Several invertebrates, including sponges, tunicates, and other cnidarians overgrow living corals. Among the most common organisms are the boring sponge, Cliona spp. and the colonial tunicate, Trididemnum solidum.

The sponge, Cliona spp. overgrowing a branch of elkhorn coral.

 

A colonial tunicate Trididemnum, overgrowing mountainous star coral, (M. faveolata).

Encrusting gorgonian Erythropodium caribaeorum overgrowing starlet coral Siderastrea siderea

Encrusting gorgonian, Erythropodium caribaeorum overgrowing a colony of star coral, Montastraea annularis. The gorgonian has caused some tissue loss that is evident at the interface between the gorgonian and live tissue.

Another important source of mortality to stony corals, especially massive and plating species, is competition with faster growing fleshy algae.