Sponges (Porifera) distribution along a depth gradient in a coral reef, Parque Nacional San Esteban, Carabobo, Venezuela.

Abstract

Sponges constitute one of the most diverse and abundant animal groups in the marine tropical benthos especially in coral reefs, though poorly studied to species level. The aim of this study is to characterize the sponge community along a depth gradient at Isla Larga (Parque Nacional San Esteban, Venezuela) fringe reef. Net and total sedimentation, roughness index, sponge species richness, density and proportion of the bottom covered by sponges, were evaluated at seven depths (1, 3, 6, 9, 12, 15, 18m), 17 species were identified grouped in 10 demosponges families. The highest densities and coverage corresponded to 6m of depth (6.03ind/m2; 11%), that coincides with the lowest net sedimentation and highest substrate heterogeneity. Most abundant species were Desmapsamma anchorata, Amphimedon erina and Scopalina rueztleri. Principal component analysis divided this community in three zones according to depth. The shallow zone of the reef (1 and 3m), where wave force and high irradiance exert a constant “stress sponges, shows the lowest density and coverage by sponges. In contrast, medium depth (6, 9 y 12m) and deep zone (15 y 18m) with lower light and sedimentation levels seem to enhance sponge growth and survival that are reflected on the higher densities and coverage of sponges.