Ballast water monitoring device

A system comprising:

• a ballast water treatment system;
• and
• a ballast water monitoring device comprising:
• a chamber for receiving a sample;
• at least one light source to emit light towards the sample;
• a light detector to receive light from the sample and generate a light signal;
• and
• a controller configured to:
• control the at least one light source to emit a single pulse of light with a duration of up to 450 μs,
• calculate the variable fluorescence [Fv] of the sample in response to the pulse of light, at time intervals less than the duration of the pulse of light,
• compare the calculated variable fluorescence to a predetermined reference limit, and
• when the calculated variable fluorescence is greater than the predetermined reference limit the ballast water monitoring device controls the ballast water treatment system to eliminate live phytoplankton cells.

A method of determining whether live phytoplankton are present in a sample, the method comprising:

• generating a pulse of light with a duration of up to 450 μs and directing it towards the sample;
• receiving a light from the sample in response to receiving the pulse of light, and generating a light signal;
• calculating the variable fluorescence [Fv] of the sample in response to receiving the pulse of light at time intervals less than the duration of the pulse of light;
• comparing the calculated variable fluorescence to a predetermined reference limit;
• and
• performing an action when the calculated variable fluorescence exceeds the predetermined reference limit.