The effect of Lithophaga (Bivalvia: Mytilidae) boreholes on the strength of the coral Porites lobata

At Isla del Caño, Costa Rica, the main reef bioeroders are species of the boring bivalve, Lithophaga. These mussels are abundant in virtually all colonies of the main framework builder, Porites lobata. The bivalves have a significant effect on the strength of the colonies which, at a maximum compressive and bending strength of 20 and 5 MN/m2, respectively, are already the lowest ever measured for corals. Presence of bivalve boreholes is inversely logarithmically associated with coral strength, with the greatest decrease in strength occurring with the first boreholes.