Seston transport and deposition in Pelorus sound, south Island, New Zealand

Abstract

Abstract Transport of seston (suspended sediment) in Pelorus Sound is controlled by tides and freshwater inflow. During high freshwater inflow, a moderately stratified estuarine circulation may be superimposed on the tidal circulation, but the latter dominates and transports seston seawards and landwards with the ebb and flood phases respectively. With extreme freshwater inflow, the estuarine circulation gains impetus and most seston is rapidly transported seaward in the low saline surface layer. Irrespective of circulation there is a persistent trend in seston concentrations. Highest values occur at the sound's head because of the influence of nearby Pelorus and Kaituna Rivers and because of resuspension of bottom sediment by strong tidal currents. Seston concentrations wane along the sound until near the entrance, where values increase as a result of greater production of biogenic seston and because additional seston is brought in from Cook Strait with the flood tide. This trend parallels variability in...