Patterns of abundance and seasonality of polychaetes in SW Atlantic epibenthic shell beds.

JORGE LUIS CEFERINO GUTIERREZ; PALOMO, M. G.; IRIBARNE, O. O.

BULLETIN OF MARINE SCIENCE

Año: 2000 vol. 67 p. 165 - 174

0007-4977

The purpose of this study was to investigate the spatial and temporal distribution of the polychaete species that inhabit shell cavities in beds of the stout razor clam Tagelus plebeius. Samples were taken bimonthly between July 1996, and September 1997, and an additional one was taken in February 1998. The assemblage was dominated by the amphipod Corophium insidiosum and three polychaete species (Laeonereis acuta, Heteromastus similis and Neanthes succinea). The abundance of L. acuta was higher in summer, simultaneously with the occurrence of juveniles. In contrast, C. insidiosum and H. similis were more abundant in winter together with the occurrence of juveniles of the latter species. The predator N. succinea occurred at the end of the sampling period, concurrently with a decrease in all other macroinfaunal taxa. An estimation based on polychaete predation rates indicated that these decreases in macroinfaunal densities may be the result of consumption by N. succinea. Polychaete distribution along the intertidal slope did not vary along the sampling period. Higher density of polychaetes was found in the internal shell sediment than in the sediment outside them. All the evidence suggests that variability in the intensity of species recruitment and direct or indirect biotic interactions may determine the spatial and temporal distribution of macroinfaunal species in these beds.