| dc.description | Three sandy beaches located in southern Chile (Gaviotas, Guabún and Mar Brava; ca. 42º S) were studied during the summer of 2000 to analyse the patterns in abundance and biomass of the meiofauna along a gradient of morphodynamic beach types. Sediment samples were collected with metallic cylinders (23 cm² cross sectional area, 120 cm long) at ten equally spaced tidal levels along six transects separated between 5 and 10 m and extending from above the drift line down to the low tide level. Porosity, shear strength, water content, penetrability and grain size of the substrate were measured in each sampling level. The meiofauna was primarily represented by Nematoda and Copepoda Harpacticoidea. The highest average density and biomass per unit of area were found at the reflective beach of Gaviotas (6,172 ind 10 cm-2 and 2.38 g m-2, ash free dry weight) as compared with the intermediate beach of Guabún (3,390 ind 10 cm-2 and 1.70 g m-2) and the dissipative beach of Mar Brava (3,667 ind 10 cm-2 and 0.86 g m-2). Total abundance and biomass of the meiofauna per linear meter of beach (i.e., total meiofauna in an intertidal across-shore transect 1 m wide) were higher at Mar Brava (506 x 10(6) ind m-1 and 119.4 g m-1), as compared with Gaviotas (271 x 10(6) ind m-1 and 101.7 g m-1) and Guabún (143 x 10(6) ind m-1 and 73.9 g m-1). Therefore, these last results show a trend of increasing intertidal meiofaunal abundances and biomass towards the dissipative stage of the beach gradient analyzed. The highest meiofaunal densities and biomass occurred at the upper and mid shore levels of each beach. Lower across-shore variability in density and biomass were found at the dissipative beach. Results of a Monte Carlo permutation test showed that water content, penetrability and grain size were the best predictor variables of meiofaunal density. Body sizes of nematodes, copepods, turbellarians, halacarids and ostracods were correlated with sediment characteristics. In general, the relationship between community structure of the meiofauna and beach morphodynamics, were similar to that found for the macroinfauna from different sandy beaches around the world, suggesting that meiofauna and macroinfauna are similarly affected by the physical processes associated to different beach types | |
