SUBLITTORAL MACROBENTHIC FAUNA OFF PUNTA-COLOSO, ANTOFAGASTA, NORTHERN CHILE - HIGH PERSISTENCE OF THE POLYCHAETE ASSEMBLAGE

Temporal changes in composition and abundance of the sublittoral macro benthic (>0.5mm) polychaete infauna was studied off Punta Coloso, Anto fagasta, for 5 years (1990-1995) at four stations located at depths of 50-60 m. The sandy sediments were sampled with a 0.1 m(2) Petersen ty pe grab. Polychaete contribution to the total fauna was consistently h igh numerically (from 74% to 93%) but more variable in terms of biomas s (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 wor ms Aricidea (Aricidea) sp. n., Magelona phyllisae Jones, Prionospio pe ruana Hartmann-Schroeder, and Tharyx cf. longisetosa Hartmann-Schroede r, and the medium sized Paraprionospio pinnata (Ehlers). Though some s pecies reflected some degree of seasonality, overall temporal fluctuat ion of polychaete abundance does not show annual seasonal cycles but r ather reflects long-term patterns. This study suggests a high stabilit y or persistence over time of the benthic polychaete fauna in spite of the high seasonal variability and interannual fluctuations in oceanog raphic conditions reported for the area. The high faunal affinities re sulting from cluster and ordination analysis indicated the presence of a single and persistent polychaete assemblage.