Cnidarians (coral, sea anemones, jellyfish and their allies) have a range of life cycles, which often include a period in the water column, as adults (e.g. jellyfish) or as transient microscopic larvae (most cnidarians). Many cnidarians also reproduce asexually (e.g. corals). Pelagic medusoid and larval forms are present in the waters surrounding Heron Island Reef year round. Cnidarian larvae settle and typically metamorphose into benthic juveniles, which grow into either microscopic or macroscopic adults with a wide range of life styles. Benthic cnidarians are some of the most obvious animals on the reef (i.e. hard coral). They exist in almost all reef habitats, including the beach rock, the inner and outer reef zones, rubble crest, the seaward platform, reef slope and the deeper inter-reefal zone.
reef zones of the southwest end of Heron Island Reef
(Image provided by Digital Globe Inc and Biophysical Remote Sensing Group, The University of Queensland)