Temporal variation of polychaete assemblages and their bioturbation potential in subtidal sedimentary bottoms

Temporal variation patterns and bioturbatory activity of polychaete assemblages have been insufficiently studied. Two subtidal fine-sediment sites have been sampled in order to describe and compare polychaete temporal variation patterns. In order to estimate bioturbation potential (BP), a new approach is proposed that aims maximum versatility for comparative studies. Both assemblages differed significantly in terms of temporal variation of sedimentary and faunal attributes. The most exposed site was dominated by species characteristic of muddy-fine sand and presented a seasonal pattern with higher densities and BP values from mid-summer to early winter. The most sheltered and muddy site was dominated by Paradoneis lyra and presented an irregular temporal variation. Signs of moderate organic enrichment were found, particularly in the less exposed site. Spatial and temporal variations appear to be related to sediment features and hydrodynamic stress, which also affect BP of each assemblage. Our results suggest that the bioturbatory activity of polychaetes is more extensive and relevant in finer sediments.