Coral Reefs

These solid, geological coral structures are found in warm, shallow waters of the ocean, especially the tropics. They are formed from the remains of plants and animals and are subject to oceanographic conditions and fluctuations.

Each coral is comprised of the skeletal deposits from tiny marine animals or polyps. These polyps leave stony deposits behind when they die which form a solid, branch-like structure or coral reef.

Coral reefs provide a home to numerous species of marine life which include jellyfish, anemones, sponges, turtles, crabs, shrimps, sharks and molluscs. They are also living quarters for many types of plants such as algae, mangrove and sea grasses.   

Types of coral reef

There are three types of coral reef which include:

  • Barrier reef
  • Fringing reef
  • Coral Atoll

Barrier reef

This type often runs in parallel to coastlines but is usually divided from the land by means of a lagoon. This reef forms a barrier between the lagoon and the sea which is problematic for navigation purposes. 

One example of a barrier reef is the Great Barrier Reef which lies just off the North East coast of Australia. This is the largest coral reef in the world.

Fringing reef

This reef develops close to the shoreline, often extending back towards the beach. It is similar to the barrier reef except that this reef has shallower lagoons in the back reef, close to the shoreline.

A barrier reef has several deep sections within the lagoon.

Fringing reefs are found in the Red Sea and the Caribbean.

Coral atoll

This is the name given to concentric circles of coral which form on top of dormant volcanoes in the ocean. This type of reef starts life as a fringe reef around a volcanic island but continues to grow even as the volcano collapses. This leaves the reef as the only remaining structure.

Threats to coral reefs

Coral reefs act as ecosystems for fisheries, tourism and coastline protection. They are fragile structures which face a growing threat from climate change, excess algae production, water pollution and off-coastal dredging.

Hawaii coral reef research

A research project was initiated in Hawaii in 1998 to foster a greater understanding and awareness of the threats facing reefs surrounding the islands of Hawaii. This includes monitoring the processes which impact upon the functioning and wellbeing of the reef as well as searching for new ways to protect it.

Coral reefs are affected by natural changes in the ecosystem but are also subject to man-made stresses. In other situations they are threatened by natural changes which have been exacerbated by human intervention. 

For more information visit the Hawaiian Coral Reef Initiative site.