Sublittoral Macrobenthic Fauna off Punta Coloso, Antofagasta, Northern Chile: High Persistence of the Polychaete Assemblage

Temporal changes in composition and abundance of the sublittoral macrobenthic (>0.5 mm) polychaete infauna was studied off Punta Coloso, Antofagasta, for 5 years (1990–1995) at four stations located at depths of 50–60 m. The sandy sediments were sampled with a 0.1 m² Petersen type grab. Polychaete contribution to the total fauna was consistently high numerically (from 74% to 93%) but more variable in terms of biomass (from 16% to 78%). The number of invertebrate species collected per cruise was relatively low (44–90 species) and the number of polychaete species ranged from 29 to 36 (overall cumulative number = 45 species). The mean abundance of polychaete per station ranged from 1,666 to 41,620 ind.·m⁻², and the overall abundance varied from 9,025 to 19,130 ind.·m⁻². The polychaete mean biomass ranged from 0.29 to 36.98 g (AFDW)·m⁻² and the overall biomass fluctuated from 2.39 to 11.35 g·m⁻². The most abundant polychaete species included the small sized worms Aricidea (Aricidea) sp. n., Magelona phyllisae Jones, Prionospio peruana Hartmann-Schroeder, and Tharyx cf. longisetosa Hartmann-Schroeder, and the medium sized Paraprionospio pinnata (Ehlers). Though some species reflected some degree of seasonality, overall temporal fluctuation of polychaete abundance does not show annual seasonal cycles but rather reflects long-term patterns. This study suggests a high stability or persistence over time of the benthic polychaete fauna in spite of the high seasonal variability and interannual fluctuations in oceanographic conditions reported for the area. The high faunal affinities resulting from cluster and ordination analysis indicated the presence of a single and persistent polychaete assemblage.