PHYTOPLANKTON MONITORING BY FLOW-CYTOMETRY

The application of flow cytometry to the monitoring of phytoplankton i s demonstrated. A comparison is made with conventional approaches to p hytoplankton monitoring: light microscopy for the determination of spe cies abundance, and chlorophyll a determination and in situ chlorophyl l a measurement by fluorescence for the determination of the biomass. Flow cytometric measurements correlate well with these conventional ty pes of measurements, as has been shown by comparing a full year of mon itoring data obtained at a fixed monitoring location 10 km off the Dut ch coast. Flow cytometry bridges the gap between labour-intensive, but highly informative, microscopic observations and simple biomass measu rements with less information content: via flow cytometry optical data are obtained at high speed for individual particles, which can be tra nslated into biomass information. On the basis of the flow cytometric measurements, rough discrimination of phytoplankton species groups is possible, particularly for the abundant species. Of crucial importance is careful calibration of the flow cytometer, to ensure quantitative and comparable measurements over a long period of time. Calibration an d quality assurance aspects are covered in detail.