Chemical and mechanical bioerosion of boring sponges from Mexican Pacific coral reefs

Species richness (S) and frequency of invasion (IF) by boring sponges on living colonies of Pocillopora spp. from National Park Isla Isabel (Mexico, East Pacific Ocean) are presented. Twelve species belonging to the genera Aka, Cliona, Pione, Thoosa and Spheciospongia were found, and 56% of coral colonies were invaded by boring sponges, with Cliona vermifera Hancock 1867 being the most abundant species (30%). Carbonate dissolution rate and sediment production were quantified for C. vermifera and Cliona flavifodina Rutzler 1974. Both species exhibited similar rates of calcium carbonate (CaCO3) dissolution (1.2 +/- 0.4 and 0.5 +/- 0.2kg CaCO3 m(-2) year(-1), respectively, mean +/- s.e.m.), and sediment production (3.3 +/- 0.6 and 4.6 +/- 0.5kg CaCO3 m(-2) year(-1)), resulting in mean bioerosion rates of 4.5 +/- 0.9 and 5.1 +/- 0.5kg CaCO3 m(-2) year(-1), respectively. These bioerosion rates are close to previous records of coral calcification per unit of area, suggesting that sponge bioerosion alone can promote disequilibrium in the reef accretion/destruction ratio in localities that are heavily invaded by boring sponges. The proportion of dissolved material by C. vermifera and C. flavifodina (27 and 10.2%, respectively) confirms that chemical bioerosion plays an important role in sponge bioerosion and in the CaCO3 cycle in coral reefs.