Temporal and spatial distributions of moisture and organic contents acrossa macro-tidal mudflat

The purpose of this study was to make comprehensive surface measurements of the changes in moisture and organic contents across the Skeffling mudflats (Humber Estuary, UK) and to examine the effects of exposure and location o n the sediment properties. Sediment cores were collected using modified 50 mi syringes, and the data compared with measurements of chlorophyll a and c olloidal carbohydrate concentrations. The temporal and spatial relationship s between these surface sediment properties were quantified and related to the measured critical erosion shear stress. Moisture and organic contents c orrelate significantly with respect to morphology, both across the mudflat and with depth below the sediment surface, These variations affected the di stributions of bulk density and sediment erodibility, although these two va riables were not directly related. The relatively coarse vertical resolutio n of the cores prevented clear relationships being identified between criti cal erosion shear stress, moisture and organic contents, and the chlorophyl l a and colloidal carbohydrate concentrations. Analysis of mean values remo ved some of the spatial variability and a reasonable exponential relationsh ip was obtained between erosion shear stress and colloidal carbohydrate. Th is paper highlights the influence of the physical, morphological and biolog ical characteristics of the surface sediment upon its erosion resistance. T he implications for the development of the surface morphology and mudflat a re considered. (C) 2000 Elsevier Science Ltd. All rights reserved.