Bottom sediment variability in the active layer of the inner shelf off the Ebro Delta

Abstract

The variability of the bottom sediment grain size was estimated at two sites located at 8.5 and 12.5 m depth across the Ebro Delta inner shelf from cores taken at the beginning and end of three one-month-long current meter + turbidimeter deployments. The sediment variability showed different characteristics in each survey. During winter conditions and after a river flood (December '96-January '97), a mud layer was deposited on the inner shelf overlying sandy deposits. The mud layer was eroded before April '97. During the spring survey (April '97-May '97) a sand layer was deposited after several storms. Finally, a general coarsening of the sediment was observed during the summer deployment (August '97). Potential implications of these sediment changes in the estimation of near bottom sediment fluxes are addressed, considering effects on turbidity measures and the estimation of the vertical profile of suspended sediment.