Seasonal and interannual variability in population abundances of the intertidal macroinfauna of Queule river estuary, south-central Chile

Sediment samples were monthly collected at Queule river estuary (ca. 39 deg rees S), south-central Chile, from October 1990 to April 1992, and from Sep tember 1995 to November 1997 to study temporal variability in population ab undances of the macroinfauna inhabiting sandy and muddy-sand intertidal sub strates. Sandy sediments had higher percentages of sand particles and lower percentages of mud particles, biogenic aggregates and total organic matter than muddy-sand sediments. The same macroinfaunal species were found at bo th sites. That macroinfauna was dominated by polychaetes: the spionid Prion ospio (Minuspio) patagonica Augener 1923, the capitellid Capitella sp. and the nereid Perinereis gualpensis Jeldes 1963, Other common organisms were t he amphipod Paracorophium hartamannorum Andres 1975 and the small bivalve K ingiella chilenica Soot-Ryen 1959. The highest abundances of the total macr oinfauna usually ocurred during summer months (January-February), The most abundant species was P. (M,) patagonica (up to 130-140,000 ind m(-2) in the muddy-sand sediments). During some months, this species had significantly higher abundances at the muddy-sand sediments. A similar trend is that show n by P. hartmannorum; i.e., significantly higher abundances at the muddy-sa nd sediments (up to 75,000 ind m(-2)). During many months, the population a bundances of Capitella sp. and K. chilenica were significantly higher at th e sandy site. The highest population abundances of Capitella sp. were close to 37,800 ind m(-2) (February 1991 and February 1996), while the maximum v alues for K. chilenica ranged from 13.000 to 14,000 ind m(-2) (February 199 1 and November 1995, respectively). The population abundances of P. gualpen sis (with the exception of the period October 1995-January 1996) were simil ar at both sites. Interannual comparisons of macroinfaunal abundances carri ed out for the sandy site showed no significant differences among years for the total macroinfauna and for all the species, but P. gualpensis. No sign ificant differences among years were found for the total macroinfauna, P. ( M.)patagonica, P. gualpensis and P. hartmannorum at the muddy-sand site. On the other hand, the abundances of Capitella sp. and K. chilenica differed significantly among years. Significant differences among months within annu al periods were found for the total macroinfauna and species population abu ndances at the sandy and muddy-sand sites, The temporal variability of the macroinfauna did not have any significant relationship with the temporal va riability in sediment characteristics.