Modulation of dissolved oxygen levels in a hypertidal estuary by sediment resuspension

Hyperconcentrated benthic layers, which form during neap tides, recruit much of the fine sediment population of the turbidity maximum of a hypertidal estuary. Measurements of tidal amplitude and suspended solids concentration reveal that resuspension of the hyperconcentrated layers occurs between three and eight tides after neap tides rather than during spring tides (12 to 15 tides after neaps). During these resuspension events, dissolved oxygen levels are reduced but recover by spring tides. Peak solids concentrations and critically depressed dissolved oxygen levels are out of phase with tidal current amplitude. Thus observations close to neap and spring tides do not necessaraly capture the extremes of the envelope of water quality conditions.