21-29 oC)
  2. Reef building coral prefer clear and shallow water where lots of sunlight filter through to their symbiotic algae. Mostly they occupy depth of 18 to 27 meters.
  3. Corals also need saltwater to survive so they also grow poorly near river opening with fresh water, run off.
  4. Availability of plankton which is taken up as food is also necessary for growth of coral reefs
Due to above factors Coral are mostly found in tropical waters e.g. Eastern coast of Africa, Southern coast of India and Srilanka, Red Sea , North East and north west Australia Florida Caribbean Island etc.

Threats to coral reefs

As per an estimate around 20% of world's reefs are damaged beyond recovery and about half of remaining is under constant risk collapsing. Some of major threats to coral reefs are.
  1. Climate change It is dangerous because of factor like increase in temperature, sea level rise etc may lead to death of corals.
  2. Unsustainable Fishing Tt will disturb the ocean ecosystem and therefore the supply of nutrients to coral reef will get impact
  3. Pollution Release of toxic element in sea is resulting into death of corals