What Is Coral?

Contrary to popular belief, coral are animals not plants.  There are over two thousand different types of coral, which form colonies that play a key role in marine environments. Coral is made up of thousands of tiny organisms called polyps, that have soft bodies and a hard foot called a calicle. They have tentacle like arms that are used to gather their food. This a stationary organism, and live on a skeleton of calcium carbonate. Coral itself come in a variety of forms. Some can be hard and sharp, and some can be soft. The sizes and colors range and each species has different unique features.

Screen Shot 2017-02-27 at 11.01.23 PM.png“Coral Reef” by Pixabay under CC by 2.0


Coral Polyp” by Wikimedia Commons under CC by 2.0

Coral Reefs

In time, polyps continue to grow and die, which produces the foundation of a coral reef. The reefs are “the largest structure of biological origin on earth.”


Protection: Functions as a form of protection of the shores from harsh waves and storms

Habitat: Thousands of marine life call the coral reef home and it provides shelter and safety to these organisms.

Nutrients: Marine life lives off of nutrients produced by the reefs. Carbon and nitrogen fixing is an important part of the marine food chain. Nutrient recycling takes place and provides a very efficient system in this habitat.

Screen Shot 2017-02-27 at 11.12.14 PM.png

Benthic Life” by Wikipedia under CC BY 2.0

So how are these structures formed?

Coral reefs are formed by the production of CaCO3 and limestone, along with the breakdown of skeletal remains from coral and benthic organisms. The coral polyps secrete calcium carbonate. Polys survive by having an endosymbiosis relationship with zooxanthellae. Other organisms like seaweed, algae and sponges contribute to the production of the coral reef.

The relationship:

  • The Zooxanthella provides nutrients to the coral from photosynthesis
  • The coral provides protection and shelter to the Zooxanthellae because it lives within its tissue

Why are reefs important?

Coral reefs support more marine life per unit area then any other marine environment. There are so many different species and such biodiversity that it can lead to production and development of new drugs. Reefs provide economic and environmental services such as tourism, fishing and diving tours, and a large field for research and development.

Coral Reef Ecosystem

All the aspects of the coral reef act together in a unit called an ecosystem. This is a very high functioning ecosystem and is home to thousands of marine life. All the organisms contribute, but one of the most important parts of the ecosystem is the mangroves and sea grass.

Mangrove– Provides protection by stabilizing the shore line. Also helps produce nutrients and filters out pollutants. The roots of the mangrove serves as breeding and feeding grounds or marine organisms such as fish, invertebrates and others.

Sea Grass Provides nutrients to organisms such as sea turtles, sea urchins and thousands of others. Sea grass also provides protection and shelter for crustations like crabs and lobsters, and snappers. Functions as a filter to the water column, and release oxygen necessary for most marine life. Also the sea grass prevents sea bed erosion.


Acropora latistella”  by  Wikimedia Commons under CC by 2.0

Everything leads to the ocean, so the land is also an important part of the coral reef ecosystem. Pollutants, litter, and waste are detrimental to marine life because they end up getting into the ocean. Storm drains, streams, waste water, and litter on the beach ends up in these organisms habitat and have a large effect on their lives. Plastic being a large hazard to the organisms because it cannot be digested and essentially sits in their gut. Also evidence of suffocation of marine life like turtles, that get plastic wrapped around their necks.

Screen Shot 2017-02-27 at 11.26.27 PM.png

Stop trashing my oceans” by flickr under CC by 2.0

Mesophotic coral ecosystems (MCEs), is a common type of ecosystem that is home to light-dependent life, such as zooxanthellae corals. MCEs are typically at depths of 30-40 m and can extend over 150 m in tropical and subtropical regions.

Roles of Marine Organisms

The biotic component of the marine ecosystem has three main groups called producers, consumers, and decomposes. The organisms in these groups all play a key roll in making a functioning ecosystem.

Producers– These are autotrophic organisms which make their food through photosynthesis. Green plants, algae, and chemo-synthetic bacteria are all examples of producers in a marine habitat.

Consumers– These organisms obtain food from other organisms or organic matter and are animals, zooplankton, and heterotrophs. Consumers are broken down into primary, secondary, tertiary, and quatenary categories Primary feed on the producers and are herbivores. These organisms are sea turtles, zooplankton, and sea urchins. The secondary level feed on the primary producers and are organisms like raysand fish. The last levels are tertiary and quatenary, which feed on the secondary consumers and are the large fish, sharks, and sea lions.

Decomposers– Feed on dead organic matter. Crustations like crabs and lobsters are examples of decomposers. Also bacteria and fungi decompose dead matter and turn it into energy by releasing nitrogen, phosphates, and carbon back into their habitat.

Why should we care about these organisms?

There are many reasons why we need to care and protect these organisms. The coral reef and all the marine life surrounding it regulates important nutrients for both themselves and us as humans. Oceans and animals generate about half of the oxygen that people breathe. Also nutrients from corals and other organisms is a source of medicine for some cancers and pain medicines. Over fishing is also an issue that the oceans are facing and extinction of species like red snapper, blue fin tuna, salmon and many more. Somewhat of a selfish approach, but the pollution and plastic these organisms consume ultimately come back to us when we eat these organisms. Help keeping the oceans clean and pollution free saves the organisms but also protects ourselves. Some of the marine organisms recycle our waste and help keep the environment clean.

Reefs Around the World

Coral Reefs very with size, location, and type.

The Great Barrier reef extends 1,553 miles making it the largest reef in the world located in the coral sea near Australia.

The Red Sea coral reef is 1,180 miles in the Red Sea near Egypt and Israel

Types of Reefs

Fringing: Most common type of reef. These reefs form a type of border the shoreline and grow directly from the shore

Atoll: Is formed from a fringing reef and are in a circular form with an open area (lagoon) in the middle

Barrier: Similar to fringing, they border the shoreline as well but there is a deep section of water between the reef and the shore.



3 thoughts on “The Coral Reef

  1. Very nice article. I like how there was an opposite approach to writing the article from a specific portion in the coral reef ecosystem (the coral itself) to the broader functions, importance, and various other aspects of the coral reef ecosystem.

    I do have one question, are mangroves a part of the coral reef ecosystem or are mangrove forests their own ecosystem that have a symbiotic relationship with the coral reef?

    Liked by 1 person

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