A numerical analysis of counts of diatom frustules, and other algae, in water samples from the River Wey

During May 1978, samples of water were collected from 24 sites on, or associated with, the River Wey between its source south of Haslemere and Send just downstream of Guildford (approx. 57.5 km). Counts of diatom frustules, and other algae surviving the sampling technique, were analyzed by numerical taxonomic techniques. On the basis of community structure, the river was clearly separated into two regions. The seven sites along the first 18 km formed a cluster, and those of the remaining stretch formed a second cluster, which was more similar to Broadwater, a large shallow pond that discharges into the river between Godalming and Guildford (approx. 34.2 km below the source). Two methods are compared for reducing the counts obtained for each sample to a single index.