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Chlorophyll Measurements Appendix I
YSI Incorporated Environmental Monitoring Systems Operations Manual I-4
Will the chlorophyll values determined in vivo with the YSI 6025 be reportable for compliance
purposes?
Probably not. Because of the limitations on the method outlined above and in the
Section 5, Principles of
Operation , there is always inaccuracy in the in vivo method. It might be possible to work with a particular
regulatory agency to develop specific correlation protocols between in vivo and laboratory-determined
chlorophyll values for a particular site, but generation of this methodology is left to the user.
I have seen molecular chlorophyll standards advertised. Can these be used to calibrate the YSI 6025
sensor?
Probably not. The standards are usually only soluble in organic solvents such as acetone that would cause
serious damage to the materials used in the YSI 6025 probe. Even if molecular chlorophyll standards that
are soluble in aqueous media were available, their fluorescence is not likely to emulate
in vivo chlorophyll
fluorescence any better than the dye standard described above.
Caution : Do not expose the YSI 6025 to calibrant solutions involving any solvent other than water or very
dilute aqueous acid mixtures. Damage to the sensor under these conditions will not be covered under
warranty.
The Standard Methods procedure generates values designated as “chlorophyll a”. Is this species the
reporting unit for the YSI 6025?
No. The different types of chlorophyll cannot be differentiated by the YSI 6025, or by virtually any
in vivo
fluorometer. The values from the YSI 6025 should be reported either as relative fluorescence units or in
ug/L of general chlorophyll as long as the method of determination (and its limitations) is specified.
Is the YSI 6025 sensor linear with regard to changes in phytoplankton content?
Yes. The sensor is very linear as evidenced by the following plot that shows the results of a serial dilution
of a laboratory algae sample. This linearity on a particular algal species maximizes the ability of the sensor
to track relative phytoplankton changes from site to site or during a monitoring study.