We currently deploy three types of sensors which measure Phycoerythrin fluorescence. These are summarized in the following table:
|Click sensor name for link to manufacturer website||Turner Designs Cyclops 7||Turner Designs CyanoWatch||JFE Advantch MultiExciter|
|Excitation Wavelength||515 – 547 nm||595 nm||Multiple1|
|Detection Wavelength||> 590 nm @ 90 degrees||670 nm @ 90 degrees|
|Accuracy||larger of +/- 0.2 ug/L or 3% reading||+/-0.2% FS|
|Sensor Format||Flow through||Flow through||Outward looking|
1The multi-exciter excites at 9 different wavelengths and uses the resulting fluorescence “fingerprint” to estimate the types of phytoplankton present.
Calibration Evaluation: The phycoerythrin sensors are uncalibrated and report phycoeryhrin flourescence in relative fluorescent units (RFUs). Data from these sensors are therefore not directly comparable, both between sensor types and even between deployments of individual sensors of the same sensor type.
Current quality control protocols attempt to ensure that within individual sensor deployments data are relatable. Periods of sensor offset drift or fouling are identified and corrected for.
Protocols to allow for the direct comparison of data from different sensors and sensor types are in development. In addition past and future field efforts include work to relate/calibrate the sensor readings to concentrations of phycoerythrin and/or to cell number. Upgrades to the database to more accurately display data (only comprable data on the same plot) and to allow for access to field calibrated data are also underway.
Turbidity Artifact: The phycoerythrin (PE) sensors that we have deployed have a significant turbidity artifact. This artifact is sometimes so extreme that it often exceeds the signal due to PE-containing cells. Without correction, the data from these sensors can be difficult to interpret. This artifact is estimated and removed from the phycoerythrin signal as part of the quality control process. Click here for additional details. In general, the CyanoWatch is less affected by turbidity at low turbidity levels, but does have an artifact at higher turbidity levels. The turbidity artifact is sensor specific and details of the individual corrections can be found in the QA/QC archive below.
Phycoerythrin QA/QC Archive
|Link or PDF with details||Dates||Description|
|s1pe-01||8/17/11 – 8/28/11||filter for instrument noise|
|s3 blog entry||9/28/11||Blog entry evaluating some issues with sensor baseline/behavior|
|s3pe-01||8/17/12 – 3/1/13||CyanoWatch: signal filter for noise (CyanoWatch sensor)|
|s3pe-02||8/1/20 – 3/1/21||QC: correction for drit & turbidity artifact|
|s9pe-01||4/12/19 – 1/11/20||Corrections for turbidity-artifact using 12-hour data windows|