Pieces of coral rubble (Porites porites), collected from across 3 fringing reefs that lie along a eutrophication gradient, were examined for the presence of clionid sponges. A similarity analysis of species composition showed that reef zone had less effect on clionid community composition than did other factors affecting the reefs as a whole. Except on the back reef, the Lones, distances, and depths within the reefs had no significant influence on the number of clionid invasions. Reef comparisons demonstrated that clionid abundance increased with increasing eutrophication. Clionids were found in 41% of the pieces collected from the most eutrophic site vs. 24% from the least eutrophic. Because clionids are the principal bioeroders of coral reefs, any increase in their abundance will likely result in greater bioerosion rates. The mean abundance of Type 3 corals (in which fragmentation is the primary mode of propagation) is positively related to the frequency of boring sponge invasion. suggesting that increased bioerosion may be partly responsible for community shifts toward Type 3 corals in polluted waters. Cliona cf. vastifica, found for the first time in Barbados, flourishes on the most eutrophic reef and may become an important bioeroder under the highly eutrophic conditions that have begun to plague West Indian reefs. Two new species of Cliona (Porifera: Hadromerida: Clionidae) are described.