Sediment Fluxes in Intertidal Biotopes: BIOTA II

An overview of the field work research projects under the LOIS Biological Influences On interTidal Areas (BIOTA) programme is presented. The main objective of BIOTA is to characterize and quantify fluxes of sediments and the influence of biological components within the intertidal saltmarsh and mudflat zones of the main LOIS study area. Three studies concerned with sediment dynamics and the biota at a variety of sites and salt marsh types on the east coast are described, and a saltmarsh flux study at a single site in Norfolk is briefly outlined (Fig. 1). Some examples of the preliminary research findings are shown with reference to selected sites in the Humber estuary. Regular monitoring of sediment levels out on the sand and mudflats showed remarkable stability, with the amplitude of variation rarely exceeding 5 cm over the four years of measurement. Some sites (generally the more cohesive sediments) displayed a seasonal pattern of elevation change. Oscillations of surface level changes decreased towards the marsh and damping continued with increasing vegetation cover. As expected net accretion generally decreases landward under reduced submergence times, particularly on the open coast marshes; however different sedimentation profiles were observed. In the Humber estuary, net accretion was generally greatest in the middle to lower marsh, with periods of erosion at the seaward edge. The role of vegetation in accretion is complex and may be site specific, affected by a variety of physical factors. The cord grass, Spartina anglica appears to have little effect on sediment deposition, but is more important as a sediment stabilizer during periods of erosion. The types of models that can be derived from the BIOTA study are briefly outlined.