Numerical modelling of phytoplankton biomass in coastal waters

This paper introduces an effective tool for monitoring phytoplankton in open waters. In this study, phytoplankton is the principal component together with salinity and temperature for describing the water dynamics in the Danish marine waters. A major obstacle for accurate monitoring of phytoplankton (chl-a) is the very dynamic nature of phytoplankton and the water masses encompassing the algae. This can be overcome by combining the very coarse temporal resolution data from the traditional monitoring programme to validate hydrodynamic modelling together with remote sensing. DHI Water and Environmentʹs 3D modelling tool MIKE 3, which is a dynamical ecological model, has been applied to the Danish marine waters covering the Baltic sea through the inner Danish straits and extended to the North Sea. MIKE 3 is a commercially available software system that has been used in a wide variety of applications concerning 3D studies of hydrodynamics in the marine environment. MIKE 3 is an operational system with quick, less expensive and easily accessible assessments of the state and development in phytoplankton with appropriate scaling of resolutions. The paper concludes that a combination of traditional monitoring with ship, dynamical modelling of hydrodynamics and eutrophication in combination with remote sensing of chl-a concentrations of surface waters offers the ideal tools to enhance the temporal and spatial description of large water bodies. The results presented cover the period January to September 1999. The 3D model is verified and calibrated using in situ measurements from various monitoring stations in the Danish marine waters and validated against satellite images from SeaWiFS. The data basis for this study has been two national programmes both related to the monitoring of the coastal environment.