Abstract. The redevelopment of disused docks around Liverpool into areas suitable for shops, offices, housing and recreational watersports has necessitated the maintenance of good water quality in these areas. The main source of water to the docks is the River Mersey, which contains high concentrations of nutrients, encouraging algal blooms ‐ including potentially nuisance species ‐ in the enclosed dock basins. Since 1988 an extensive monitoring programme has been run sampling the hydrography, plankton and benthos of the docks. During this period there has been an improvement in water quality, including a reduction in summer phytoplankton biomass and anoxic bottom water. There are strong indications that phytoplankton biomass has been severely reduced by the filter feeding of Mytifus edulis. Changes in the composition of the benthic community since 1988 suggest that the large population of M. edulis is now suffering from limited recruitment. The long‐term development and stability of the system is discussed with reference to community succession and its link to ecosystem functioning.

ABSTRACT1. The use of redeveloped docks for the conservation of lagoonal communities is considered with particular reference to the South Docks in Liverpool.2. Redevelopment of the previously derelict South Docks since 1981 has created a semi-enclosed, brackish body of water by dredging of dock basins that were filled with silt. The development of biological communities on the walls and in the sediments of these docks has been studied.3. A reasonably diverse flora and fauna was established on the walls within approximately six years, but a persistent sediment-dwelling community has not yet developed.4. Over 90 species of macroflora and macrofauna have been recorded from the South Docks to date. Three of these species are considered to be lagoonal specialists. 5.Considerations for the management of docks as a resource in the conservation of lagoonal communities are discussed.

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