Long-term study of an estuarine mudflat subjected to petro-chemical discharges

The Kinneil intertidal area, situated in the middle reaches of the Forth estuary, eastern Scotland, has been subject to the effects of industrial discharges, principally from petro-chemical industries (oil refinery and chemical works) since the 1920s. The intertidal fauna has been studied annually since 1976 using consistent methodology (90 stations, each with two samples of 5 × 5 × 5 cm, through a 250 μm sieve). The study continues, now providing over 20 yr of data. During the study period the discharges from the industrial sources have been reduced substantially through a combination of plant closure and modernization and the installation of effluent treatment works. Furthermore, the River Avon which flows across the area has experienced substantial improvements in water quality, attributed to improvements in waste treatment works at localities upstream from the estuarine site. Fluctuations of the faunal composition of the mudflats have been studied over the period. Some species, such as Hydrobia ulvae, Cerastoderma edule, and Nereis diversicolor show substantial fluctuations but no clear trend, whilst others such as Corophium volutator, Macoma balthica and Eteone longa show clear increases in abundance. Overall, however, the clearest trends have been increases in diversity, expressed either as mean number of species per station, or as diversity indices. These increases in diversity are shown to be a clear community response to the improvements made to the petro-chemical wastes discharged to the area.