FOSFORMODELLER FÖR FISKODLING I SÖTVATTEN / Phosphorus mass balance models for freshwater fish farms
Existing mass balance models for phosphorus were tested for fish farm emissions in eight Northern and Central European lakes. These traditional models overestimated the total phosphorus concentration in these lakes by on average a factor of two. Data from the eight lakes were therefore used to calibrate emission specific models based on the Vollenweider and Dillon-Rigler structures. With this approach, it was possible to improve the accuracy of the models and to eliminate systematic errors. The new models gave r2 values ranging between 0.90 and 0.92. It was not possible to detect any differences in phosphorus-chlorophyll relationships between lakes with or without fish farm emissions. Neither were there any significant differences between measurements in farm lakes and results obtained from phosphorus-chlorophyll models found in the scientific literature. In the future, however, data from more lakes will be needed to further test the new models and to investigate other effect parameters, e.g. phytoplankton biomass and hypolimnetic oxygen concentrations.