Meiofauna distribution along a gradient of sandy beaches in northern Spain

Ten sandy beaches located in northern Spain were studied during the summer of 1999 to analyse the patterns in number of major taxa, abundance and biomass of meiofauna along a gradient of morphodynamic beach types and exposure rate. Sediment samples were collected with metallic cylinders (23 cm2 cross-sectional area, 120 cm long) at 10 equally spaced shore levels along six replicated transects extended from the drift line down to the low tide level. Wave exposure rate and Dean’s parameter were estimated at each sampled beach. The meiofauna was primarily represented by Nematoda and Harpacticoidea. Meiofaunal abundances ranged between 64 106 and 296 106 ind.m 1, whereas biomass (ash free dry weight) per linear meter of beach ranged between 30 and 166 gm 1. The results showed two significant trends: (1) the meiofaunal biomass increases exponentially with exposure rate from exposed to very exposed beaches; and (2) the number of major taxa increases exponentially with exposure rate and linearly with average grain size. These trends are opposite to the general patterns of the sandy beach macroinfauna, which is generally negatively affected by increases in wave exposure and grain size. This suggests that macro- and meiofauna are affected in different ways by the physical processes associated with wave action.