The cross-shore distribution of epibenthic predators and its effect on zonation of intertidal macrobenthos: a case study in the river Scheldt

Available research is inconclusive on how circatidal habitat use and cross-shore distribution of aquatic epibenthic predators may affect the vertical zonation of infauna in muddy, soft-bottom substrates in estuaries. We placed fyke traps at different heights on the intertidal mudflat to assess the circatidal density of epibenthic predators. Infauna was sampled across the same tidal gradient. The abundance of epibenthic predators in the fykes decreased with elevation (decreasing inundation time), yet for the shrimp Palaemon longirostris abundance did not change with elevation in autumn. When corrected for inundation time, predator density was equal over the tidal range or higher on the high mudflat in some instances, indicating that predators evenly distributed over the mudflat or moved to the highest part during a high tide. The density of epibenthic predators did not correlate with the density of infauna, whereas the latter did show a close relationship with sediment characteristics. Our data suggest epibenthic predator density does not shape the present distribution of infauna across the tidal gradient on the oligohaline mudflats in the Scheldt.