Sponge diversity in Eastern Tropical Pacific coral reefs: an interoceanic comparison

Sponges are an important component of coral reef communities. The present study is the first devoted exclusively to coral reef sponges from Eastern Tropical Pacific (ETP). Eighty-seven species were found, with assemblages dominated by very small cryptic patches and boring sponges such as Cliona vermifera; the most common species in ETP reefs. We compared the sponge patterns from ETP reefs, Caribbean reefs (CR) and West Pacific reefs (WPR), and all have in common that very few species dominate the sponge assemblages. However, they are massive or large sun exposed sponges in CR and WPR, and small encrusting and boring cryptic species in ETP. At a similar depth, CR and WPR had seven times more individuals per m(2), and between four (CR) and five times (WPR) more species per m(2) than ETP. Perturbation, at local and large scale, rather than biological factors, seems to explain the low prevalence and characteristics of sponge assemblages in ETP reefs, which are very frequently located in shallow water where excessive turbulence, abrasion and high levels of damaging light occur. Other factors such as the recurrence of large-scale phenomena (mainly El Nino events), age of the reef (younger in ETP), isolation (higher in ETP), difficulty to gain recruits from distant areas (higher in ETP), are responsible for shaping ETP sponge communities. Such great differences in sponge fauna between the three basins might have consequences for coral reef structure and dynamics.