What is a Coral Reef?

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  • Written By: Diana Bocco
  • Edited By: Bronwyn Harris
  • Last Modified Date: 01 October 2019
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A coral reef is a sea structure made out of living organisms that form a wall together. Stony corals are usually the main organism found in a reef, but other types of skeletal material also join together to form the thick walls. It is also "constructed" by the thousands of fish, sponges, and sea urchins grazing around the area. As these organisms move about, they actually help the reef settle and gain a more stable structure. Waves are also partly responsible for the wall's size and format, as they affect the geology of the formation.

This living structure is very effective at absorbing nutrients from the waters surrounding it. This includes obtaining phosphorus and nitrogen from sea waters, and other nutrients from small organisms making their home in it. A coral reef is one of the largest living communities in the world. Thousands of species make their home there, including over 4,000 different tropical fishes, jellyfish, crabs, sea urchins, and starfish. Mammals may visit, but none actually live on or near it.

91.9 percent of the world's coral reef mass is situated in the Indo-Pacific region, with Australia taking a major percentage of that. There are basically none of these structures on the American west coast or on upper Asia, including Russia. This is mainly due to cold waters, but also to the effect of powerful water currents in the area.


Humans are the biggest threat to the integrity of a coral reef. Because of pollution, boat traffic, and aggressive fishing, reefs are now considered in danger and are protected under the Great Barrier Reef Marine Park Authority, an Australia-based institution. The illegal trade on saltwater aquarium fish is also a major factor on their destruction, as little can be done to stop collectors from around the world to request exotic, pricey species.

A coral reef is also susceptible to major environmental changes, including global warming, which affects water currents and marine migration. Coral bleaching, a form of erosion, occurs when water temperatures reach higher-than-normal levels. This can prove disastrous for a reef.


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Post 3

@ Parmnparsley and Amphibious54 - The biggest immediate threat to the Florida Barrier Reef system is the ongoing oil spill in the Gulf of Mexico. The Deepwater Horizon Oil Spill perpetuated by failures in BP's, Halliburton's, and Transocean's processes to safely drill for oil has the potential to completely destroy, as Amphibious54 stated, the world's third largest barrier reef system.

Coral reefs are actually created through a process that relies on the symbiotic relationship between coral polyps and zooxanthellae algae. This makes corals hypersensitive to anything that affects the oxygen content, temperature, bacterial formation, and light saturation of the water. The oil from the Deepwater spill has the potential to affect all of the above; essentially suffocating the reef, and destroying thousands of years of reef building. This is something that money cannot fix.

Post 2

There is not much difference between barrier reefs and coral reefs. Coral reefs are any type of reef that is formed by the calcium carbonate deposits of coral polyps. Barrier reefs are reefs that form a protective barrier to a land mass. Barrier reefs usually run parallel to a nearby land mass and form protective lagoons. Barrier reefs are important because they create the protective spawning grounds for fish and create one of the oceans largest ecosystems. The reefs at Dry Tortuga are actually part of a barrier reef system that runs along the Florida Keys; creating the world's third largest Barrier reef next to the Great Barrier Reef, and the Belizian Barrier Reef.

Post 1

What is the difference between a barrier coral reef and a coral reef? Is one more ecologically important than another? I once went to the Dry Tortugas national park in the Florida Keys and saw the reefs there. They were Amazing! I would hate to see these reefs destroyed, but I always hear about things like coral bleaching, and hurricane damage to coral reefs What are some of the biggest challenges in protecting Florida's reefs?

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