Meio- and macrofauna assemblages in tourist-oriented sandy beaches of the northern Gulf of Oman: the effects of trampling.

Tourist trampling is a major anthropogenic disturbance affecting sandy beaches. In this field study, we investigated how varying intensities of tourist trampling and sediment depth influence the diversity and abundance of intertidal meio- and macrofaunal benthic assemblages in the Gulf of Oman. Both taxonomic and functional structures were assessed. A total of 4599 invertebrate specimens representing 41 families were identified. Tourist trampling significantly reduced family richness (F = 51.03, p < 0.0001) and total abundance of fauna (F = 40.24, p < 0.0001) as well as biodiversity metrics of the assemblages. The composition (Pseudo-F = 44.87, p < 0.001) and structure (Pseudo-F = 33.39, p < 0.001) of faunal assemblages also varied as a factor of trampling intensity. Differences in the abundance of Opheliidae, Cymothoidae, or Orbiniidae contributed mostly to the observed changes in assemblages. Beta partitioning analysis indicated less species replacement and more hierarchical loss. Responses of the trophic guild assemblages followed a nearly similar pattern. Both subsurface deposit feeders and surface/subsurface dwelling carnivores were found to be significantly affected by trampling density. The sediment depth significantly affected the diversity indices of trophic guild assemblages. More diverse assemblages were detected in the bottom layer. Depth-related compositional and structural variations were indicated by higher abundances of Talitridae and Gammaridae, subsurface-deposit feeders, and surface-herbivorous-benthic meio- and macrofauna in deep layer. This study provides evidence that tourist-related trampling is a key driver of biodiversity loss and structural simplification in sandy beach macrobenthic assemblages.