Ecology and distribution of soft-sediment benthic communities off Viti Levu (Fiji)

Information on biodiversity and community structure is vital for monitoring the effects of climate change and other anthropogenic impacts. Benthic ecosystems of 5 sites off Viti Levu (Fiji), comprising 50 stations were sampled quantitatively revealing 13 128 individuals of 230 species at a mean density of 273.5 ind. m -2 . Common taxa included polychaetes (89 species), crustaceans (84 species), molluscs (50 species) and echinoderms (7 species). No species occurred in all 50 stations; the maximum distribution range was 45 stations occupied by the polychaete Aglaophamus sp. A total of 81 species (35.2%) were restricted to single sites ('uniques'), highlighting spot endemism. Species richness and rarefaction curves provided high estimates of diversity. Multivariate analyses incorporating biological abundances and environmental factors showed 3 distinct clusters among sites characterising differences in benthic community structure. Strongest determinants of faunal distribution were depth, distance from reef and river, and sand content. The presence of heterogeneous faunal assemblages suggests the interplay of these factors at each site. Fauna in Nadi Bay (Shannon-Weiner diversity index H ': 3.26), Suva Harbour (H ': 3.19) and Laucala Bay Lagoon (H ': 3.06) had high diversity indicative of biologically accommodated communities. Rewa River Estuary (H ': 2.42) and Nukubuco Reef drop-off (H ': 2.48) had low diversities, typical of habitats subjected to fluctuating environmental conditions. Benthic community structure in the lagoons around Viti Levu was rich and diverse. Biodiversity was greater than previously recorded from the Great Astrolabe Reef, Fiji (207 to 211 species) and Australia's Great Barrier Reef (154 species), but lower than in New Caledonia (311 species) and Tahiti (315 species).