Xylem 6-Series Multiparameter - Manual (Page 328)

Chlorophyll Measurements Appendix I
YSI Incorporated Environmental Monitoring Systems Operations Manual I-1
APPENDIX I CHLOROPHYLL MEASUREMENTS
This is a question and answer guide that will help you optimize performance and trouble-shoot problems.
While the YSI 6025 chlorophyll sensor provides a simple and convenient way to estimate phytoplankton
concentration in the field, there are significant limitations associated with its use that the user should
appreciate fully before beginning field studies. In addition, the chlorophyll systems of YSI 6-series sondes
are characterized by a great deal of flexibility from the point of view of the user. Some examples are
shown below.
ο The data from the chlorophyll sensor can be processed via a sophisticated filtering algorithm that has
variable parameters that are input by the user.
ο
The chlorophyll system can be used in spot sampling applications with a YSI 650 MDS display/logger
or a portable computer.
ο The chlorophyll system can be used on all sondes for long term deployment applications using cable
attachment to a data collection platform.
ο
The chlorophyll system can be used for long-term deployment applications with the YSI 6-series
sondes which contain internal batteries by logging readings directly to sonde memory since they
contain ‘on board’ power.
ο
A number of calibration options are offered with the YSI chlorophyll system.
This section is designed to help the user attain the maximum possible benefit from the YSI 6025
chlorophyll system by supplementing the discussions of chlorophyll provided in other sections of this
manual. (Section 2.1 --Getting Started, Section 5 - Principles of Operation, and Section 2.10 - Care,
Maintenance and Storage). These are questions that may be asked by a typical user of 6-series sondes
with the YSI 6025 chlorophyll sensors. It does not deal with specific instructions for operation of the
sondes at the level presented elsewhere in the manual.
What is the YSI 6025 chlorophyll probe designed to measure?
The YSI sensor is designed to estimate
the phytoplankton content of environmental water. Phytoplankton
concentrations can be useful in predicting detrimental algal blooms and, indirectly, in determining nutrient
loading in environmental applications. The phytoplankton content is estimated by detecting the
fluorescence from the chlorophyll in these species in vivo, i.e., without disrupting the living cells. Note,
however, that the sensor directly measures the fluorescence of all species in the water sample that occurs
when they are irradiated with blue light (centered at about 470 nm). Usually most of the fluorescence is
due to the chlorophyll in the phytoplankton, but it is important to remember that any compounds which are
present in the water sample (either in chemical or biological form), and fluoresce under the optical
constraints of the sensor, will contribute to the readings.
What level of accuracy can be expected in my chlorophyll determinations with the YSI 6025?
YSI feels that the user will attain about the same accuracy with the YSI 6025 as with other commercial
fluorometers that are designed to carry out in vivo determinations of environmental chlorophyll. As for all
measurements of this type, the accuracy will be less than that attained if the user collects water samples and
analyzes them in the laboratory by disrupting cells and quantifying by spectrophotometric or HPLC
analysis of the extracted molecular chlorophyll as described in Standard Methods. The relative accuracy of
the in vivo measurement will be completely dependent on the method of calibration which the user employs
(see next question). No matter what calibration technique is used, however, the readings from the YSI