Sample preparation for quantitative autoradiography of phytoplankton [Useful technique for studying species-specific nutrient exchange in microbial communities]

A method of sample preparation for quantitative autoradiography of33PO 4uptake by phytoplankton avoids problems of cell damage and tracer leakage common to earlier techniques. A combination of very brief fixation by Lugol's iodine with collection of cells on polycarbonate filters minimized leakage of tracer while cells remained intact in the preparation of track (thick-layer) autoradiograms. Counting efficiency differed from that in other applications of the track technique, indicating the importance of calibration in quantitative autoradiography. Quantitative yield was consistent among species with the modified technique.