MACROINFAUNAL ASSEMBLAGES ASSOCIATED WITH MUSSEL AND CLAM BEDS IN AN ESTUARY OF SOUTHERN CHILE

Samples were collected from September 1990 to February 1992, at three subtidal sites of the middle reaches of the Queule River estuary, sout hern Chile, to analyze the spatial and temporal variability of the mac roinfauna inhabiting substrata with different abundances of bivalves. In addition, water and sediment samples were obtained to study the rel ationships between the temporal variability in macroinfaunal abundance s, physical factors, and chlorophyll a content. Temperature, salinity, and chlorophyll a showed a rather strong seasonal variability but sli ght between-site differences. Sediment characteristics and bivalve abu ndances, by contrast, exhibited little temporal variability but large differences between sites. The macroinfauna was primarily represented by polychaetes, Prionospio (Minuspio) patagonica being dominant in the three areas. Most dominant species showed similar trends of temporal variability, with maximum abundances recorded during spring and fall. The appearance of recruits was restricted to the summer with little di fference among sites. Multiple regression analyses showed that the tem poral variability of macroinfaunal adults and recruits, was primarily associated with variability in salinity and water temperature, respect ively. Spatial variability of these organisms was also explained by va riations in these factors, together with those of sediment texture and organic matter content. No evidence of interactions (significant rela tionships) was found between the abundances of bivalves and those of t he macroinfauna, nor among macroinfaunal organisms.