The basis of this project was the recognition that monitoring is an essential component of any management strategy. Although monitoring is considered by some as old fashioned, it incorporates the contemporary ideas of "continuous real time sampling and analysis", and so still plays a pivotal role in successful management. However, since detailed monitoring is time consuming it often leads to unacceptable time lags between identification of the problem and remedial action. Furthermore time constraints and logistics often limit the number of samples that can be collected and processed. Since multiple samples are often required to evaluate the link between cause and effect. a lack of detail frequently means that limnologists are unable to provide succinct answers to what appear to be simple questions. This leads to poor management options. Our solution to t his problem was to embrace and develop technologies which have the potential to rapidly assess phytoplankton biomass, composition and metabolic state and to bring biological sampling and analysis into the same time frame as the monitoring strategies adopted in fluid mechanics. The objectives of the project as stated in the original application were to evaluate the techniques of flow cytometry and active (dual flash) fluorometry for rapid determination of the biomass, composition and physiological condition of phytoplankton. The background to the project relies on the hierarchy of relationships between light and nutrients which drive photosynthesis, and other metabolic activities and result in cell and population growth (Fig. 1). Active chlorophyll fluorescence and flow cytometry were used to evaluate these processes. Active chlorophyll fluorescence examines phytoplankton at the subcellular and cellular level whereas flow cytometry and the use of fluorescent probes are directed toward the cellular and population levels.