Recent applications of flow cytometry in aquatic microbial ecology.

Microorganisms (unicellular algae, bacteria) constitute fundamental compartments of aquatic ecosystems because of their high concentrations and activities. The evaluation and understanding of their behavior and role raise different problems for which traditional methodologies are often inadequate, whether they refer to global or classical microscopic analyses. Flow cytometry (FCM) has been recently used to study microorganisms in aquatic environments. Although this technology is still applied on a limited scale in our field, a large number of works has been done showing that FCM seems to be a promising tool for aquatic microbial ecology. This paper summarizes, from the literature produced during the last decade and with original data obtained in our laboratory, the main questions related to the cell identification, the evaluation of cell viability, biomasses and productions and the measurements of bacterial and phytoplanktonic activities. The representatives of sampling and observation scales is also discussed within the framework of the FCM measurements.