Sponge community structure and disease prevalence on coral reefs in Bocas del Toro, Panamá

Abstract

Sponges are sessile, filter-feeding organisms that are sensitive to both biotic and abiotic components of their environment and are therefore likely to be impacted by environmental stressors. For this reason, sponges are useful as bioindicators of changing environmental conditions. The present study characterized sponge diversity, abundance and disease prevalence on three reefs in Bocas del Toro, Panama. The reefs were similar in general characteristics, however, one site was located just offshore of a village where anedoctal reports suggest that "black water" outflow (sewage, road pollution, and solid waste dumping) occurs. Overall, 51 species and 2532 individual sponges were identified. Analysis of similarity indicated significant differences in sponge community structure between the sites. The site nearest Saigon village had significantly fewer species per quadrat, although total number of individuals and number of individuals per quadrat were similar between this site and the more distant, upstream site (Punta Caracol). Evenness (J) and diversity (H') were significantly reduced at Saigon, as was the slope of the species-area curve. Dominant species also differed among sites, with the most abundant species at Saigon considered rare at the two upstream sites. Only Niphates erecta was among the five most dominant species at all three sites; Aplysina fulva, which dominated the upstream sites and is known to be sensitive to stress, was rare at Saigon, and Chondrilla nucula, another stress-intolerant species, was only dominant at Casa Blanca. Hymeniacidon sp., on the other hand, dominated the reef only at Saigon. Aplysina red band syndrome (ARBS) was present at all three sites, but prevalence was higher and more variable at Saigon. Differences in sponge community structure and disease prevalence