MODELING THE GROWTH OF CYANOBACTERIA (GROWSCUM)

Toxic cyanobacteria have become a common nuisance in freshwater lakes and reservoirs throughout the world. some times resulting in the closu re of sites with high amenity value. Cyanobacteria are able to regulat e their buoyancy state in response to changing photosynthetic rates. A dditionally, the cyanobacteria are liable to become entrained within w ind-induced near-surface turbulent currents, resulting in mixing and m ass transport. These movement processes have been modelled. A mathemat ical function is presented which describes light- and nutrient-limited cyanobacterial growth. The growth model is integrated with a previous movement model (SCUM: simulation of cyanobacterial underwater movemen t) as movement patterns and wind-induced lake mixing strongly affect t he intensity and duration of light received by the cyanobacteria and t hereby determine the photosynthetic potential. Results of the model su ggest that cyanobacteria are resistant to periods of lake mixing and c ontinue to increase their biomass, but at a depressed rate. Growth is most rapid under calm conditions. The results agree well with field-ba sed findings, confirming the validity of the growth function.