Comparison of phytoplankton successions in two eutrophic lakes by flow cytometry

Flow cytometry is an effective tool for the study of algal ecology, physiology and toxicology. It allows for multi-parameter analysis of individual cells on the basis of light scattering properties, indicating cellular complexity, and fluorescence. Flow cytometry has been widely used in oceanography to quantify and sort heterogeneous algal populations and more recently in the development of bioassays for marine and freshwater algae using toxicity tests based on growth inhibition. Fluorescence emission characteristics may be especially useful in classifying blue-green algae (cyanobacteria) as they contain phycoerythrin (550-600 nm emission), chlorophyll a (650-700 nm emission) and allophycocyanin (660 nm emission). The basis of this work was to assess the utility of flow cytometric analysis for the rapid identification and sorting of freshwater algae and cyanobacteria species, with particular emphasis on the Rotorua lakes. Using a selection of laboratory cultured freshwater algae and cyanobacteria species, this study demonstrated unique light scatter and fluorescent characteristics for each species examined. These properties allowed for rapid sp ecies identification and sorting of mixed populations of laboratory cultures and Rotorua lakes water samples. Further analysis of lake water samples collected over time demonstrated changes in abundance and community composition that may be useful in future examination of seasonal changes in lake dynamics.