Véronique Cornet-Barthaux

Using a new fluorescent probe of silicification to measure species-specific activities of diatoms under varying environmental conditions

A new method is presented that enables distinguishing between active and non-active cells with regard to biogenic silica deposition during frustule formation in natural communities of siliceous phytoplankton. The PDMPO method is based on the fluorescence of biogenic silica after incubation with the probe. Only those cells that have been depositing silica (by adjunction of intercalary plates during the cell cycle or by depositing a new frustule valve upon cell division) exhibit a typical fluorescence that is proportional to the amount of biogenic silica deposited. This new method has several advantages; it is easy to use at sea, very sensitive, and samples can be conserved for several months without major loss of fluorescence. This method offers new possibilities of investigation of ecophysiological controls within the natural diatom community and will also bring more information to the new generation of sophisticated multi-element multi-species biogeochemical models.