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Ecology of Coral Reefs. Spring 2012 Mariana Freitas. Introduction. Coral reefs are unique ocean ecosystems in that they have extremely high productivity and diversity. Also called tropical r ain forests of the o cean because of their diversity. Phylum Cnidaria.

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Ecology of coral reefs

Ecology of Coral Reefs

Spring 2012

Mariana Freitas


  • Coral reefs are unique ocean ecosystems in that they have extremely high productivity and diversity.

  • Also called tropical

    rain forests of the

    ocean because of

    their diversity.

Phylum cnidaria
Phylum Cnidaria

  • Corals are part of a group of small aquatic animals called “Cnidarians”. Other Cnidarians are sea anemones, hydroids and jellyfish.

  • Corals are a very diverse group and they are made up of many tiny organisms living together in a colony, and each individual organism is called a “polyp”.

Importance of coral reefs
Importance of Coral Reefs

  • Home to numerous organisms

  • Protection and shelter

  • Increase the diversity

  • Food

  • Control of carbon dioxide

  • Barrier to coasts and shore

Environmental conditions
Environmental Conditions

  • Certain conditions are necessary in order for a coral reef to form.

  • Temperature, light, salinity, sedimentation and wave energy all play a crucial role in reef development.

  • Reefs grow best in sunny, shallow, clear water.

Environmental conditions1
Environmental Conditions

  • Temperature - minimum temperature of 18°C and a maximum temperature of 32°C

  • Shallow – bordering land at depths of less than 27 meters

  • Clear – sunlight necessary for zooxanthellae to perform photosynthesis

  • Salinity - require a salinity between 34 and 37 parts per 1000

Types of reefs
Types of Reefs

  • There are three kinds of coral reef: the fringing reef, the barrier reef and the atoll.

  • Fringing reef – develop in shallow waters along the coast of tropical islands or continents. They grow right up to sea level.

Types of reefs1
Types of Reefs

  • Barrier reef – separated from the shore by a wide, deep lagoon. They grow only when there has been a change of sea level on the adjacent coast.

Types of reefs2
Types of Reefs

  • Atoll – circular reef surrounding a lagoon.


  • Corals can reproduce both sexually and asexually.

  • Asexually reproduction may occur by budding or fragmentation.

  • Sexually reproduction occurs either by internal or external fertilization.

  • Some corals are hermaphroditic (both female and male reproductive cells).


  • Symbiotic relationship with corals in which both organisms benefit from each other.

  • Zooxanthellae is an unicellular algae that lives in the gastrodermis of reef building corals.

  • The algae supplies oxygen and other nutrients that allow corals to grow and reproduce.

  • Corals give carbon dioxide and other substances that algae needs.


  • Coral diseases can occur in response to biotic stresses or abioticstresses.

  • The rate of incidences has been increasing rapidly over the last 10 years.

  • Some of the causes include poor water quality (human pollution) and increase of surface temperatures.


  • Black-band disease (BBD) - blackish concentric or crescent-shaped band; cyanobacteria has been primarily associated with this disease and also sulfide-oxidizing bacteria.


  • White band disease (WBD) – complete degradation of coral tissue in Caribbean acroporid corals. Usually proceeds from the base of colony to branch tips.


  • White plague – similar to WBD; sharp line between apparently healthy coral tissue and freshly exposed coral skeleton.


  • White pox – white circular lesions; tissue degradation occurs rapidly.

  • Yellow band - large rings or patches of bleachedyellow tissue; loss of tissue is slow.

  • Dark spots – dark, brown or purple pigmented areas; tissue loss is minimal.

Threats and destruction
Threats and Destruction

  • Both natural and human related causes.

  • 10% of the world’s coral reefs have already been destroyed.

  • Scientists predict that in the next 20-40 years, 70% of the coral reefs will be lost, if no changes are made by human population.

Threats and destruction1
Threats and Destruction

  • Global warming

  • Overfishing

  • Tourism

  • Water contamination

  • Increase CO2


  • Coral reef ecosystems are one of the most valuable ecosystems on Earth.

  • They are incredibly diverse, very productive, but also extremely fragile.

  • They provide food, protection of coasts, and shelter to many marine organisms.

  • Serious threats include climate change, fishing and pollution.





  • Introduction to the Biology of Marine Life, Ninth Edition by John F. Morrissey and James L. Sumich

  • Ecology: The Experimental Analysis of Distribution and Abundance, Sixth Edition by Charles J. Krebs

  • Marine Ecology: concepts and applications, by Martin Speight and Peter Henderson

  • Marine Ecology, Oxford by Sean D. Connell and Bronwyn M. Gillanders

  • Marine Community Ecology, First Edition by Mark D. Bertness, Steven D. Gaines, Mark E. Hay