Abstract
The benthic diatom floras at Clevedon and Weston-Super-Mare [England] were studied over a period of 2 yr, with particular emphasis on the tube-dwelling species. Eight sampling sites were regularly visited, the diatom flora at each recorded and comparison made between the sites on each shore and between the 2 shores. The differences due to seasonal fluctuations in diatom populations, and those due to geographic location are discussed. The type of diatom zonation found during this study may be a result of those conditions peculiar to estuaries and may therefore be typical of estuarine diatom zonation in general.