Reefs
Cavities
The interior of these reefs contain many cavities inside
the coral from the boring by organisms and from the irregular overgrowths
of encrusting organisms. The larger cavities (growth cavities) are due
to biological roofing over chiefly by coral. The cavities inside the reef
contain a distinctive community of organisms. Near the outside, cavity
walls are encrusted with the right valve of the bivalveSpondylus
ictericus, coralline algae, ectroprocts, serpulid tubes and
the red foraminifer Homotrema rubrum. Deep within
the cavities the proportion of wall covered by living organisms decreases
to zero.