A novel phytoplankton chlorophyll technique: toward automated analysis

Interest in the <1 μm picoplankton fraction of natural waters, especially the oligotrophic oceans, has generated a trend toward the use of smaller and smaller porosity membrane filters for particulate analyses. The controversy concerning the suitability of glass fiber versus membrane filters for retaining chlorophyll-containing parlicles is re-examined and the inadequacies of filtration discussed. Previous comparisons in the literature fail to resolve this controversy as tests were performed in waters of >1.0 μm/l chlorophyll. A novel phytoplankton chlorophyll technique for fresh and marine waters is described which eliminates the need to concentrate plankton on filters. Two commercially available instruments have been modified to permit fluorescence measurements of whole water extracts. The lower limit of detection is 0.1 μg/l in situ concentration or 0.02 μg/l extract concentration. The technique lends itself well to automation with particular applications to in situ fluorometry, flow cytometry and continuous chlorophyll determinations.