Influence of biota on spatial and temporal variation in sediment erodability and material flux on a tidal flat (Westerschelde, The Netherlands)

Abstract

Annular flumes were used to quantlfy benthic-pelaqc exchanges in relation to changes in current velocity and sediment biota. Various physical, chemical and biological parameters were determined for 4 sites on the Molenplaat tidal flat in the Westerschelde (The Netherlands) during 2 field campaigns in May-June and August-September 1996. These Pcluded: the mass of sediment eroded, maximum and mean erosion rates, critical erosion velocity (Ucfi,), suspension feeding/biodeposition rate, oxygen and ammonium fluxes, density of macrofauna species, chlorophyll a (chl a), colloidal carbohydrate, and physical properties of the sediment. The study showed marked and statistically significant spatial and temporal differences in the potential for sediment erosion. Sites in the centre of the tidal flat were less erodable than those on the edge. All sites on the tidal flat had a significantly (p < 0.001) lower erosion potential in June (i.e. higher U,,, and lower erosion rates) compared to September.