Dynamic pollution control - time lags and optimal restoration of marine ecosystems

I apply a dynamic model-in linear-quadratic form-to the problem of eutrophication of coastal waters due to nitrogen pollution. The model includes two control measures, one upstream (agricultural abatement) and one downstream (mussel cultivation at the coast). In between, leachates are transported through groundwater and rivers. Groundwater is modelled as a complex system where pollution may decay, but may also be delayed for many years before reentering surface waters and flowing to the sea. Optimal pollution abatement measures are initially intense, declining as the steady state is approached. The decline is more marked for the downstream measure (mussel cultivation) than for agricultural abatement. This is in accordance with results from a simpler theoretical model. Where conditions allow it, mussel cultivation is an economically favourable complement to other forms of nitrogen abatement on the west coast of Sweden. (C) 2003 Published by Elsevier B.V.