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Ecology of Coral Reefs

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

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  1. Ecology of Coral Reefs Spring 2012 Mariana Freitas

  2. Introduction • 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.

  3. 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”.

  4. Importance of Coral Reefs • Home to numerous organisms • Protection and shelter • Increase the diversity • Food • Control of carbon dioxide • Barrier to coasts and shore

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. Types of Reefs • Atoll – circular reef surrounding a lagoon.

  10. Reproduction • 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).

  11. Zooxanthellae • 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.

  12. Diseases • 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.

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

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

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

  16. Diseases • 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.

  17. 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.

  18. Threats and Destruction • Global warming • Overfishing • Tourism • Water contamination • Increase CO2

  19. Conclusion • 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.

  20. References • http://oceanworld.tamu.edu/students/coral/coral5.htm • http://plaza.ufl.edu/bettie/coralreef.html • http://coris.noaa.gov/about/diseases/ • 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

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