The environmental impact of paper mill waste discharges to the Upper Medway Estuary, Kent, England

Abstract

The Upper Medway Estuary is considered as the narrow, funnel-shaped channel from the tidal limit at Allington downstream to Lower Upnor. Mathematical models are used to predict the depletion of dissolved oxygen resulting from organic waste inputs to the upper estuary. Surveys of the soft sediment fauna together with sediment redox potentials, organic carbon and cellulose content showed that conditions were generally poor and that faunal diversity was low, although a few surviving oligochaetes proliferated in the absence of predation and competition, with numbers in excess of 1·0 × 10⁶ individuals per m² of sediment being recorded. The bottom sediments were relatively mobile, although a combination of sediment organic content and redox potential profiles clearly demonstrated the occurrence of reduced sediment conditions at depths below 6 cm at some sites in the upper estuary, with the greatest effect at sites downstream of the paper mill discharges. A significant reduction in the amount of organic waste discharged to the upper estuary should increase faunal diversity, although high species richness is considered unlikely given the naturally harsh conditions.