Boring sponges and the modeling of coral reefs in the east Pacific Ocean

Abstract

A total of 900 coral fragments collected across 2 fringing reefs located southwest of Mexico, La Entrega (LE) and San Agustín (SA), were examined for the presence of boring sponges. Of all samples, 43% were invaded by boring sponges, and 7 species belonging to 5 genera (Aka, Cliona, Pione, Cliothosa and Thoosa) were identified. The most abundant species were Cliona vermifera (17.9%), Cliona sp. (10.8%), A. cryptica (7.8%) and P. carpenteri (6.0%). The distribution and abundance of the species varied considerably throughout the reef area (margin and platform) and displayed certain selectivity for specific calcareous substrata. C. vermifera, Cliona sp., A. cryptica and P. carpenteri were most common on the reef margins, while T. calpulli was common on the central platform. A. cryptica, P. carpenteri, and Cliothosa hancocki were frequently found living in the immediate vicinity of live coral tissue, contrary to C. vermifera, T. calpulli and Cliona mucronata, which preferentially bored coral rubble. The results showed that reef margins had a significantly higher infestation level than the platforms (mean infestations of 60.6 and 26.2%, respectively). There were also differences between reefs. The infestation was higher on LE than on SA (48.6 and 38.2%, respectively), and these differences were larger between the platforms of the 2 reefs (41.3 and 11.1%, respectively). In general, the results of the present study have demonstrated that the diversity and abundance of species, as well as the infestation of coral frameworks by sponges, was significantly higher in the margin at both reefs studied and on the platform of LE, where the availability of exposed carbonate substrate was higher. In the margin of these reefs, the consequences of boring went far beyond the mere hollowing out of a few cavities, since by weakening the coral's attachment to the substrate, the sponges accelerated coral loss and restructured the reef edge. This pattern may have important implications for the preservation of the reef framework. © Inter-Research 2008.