The optimal size of dynamic phosphorus models for coastal areas

One method to assess environmental effects from industrial emissions to coastal and inland waters, e.g. from pulp and paper industries, is to quantify these emissions with mass balance models. In this study six different mass balance models for phosphorus with varying degrees of complexity have been tested in 11 Swedish coastal areas. The majority of these areas are recipients of pulp and paper industries. The accuracy of model predictions of phosphorus and chlorophyll is evaluated and compared between models. The results imply that for the included water bodies, models containing state variables for phosphorus in surface water and deep water are superior to models treating the water column as a completely mixed entity. The results do not justify the separation of phosphorus into dissolved and particulate fractions, but for chlorophyll predictions the results were significantly improved when phytoplankton was included as a state variable. Unless detailed descriptions or predictions of chlorophyll dynamics are required, modelling eutrophication in coastal areas may be considered as a matter of total phosphorus in two water compartments plus sediments.