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

Abstract

The 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.