Organ pipe coral
Pillar coral
Pipe coral
Cavernous star coral
Organ Pipe Coral
The rocky structure that make up coral reefs are actually a build-up of calcium secreted by coral polyps.
Photograph by Robert Sisson
  • ANIMALS
  • PHOTO GALLERY

Coral

See coral pictures in this photo gallery from National Geographic.

October 20, 2009

Related Topics

  • REEFS
  • CORALS

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