In situ autofluorescence detection of a fouling marine diatom on different surfaces

A new technique for quantifying fouling diatoms adhering to different surfaces was developed and tested. The method is based on recording the in vivo chlorophyll autofluorescence of diatom cells in situ. The enhanced signal obtained after addition of DCMU was used as a biomass estimate, and the enhancement itself as an indicator of the photosynthetic capacity. A fluorescence spectrometer equipped with a “well plate reader”; accessory was programmed to scan predetermined positions on the microscope slide based test surfaces. In standard tests, a matrix of 7 × 25 equidistant locations was applied to record the central 17 × 67 mm² area of the test surface. Thus, both spatial distributions and the mean value of chlorophyll associated with the specified area could be obtained directly. Microscopical counting was performed for calibration on transparent glass surfaces as well as PVA‐SbQ based hydrogels. There was a good correlation between counting and fluorescence recordings, with a linear range up to 1100 cells mm^?2. Due to the inherent inaccuracies of background estimates, the detection limit on glass and gel was approximately 200 cells mm^?2. The method was also applied successfully to test non‐transparent surfaces. In addition to standard mass screening of different test surfaces, the method may be found useful in studies of algal physiology related to cell adhesion, photosynthesis, growth, detachment and spatial migration.