Spartina Salt Marshes in Southern England: II. Rate and Seasonal Pattern of Sediment Accretion

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Abstract
Direct measurement and stratigraphical evidence confirmed that accretion up to 8-10 cm per year occurred regularly on Spartina marsh at Bridgwater Bay. It is estimated that silt is deposited at a rate of about 500 m3/ha/year on this 35-year-old marsh which was originally established by planting. Older, naturally established marshes in Poole Harbour are accreting much more slowly at present and the reasons for this difference are discussed. A distinctive seasonal pattern of accretion was found at Bridgwater Bay. Statistical analyses suggest that rise in accretion should be considered as related to a general factor associated with increasing height of marsh and height and weight of vegetation and decreasing vegetation density, rather than to any one of these factors specifically. A regression equation is given which enables estimates of accretion at any point on the Bridgwater Bay marsh to be made.