Restoration of a Disused Dock Basin as a Habitat for Marine Benthos and Fish

(1) Changes in the water quality, and in flora and fauna, of a Liverpool dock have been monitored since closure of its gates in 1977. Water salinities have been found to fall within the ranges 25-31%o, and temperatures 03-19 OC. Secchi disc extinction depths averaged 5-6 m in the dock and 10 cm in the Mersey estuary outside. An air-lift pump has been installed which prevents stratification during summer and ensures an oxygenrich water column. The absence of harmful dinoflagellate blooms is attributed to artificial destratification by this method. (2) Improvements in water quality have been accompanied by the development of a more diverse marine flora and fauna than in other unclosed docks. The benthic community is dominated by Mytilus edulis. Trace metal concentrations and coliform bacterial counts in Mytilus flesh are sufficiently low for the animals to comply with existing food safety regulations. Introduced Laminaria saccharine grew until water temperatures reached 15 OC, but a few plants survived a 14-week period in summer 1981 when ambient water temperatures were above 15 ?C. (3) It is concluded that a dock of this character can be maintained as a productive marine environment with a variety of educational, amenity and economic uses.