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Nutrients are serious marine pollutants. Scottish Highland and Island salmon farming has grown dramatically over the last fifteen years, and is predicted to reach 125,000 metric tonnes this year. Until now, its overall contribution to nutrient pollution has been unquantified. On the 31st August 2000, OSPAR, the responsible international inter-governmental body, published guidelines for calculating nutrient losses for aquaculture. The application of these guidelines in this report indicates for the first time the full extent of nutrient pollution from Scottish aquaculture: this year some 7,500 tonnes of nitrogen, comparable to the annual sewage inputs of some 3.2 million people; and 1,240 tonnes of phosphorous, comparable to that from 9.4 million people. In 1997 Scotland’s population was 5.1 million. This obviously presents risks in what were relatively pristine waters. Nutrients stimulate plant growth. It is known from other parts of Europe that they may affect important Highland and Island habitats such as seaweed forests and eelgrass meadows, where the cloudiness of the water resulting from increased phytoplankton, and the proliferation of epiphytes on the surface of these larger plants, reduces the depth to which forests and meadows can grow. The major economic threat comes from the proliferation of toxic blooms. Evidence has accumulated, especially in the last few years, that increases in nutrients, and the distortion of nutrient ratios, result in an increased risk from toxic blooms, both in their frequency of occurrence and their geographic extent. This includes Amnesic Shellfish Poisoning, ASP, responsible for the major closures affecting scallop …