Limpet erosion of chalk shore platforms in southeast England

Where the Upper Chalk reaches the coast in East Sussex it gives rise to hig h cliffs and wide shore platforms. Limpets (Patella vulgata) living on the platforms contribute significantly to platform downwearing by ingesting cha lk as they graze and by excavating hollows (homescars) to which they return after feeding. A series of experiments has been carried out to try to esti mate rates of limpet erosion. Analyses of the calcium carbonate content of the faeces of captive limpets suggest that adult limpets consume about 4.9 g of chalk per year. On the platforms as a whole limpets are probably respo nsible for an average of about 0.15 mm of surface lowering a year, but in a reas of high population density the rate may be as high as 0.49 mm a year. The overall mean rate of platform lowering caused by all processes of weath ering and erosion is estimated to be about 2.3 mm a year across the entire intertidal zone, but where limpets are present in significant numbers the r ate may be around 1.3 mm a year. The implication is that limpets are respon sible for an average of about 12 per cent of the downwearing in the areas t hey frequent, and in areas of maximal population density may cause 35 per c ent or more of the downwearing in their vicinity. Subsidiary experiments are described that assess the limitations of the fae cal method of estimating limpet erosion. Copyright (C) 2000 John Wiley & So ns, Ltd.