Patterns of Spatial Variation of Meiofauna in Sandy Beaches of Northwestern Mexico with Contrasting Levels of Disturbance

Despite the high abundance and diversity of meiofauna in sandy beach habitats, their patterns of spatial distribution have not been well characterized. This study analyzed the horizontal distribution of the intertidal meiofaunal community in sandy beaches of Todos Santos Bay (TSB), northwestern Mexico, and related it with levels of disturbance. Ten sandy beaches were sampled for meiofauna and sediment along the western coast of TSB at lower, mid, and upper levels of the intertidal. The meiofaunal community included five major groups viz. Amphipoda, Copepoda, Nematoda, Oligochaeta, and Polychaeta, and was mostly dominated by nematodes, regardless of the intertidal level. Meiofauna and nematode abundances differed significantly across the beach slope, increasing towards the upper level; this pattern varied along the shoreline, changing particularly where the beach was heavily modified due to costal development. Multivariate analyses significantly differentiated lower, mid, and upper levels of the intertidal, mostly due to differences in copepod abundance. Sediment grain size significantly differed among intertidal levels (i.e., smaller in the upper intertidal) and was negatively correlated with meiofaunal abundance. Moreover, meiofaunal abundance was negatively impacted by the degree of disturbance as highly urbanized/disturbed beaches of TSB showed lower meiofaunal abundance. As costal development continues to increase, findings from ecological surveys should play a pivotal role in characterizing and monitoring the health status of sandy beaches to aid in their management and conservation.