Patterns of distribution of the polychaete fauna in subtidal soft sediments of the Ría de Aldán (north-western Spain)

The composition and spatial distribution of the polychaete fauna on the subtidal soft sediments of the Ria de Aldan (Galicia, north-western Spain) were studied by means of quantitative sampling and multivariate analysis. Thefaunal distribution was mainly conditioned by a sediment gradient defined by decreasing grain size, from the mouth towards the inner margins of the ria. The coarse and medium sand fauna was mainly dominated bypisionids, spionids and syllids. Finer sediments (fine sand to mud) showed a greater abundance of paraonids, spionids and cirratulids and deposit feeding species. The greatest number of species and diversity were found in coarse sediments.