The main objective of this survey was to assess the impact of the major discharge, Cliff Quay Sewage Treatment works on the intertidal fauna of the Orwell Estuary. All twenty five sites were located between Cliff Reach and Shotley Point. A sediment sample was collected at each site for particle-size analysis and organic carbon content determination. Data from sites 1, 4, and 24 are missing from the survey report. In a preliminary survey, the upper estuary had been described as faunistically impoverished, suffering from over-dominance of a few species, in particular Tharyx sp and the tubificids. Contrary to the preliminary survey, no major trends in intertidal species diversity were found along the length of the estuary. Species assemblages were found to be related to the percentage of clay, the percentage of silt and the mean particle size of the sediment. Very high levels of abundance were recorded in the upper estuary, the dominant species being Tubificoides pseudogaster.
