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REEFS. Kelly Lekan. Early Reefs. First appearance of reefs around 570 million years ago. The first reefs formed were made of cyanobacteria. Were found living around 3.5 billion years ago Reefs formed by trapping in sediment, and secreting calcium carbonate Formed stromatolites

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kelly lekan


Kelly Lekan

early reefs
Early Reefs
  • First appearance of reefs around 570 million years ago.
  • The first reefs formed were made of cyanobacteria.
    • Were found living around 3.5 billion years ago
  • Reefs formed by trapping in sediment, and secreting calcium carbonate
    • Formed stromatolites
  • Reefs were then formed by rugose and tabulate corals
    • Disappeared during the Devonian
modern day reefs
Modern Day Reefs
  • Coral reef building started during the Triassic period
    • Bivalve reefs took over, and then corals became the dominate reef builders after the Cretaceous extinction
coral reefs
‘Rainforests of the Ocean’

One of the most biologically diverse regions

Huge array of species of plant and animal life

Coral Reefs
formation environment
Formation Environment
  • Form in tropical and semitropical areas
  • Water temperatures between 16 and 30 degrees Celsius
  • Exist within 30 degrees latitude north and south of the equator
  • Shallow, clear water
  • Normal salinity free of suspended matter
reef formation
Corals and zooxanthellae algae

Work together in a symbiotic relationship to build reefs

Corals live in colonies


Secrete a hard exoskeleton of calcium carbonate which serves as a base for the reef

Reefs build by the deposition of calcium carbonate

Upper layer is the living layer of the polyps, and when calcium carbonate is secreted, it leaves behind another layer

Reef Formation
types of reefs
Fringing Reefs

Most common type

Project directly offshore of islands or continents

Grow in shallower waters

Barrier Reefs

Occur offshore

Separated by a bay or lagoon


Develop when islands, volcanic, sink and the surrounding reef remains

Types of Reefs

Fringing Reef

Barrier Reef


keys to the past
Keys to the Past
  • Plate tectonics
  • Rise and fall of sea level
  • Extinctions/Interruptive events
plate movement
Plate Movement
  • Plate movement can be seen through the distribution of corals throughout the world
  • When one super continent existed, the Tethys Sea ran through the middle of every continent
    • After American split from Africa and Asia, the Atlantic Ocean formed, and two major areas of coral reef development were formed
      • Caribbean region and the Indo-West Pacific region
  • The distribution of corals today fits the idea of plate tectonics and continental drift
sea level rise and fall
Sea Level Rise and Fall
  • Reefs only grow in warm, clear, shallow water
  • Sea level fluctuation can be studied by the existence or non-existence of coral reefs
  • “The position of fossil reefs in geologic strata are an accurate indicator of sea level at the time of formation of the reef, because reefs will always grow to the level of low tide” (Reef Education Network 2001)
  • 17 cycles of sea level rise and fall over the last two million years
  • Can interpret past environments by the formation of reefs
extinctions and interruptive events
Extinctions and Interruptive Events
  • Reef formations altered by three major extinction events
    • End of the Permian, Triassic, Cretaceous
  • Change in global temperature and a drop in sea level that effected a decrease in reef development
  • Core drilling of reefs
    • Can look at fossils in reefs and determine periods of growth and decline of reefs
significance of reefs
Biologic significance

Home to a huge assortment of plant and animal life

Contain 25% of all marine life

Economic significance



$375 billion contributed to the U.S. economy annually

Artificial Reefs

Significance of Reefs
threats to reefs
Threats to Reefs
  • Natural
    • Weather
    • Natural Disasters
  • Humans
    • The biggest threat to reefs!
    • Fishing with explosives
    • Pollution
    • Global Warming
      • Coral Bleaching
  • Adams, Chuck, Lindberg, Bill, Stevely, John. 2006. The Economic Benefits Associated with Florida’s Artificial Reefs. University of Florida, Institute of Food and Agricultural Sciences.
  • Agardy, Tundi. 2004. America’s Coral Reefs: Awash with Problems. Issues in Science and Technology.
  • Exploring the Environment: Coral Reefs. 2004. Wheeling Jesuit University/NASA supported Classroom of the Future.
  • Reef Education Network. 2001. Life and Times: Origins. University of Sydney and Tech Talk Australia.
  • Solcomhouse. Coral Reefs.
  • Thurman, H.V. 1993. Essentials of Oceanography. Macmillian Publishing, New York. 4th Edition, p. 336-341.
  • Underwater Science Program. 2002. Artificial Reefs of the Florida Keys. Indiana University.
  • United States Environmental Protection Agency. 2007. Coral Reef Protection: About Coral Reefs.
  • United States Geological Survey. 2005. Coral Reef Facts.
  • Weisburd, Steve. 1986. Artificial Reefs. Science News.
  • Wood, Rachel. 2002. Dodging mass extinctions: all around, species were dying off. But in this Devonian reef, like went on. Why? Natural History.
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