Improvement of the shallow water communities following reductions of industrial outlets and sewage discharge in the Hvaler estuary,Norway

Three years' investigations of the shallow water communities at 30 different rocky shore sites in an estuary in southeast Norway were carried out during 1980–1982. The flora was mostly poor, possibly due to a combination of fresh water exposure, industrial and sewage outlets. The aim of these investigations was to establish the environmental status of the estuary prior to huge outlet reductions in 1989/90. Later reinvestigations during 1992–1994, following a significant reduction of titanium dioxide wastes and building of a new chemical sewage treatment plant have shown an improvement of the macroalgal and benthic animal communities. In the formerly most polluted area, the number of benthic taxa has increased since 1980–1982 by 50–350% in 1992–1994.