Abstract: The invention relates to a method and an apparatus for detecting living phytoplankton cells and/or microorganisms in or out of water, particularly ballast water, bodies of water, sewage, or water in swimming and bathing devices. Said method is characterized by the following steps: the variable fluorescence (Fv) is calculated by forming the difference between the maximum fluorescence (Fm) and the minimum fluorescence (Fo) in a measuring space or detecting part or all of the dynamic shape of a fluorescence induction curve in a measuring space, particularly measuring; and calculating the number of living phytoplankton cells and/or microorganisms of a reference species in the measuring space in accordance with the variable fluorescence (Fv).

Abstract: The invention related to a method and an apparatus for detecting living phytoplankton cells and/or microorganisms in or out of water, particularly ballast water, bodies of water, sewage, or water in swimming and bathing devices. Said method is characterized by the following steps:—the variable fluorescence (Fv) is calculated by forming the difference between the maximum fluorescence (Fm) and the minimum fluorescence (Fo) in a measuring space or detecting part or all of the dynamic shape of a fluorescence induction curve in a measuring space, particularly measuring; and—calculating the number of living phytoplankton cells and/or microorganisms of a reference species in the measuring space in accordance with the variable fluorescence (Fv).