Ballast water samples which have been filtered through a 10µm nylon mesh usually contain phytoplankton as well as zooplankton organisms. For the detection of viable organisms from both of these two physiological groups different analytical methods may be applied.
Optical counts of the viable organisms are difficult to execute and due to the small size of the organisms demand a high precision microscope as well as additional devices such as compartimented plankton chambers or the Neubauer chamber.
Selective (live-dead) staining methods may be applied to distinguish live cells from dead cells.
The Pulse Amplitude Modulation Fluorometry would describe the physiological status of the micro-phytoplankton organisms and thus indicates, if the phytoplankton organisms in the sample are dead, will probably recover or are viable. However, PAMF does not generate any numerical data.
Flow cytometric analysis will generate numerical data solely for the phytoplankton organisms.
The further development of the Fluorescein-diacetate fluorometry and the Adenosin-triphosphate fluorometry may allow for the transfer of concentration data into numerical data for all viable plankton organisms in the sample.