Monitoring cell‐specific neutral lipid accumulation in Phaeodactylum tricornutum (Bacillariophyceae) with Nile Red staining – a new method for Flow CAM

With the fluorescent stain Nile Red ( NR ), phytoplankton lipid accumulation can be monitored quickly and in situ. In the light of recent results in phytoplankton diversity research, there is also a need for cell‐ and species‐specific lipid measurement techniques. The objective of this work was to investigate whether cell‐specific phytoplankton lipid accumulation could be monitored with the image‐based particle analyzer Flow CAM ™ and NR staining. Applying Phaeodactylum tricornutum as a model species, we compared the Flow CAM method to two established lipid quantification methods: spectrofluorometric NR fluorescence measurement and total lipid analysis by gas chromatography. The experiment was carried out in batch cultures under nitrogen limitation to induce lipid accumulation. We showed significant correlation between the three different lipid quantification methods confirming the applicability of the novel Flow CAM method in cell‐specific and near real‐time lipid quantification. Furthermore, with the method described here, the lipid content of taxonomically distinguished cells can eventually be measured from multispecies cultures, opening several new possibilities to study species‐specific responses to stress conditions and the complementarity effect.