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, southern Chile, to analyze the spatial and temporal variability of the macroinfauna inhabiting substrata with different abundances of bivalves. In addition, water and sediment samples were obtained to study the relationships between the temporal variability in macroinfaunal abundances, physical factors and chlorophylla content. Temperature, salinity, and chlorophylla showed a rather strong seasonal variability but slight between-site differences. Sediment characteristics and bivalve abundances, by contrast, exhibited little temporal variability but large differences between sites. The macroinfauna was primarily represented by polychaetesPrionospio (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 difference among sites. Multiple regression analyses showed that the temporal variability of macroinfaunal adults and recruits, was primarily associated with variability in salinity and water temperature, respectively. Spatial variability of these organisms was also explained by variations in these factors, together with those of sediment texture and organic matter content. No evidence of interactions (significant relationships) was found between the abundances of bivalves and those of the macroinfauna, nor among macroinfaunal organisms.