region, south-east Sulawesi, Indonesia: richness and abundance

The in£uence of sedimentation, depth and substratum angle on sponge assemblages in the Wakatobi region, south-eastern Sulawesi, Indonesia was considered. Sponge assemblages were sampled from two reef localities.The ¢rst reef (Sampela) was highly impacted by high sedimentation rates with ¢ne sediment particles that settle slowly, while the second (Hoga) experienced only fast settling coarse sediment with lower overall sedimentation rates. Sponge assemblages were sampled (area occupied and numbers) on the reef £at (0m) and at 5 (reef crest), 10 and 15m (15m at Hoga only). Some signi¢cant (P50.001) di¡erences were observed in the area occupied and the number of sponge patches between surface angles and sites. Signi¢cantly lower (t44.61, df9, P50.001) sponge numbers, percentage cover and richness were associated with the reef £at at both sites compared with all other depths at each site, with the exception of abundance of sponges on the reef £at at Sampela, which was much greater than at any other depth sampled. Species richness increased with depth at both sites but di¡erences between surface angles were only recorded at Sampela, with higher species richness being found on vertical, inclined and horizontal surfaces respectively. A total of 100 sponge species (total area sampled 52.5m2) was reported from the two sites, with 58 species found at Sampela and 71 species at Hoga (41 % of species shared). Multi-dimensional scaling (MDS) indicated di¡erences in assemblage structure between sites and most depth intervals, bu