Structure and secondary production of the macrobenthic community in an aquatic transition environment of the Gulf of Olbia, Mediterranean Sea

216-226The composition and the secondary production of the macrobenthic community of Rio Padrongiano Delta (the Gulf of Olbia, Tyrrhenian Sea) was investigated. Three sites (L, S and C) were sampled quarterly for macrofauna; environmental variables were measured monthly at each site. A total of 115 taxa, representing 9 phyla were identified. Data were subjected to univariate and multivariate analyses to discriminate among sites. Two-way ANOVA indicated that abundance N and other community measures (H’, Δ* and Δ⁺) differed greatly among sites. Two sites were numerically dominated by Polychaetes (54.6% and 58.3% of total abundance, respectively), while, at the third site, they represented only 24.1%. Molluscs made the greatest contribution to the community biomass at all sites, accounting for 96%, 89.4% and 80.7% of the total biomass, respectively. Benthic production was estimated by an indirect method. Mean annual secondary production of macrobenthic community varied among 8.5, 23.8 and 94 g/m²/yr. Differences among sites were mostly dependent on the different contribute of an invasive mussel, Musculista senhousia. Musculista senhousia seems to facilitate other macrobenthic taxa and seems to have a fundamental role on secondary production of the macrobenthic community