| dc.description | Six sandy beaches were sampled on the coast of Ancud, Isla de Chiloé, southern Chile (ca. 42º S) with the following purposes: 1) to study community structure and across shore zonation of the intertidal macroinfauna in relation to different beach types, and 2) to analyze how similar or different is the taxonomic composition and community structure of the macroinfaunal assemblages, compared to those inhabiting sandy beaches located further north of Canal de Chacao, the limit between Isla de Chiloé and the mainland coast. Sediment samples (0.1 m², 30 cm deep) were collected (April-May 1998) with plastic cylinders at fifteen equally spaced levels along three replicated transects (separated by 1 m) extending from above the drift line to the swash zone. The sediment was sieved through a 1 mm mesh and the organisms collected stored in 5% formalin until sorting. To define beach types, the Dean´s parameter was calculated from wave heights and periods, and sand fall velocity of sand particles from the swash zone. The calculations show that one of the sites was a dissipative beach, while the other five had reflective or low intermediate beach characteristics. The highest number of species and total macroinfaunal abundance occurred at the dissipative site (11 species and 59705 ind m-1, respectively), the lowest at the most reflective site (3 species and 507 ind m-1, respectively). In general, the abundance of organisms found were higher than those predicted by a worldwide model of sandy beach community structure. The talitrid amphipod Orchestoidea tuberculata, the cirolanid isopod Excirolana hirsuticauda and the anomuran decapod Emerita analoga, were the most abundant species at all beaches but one. Kite diagrams and cluster analyses show that in general, three faunistical belts occur across the intertidal of the beaches studied. The across shore distribution of the macroinfauna was more related to a sand moisture gradient than to grain size or sediment compactness. Taxonomic composition, community structure and across shore zonation of that macroinfauna were similar to that from beaches located further north of Canal de Chacao | |
