Response to lowered nutrient discharges in the coastal waters around the island of Funen, Denmark

The Danish Action Plan for the Aquatic Environment of 1987 prescribes a 50% and 80% run-off reduction of nitrogen and phosphorus, respectively, to the aquatic environment. This is meant to reduce the seriously increasing eutr ophication problems, such as widespread hypoxia and anoxia, in the coastal regions of Denmark. In spite of major investments in sewage treatment, thes e objectives have generally not been realised, primarily because of lack of substantial reductions in nitrogen run-off from diffuse agricultural sourc es. On the island of Funen, Denmark, precipitation in the last two years ha s been extremely low, leading to major decrease in nitrogen and phosphorus run-off to the surrounding coastal waters. For primarily meteorological rea sons, the objectives of the Action Plan were thus fulfilled for the first t ime. Immediate response was registered in the coastal waters around Funen: very low nutrient concentrations during winter 1995/96, higher Secchi depth s, lower phytoplankton production and biomass, increasing depth distributio n of eelgrass (Zostera marina) and higher oxygen concentration in bottom-ne ar water in spring and summer 1996 compared to previous years. This natural 'experiment' suggests that substantially lower nutrient loads to coastal m arine systems can have an immediate, positive impact on oxygen conditions i n bottom-near waters.