Faunal distributions in soft sediments of the Severn Estuary

The pattern of the infauna on participate shores of the southern coast of the Severn Estuary has been examined. Although mud predominates as the major beach substratum within the Estuary, sand beaches occur in both the lower and upper reaches. Liquid mud is found at l.w. in the middle reaches. Suitability of substratum is shown to be the most important factor influencing animal distribution. The number of infaunal species found in this survey did not increase markedly towards the mouth, in contrast to the pattern displayed by rocky shore animals. Several species were rare or absent on mud beaches close to the entrance of the River Avon and the possibility that sewage contamination is responsible for this is discussed.