Coral rubble is the most common hard substrate on coral reefs. Distribution, abundance, and diversity of cavity dwellers (coelobites) that live on rubble undersides in the Florida Reef Tract is largely controlled by (1) flushing of sub-rubble cavities, (2) rubble stability, and (3)
interactions between organisms. Diversity and abundance of coelobites in terms of cover are different in the major reef environments. They are highest around the marginal reefs and lowest in the fore reef. Bryozoa, the foraminifera Homotrema rubrum, and vermetid gastropods are most
abundant around the reef environment. Crustose coralline algae and polychaetes appear to be most abundant in the back reef. The abundance of sponges decreases from the back reef towards the fore reef. Crustose coralline algae are the most abundant organisms in terms of cover and worms in terms
of individuals. Bryozoa have the highest diversity with 28% of the 67 invertebrate species identified. Diversity and abundance (cover and number of individuals) increase with rubble size. Cover is also positively correlated with relative amounts of flushing of subrubble cavities, which is
largely a function of water depth. Lateral variations in environmental influence due to higher outflow of Florida Bay water towards the reef tract through wide channels between the Middle Keys, the impact of Hurricane Andrew and tropical storm Gordon on the Upper Keys' reefs, and the anthropogenic
influence due to extensive collection of rubble (“live rock”) off the Middle Keys are not reflected in the coelobite communities. There were no differences detected in coelobite abundance and diversity between reefs off the Upper, Middle, and Lower Keys. The results support the
few previous large-scale studies that suggest the existence of a coelobite zonation in reefs. However, the findings indicate that coelobites are of limited use as indicators of environmental and anthropogenic impact.
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