Modelling the dispersion of harmful algal bloom (HAB) in the Thermaikos gulf (NW Aegean Sea)

Coastal hydrodynamics are directly related to important environmental and ecological issues. This
paper focuses on the study of harmful phytoplankton cells’ dispersion, after an episode of an algal
bloom, based on mathematical modeling. The case of Thermaikos Gulf was used for the simulation.
The necessary hydrodynamic information was obtained by the application of a 2D hydrodynamic
model directly coupled with a transport model for the simulation of the harmful cells’ dispersion. The
model describes hydrodynamic and biological processes such as advection, dispersion and cell
growth and losses. The mechanical processes are described with the mass and momentum
conservation equations while the movement of the particles is described with the Random Walk
simulation. The biological processes of cell growth rate were described as a function of temperature
light and nutrients, and embodied to the simulation as input data for the model runs while the
biological losses are simulated by the removal of particles randomly selected from the field. The
reliability of the model was tested using data of a real algal bloom episode. Finally the study is
completed with the detection of the distribution of the harmful phytoplankton cells in Thermaikos for
different wind conditions and different sources of algal bloom.