Geographic patterns of coral bioerosion: a productivity hypothesis

T'he numbers of boring bivalves in corals in large museum collections were used to indicate relative bioerosional damage to the corals. The proportion of corals from different locations that contain boring bivalves is highly correlated with global patterns of plankton primary productivity. The densities of five other, non-boring, groups of planktivores associated with the same corals are similarly correlated with productivity. The proportion of corals containing boring bivalves and the number ot" boring bivalves per coral head can be ranked by region as follows: eastern Pacific > western Atlantic > Indian Ocean > western Pacific. This ranking also corresponds to primary productivity differences. Measurements of the basal, margin of live tissue, and maximum circumferences of the coral heads indicate that western Atlantic massive corals have more of their skeletal surface exposed to borers, i.e. not covered by live tissue, than do indo-Pacific corals. Consequently, the former also have weaker basal attachments which suggests that they are more likely to be dislodged during storms. The reason why massive corals in the western Atlantic te