An up close view of coral polyps from a reef off the coast of Hawaii displays their bright coloration. This is due to the zooxanthellae, microscopic algae that live within each polyp and provide the coral with much-needed nutrients.

Photograph by Jennifer Bright, MyShot
  • Corals are animals that have the structure of a polyp. Other polyps include sea anemones and Portuguese man o' wars.

    Coral polyps are attached to the substrate. Substrate can be rock, other corals, marine debris, or other hard surface. Coral polyps are firmly attached to the substrate by a feature called a pedal disc.

    A few, dozens, hundreds, and even millions of coral polyps can be attached to an area of substrate. The substrate covered by coral is called a coral branch or coral mound. The community of corals is called a colony.

  • Term Part of Speech Definition Encyclopedic Entry
    colony Noun

    group of one species of organism living close together.

    coral Noun

    tiny ocean animal, some of which secrete calcium carbonate to form reefs.

    coral branch Noun

    area of substrate covered by coral. Also called a coral mound.

    marine debris Noun

    garbage, refuse, or other objects that enter the coastal or ocean environment.

    Encyclopedic Entry: marine debris
    pedal disc Noun

    in a sea anenome or coral, the thin tissue that attaches the animal to the substrate.

    polyp Noun

    a type of animal with a fixed base, a tubelike body, and tentacles for catching prey.

    Portuguese man o' war Noun

    large colony of organisms, resembling a jelly, with venomous tentacles.

    rock Noun

    natural substance composed of solid mineral matter.

    sea anemone Noun

    type of marine animal related to corals and jellies.

    substrate Noun

    base of hard material on which a non-moving organism grows. Also called substratum.